diff --git a/addons/point_of_sale/controllers/main.py b/addons/point_of_sale/controllers/main.py
index 833b6e32c1c..9b359da4db7 100644
--- a/addons/point_of_sale/controllers/main.py
+++ b/addons/point_of_sale/controllers/main.py
@@ -5,6 +5,7 @@ import werkzeug.utils
 
 from odoo import http
 from odoo.http import request
+from odoo.osv.expression import AND
 
 _logger = logging.getLogger(__name__)
 
@@ -12,18 +13,31 @@ _logger = logging.getLogger(__name__)
 class PosController(http.Controller):
 
     @http.route('/pos/web', type='http', auth='user')
-    def pos_web(self, **k):
-        # if user not logged in, log him in
-        pos_sessions = request.env['pos.session'].sudo().search([
-            ('state', '=', 'opened'),
-            ('user_id', '=', request.session.uid),
-            ('rescue', '=', False)])
-        if not pos_sessions:
+    def pos_web(self, config_id=False, **k):
+        """Open a pos session for the given config.
+
+        The right pos session will be selected to open, if non is open yet a new session will be created.
+
+        :param debug: The debug mode to load the session in.
+        :type debug: str.
+        :param config_id: id of the config that has to be loaded.
+        :type config_id: str.
+        :returns: object -- The rendered pos session.
+        """
+        domain = [
+                ('state', '=', 'opened'),
+                ('user_id', '=', request.session.uid),
+                ('rescue', '=', False)
+                ]
+        if config_id:
+            AND([domain,['config_id', '=', int(config_id)]])
+        pos_session = request.env['pos.session'].sudo().search(domain, limit=1)
+        if not pos_session:
             return werkzeug.utils.redirect('/web#action=point_of_sale.action_client_pos_menu')
-        pos_sessions.login()
+        pos_session.login()
         # The POS only work in one company, so we enforce the one of the session in the context
         session_info = request.env['ir.http'].session_info()
-        session_info['user_context']['allowed_company_ids'] = pos_sessions.company_id.ids
+        session_info['user_context']['allowed_company_ids'] = pos_session.company_id.ids
         context = {
             'session_info': session_info
         }
diff --git a/addons/point_of_sale/models/pos_config.py b/addons/point_of_sale/models/pos_config.py
index 0ba6baa7d1e..f247a2fecbb 100644
--- a/addons/point_of_sale/models/pos_config.py
+++ b/addons/point_of_sale/models/pos_config.py
@@ -226,10 +226,13 @@ class PosConfig(models.Model):
             else:
                 pos_config.currency_id = pos_config.company_id.currency_id.id
 
-    @api.depends('session_ids')
+    @api.depends('session_ids', 'session_ids.state')
     def _compute_current_session(self):
+        """If there is an open session, store it to current_session_id / current_session_State.
+        """
         for pos_config in self:
-            session = pos_config.session_ids.filtered(lambda s: s.state != 'closed' and not s.rescue)
+            session = pos_config.session_ids.filtered(lambda s: s.user_id.id == self.env.uid and \
+                    not s.state == 'closed' and not s.rescue)
             # sessions ordered by id desc
             pos_config.current_session_id = session and session[0].id or False
             pos_config.current_session_state = session and session[0].state or False
@@ -467,13 +470,19 @@ class PosConfig(models.Model):
 
     # Methods to open the POS
     def open_ui(self):
-        """ open the pos interface """
+        """Open the pos interface with config_id as an extra argument.
+    
+        In vanilla PoS each user can only have one active session, therefore it was not needed to pass the config_id
+        on opening a session. It is also possible to login to sessions created by other users.
+        
+        :returns: dict
+        """
         self.ensure_one()
         # check all constraints, raises if any is not met
         self._validate_fields(set(self._fields) - {"cash_control"})
         return {
             'type': 'ir.actions.act_url',
-            'url':   '/pos/web/',
+            'url':   '/pos/web?config_id=%d' % self.id,
             'target': 'self',
         }
 
@@ -495,7 +504,6 @@ class PosConfig(models.Model):
             })
             if self.current_session_id.state == 'opened':
                 return self.open_ui()
-            return self._open_session(self.current_session_id.id)
         return self._open_session(self.current_session_id.id)
 
     def open_existing_session_cb(self):
diff --git a/addons/point_of_sale/models/pos_order.py b/addons/point_of_sale/models/pos_order.py
index 49ffd4ecb68..de36a06468d 100644
--- a/addons/point_of_sale/models/pos_order.py
+++ b/addons/point_of_sale/models/pos_order.py
@@ -48,6 +48,7 @@ class PosOrder(models.Model):
             'amount_tax':  ui_order['amount_tax'],
             'amount_return':  ui_order['amount_return'],
             'company_id': self.env['pos.session'].browse(ui_order['pos_session_id']).company_id.id,
+            'to_invoice': ui_order['to_invoice'] if "to_invoice" in ui_order else False,
         }
 
     @api.model
@@ -95,22 +96,77 @@ class PosOrder(models.Model):
 
         return new_session
 
+
     @api.model
-    def _process_order(self, pos_order):
-        pos_session = self.env['pos.session'].browse(pos_order['pos_session_id'])
+    def _process_order(self, order, draft, existing_order):
+        """Create or update an pos.order from a given dictionary.
+
+        :param pos_order: dictionary representing the order.
+        :type pos_order: dict.
+        :param draft: Indicate that the pos_order is not validated yet.
+        :type draft: bool.
+        :param existing_order: order to be updated or False.
+        :type existing_order: pos.order.
+        :returns number pos_order id
+        """
+        to_invoice = order['to_invoice'] if not draft else False
+        order = order['data']
+        pos_session = self.env['pos.session'].browse(order['pos_session_id'])
         if pos_session.state == 'closing_control' or pos_session.state == 'closed':
-            pos_order['pos_session_id'] = self._get_valid_session(pos_order).id
-        order = self.create(self._order_fields(pos_order))
+            order['pos_session_id'] = self._get_valid_session(order).id
+
+        pos_order = False
+        if not existing_order:
+            pos_order = self.create(self._order_fields(order))
+        else:
+            pos_order = existing_order
+            pos_order.lines.unlink()
+            order['user_id'] = pos_order.user_id.id
+            pos_order.write(self._order_fields(order))
+
+        self._process_payment_lines(order, pos_order, pos_session, draft)
+
+        if not draft:
+            try:
+                pos_order.action_pos_order_paid()
+            except psycopg2.DatabaseError:
+                # do not hide transactional errors, the order(s) won't be saved!
+                raise
+            except Exception as e:
+                _logger.error('Could not fully process the POS Order: %s', tools.ustr(e))
+
+        if to_invoice:
+            pos_order.action_pos_order_invoice()
+            pos_order.account_move.sudo().with_context(force_company=self.env.user.company_id.id).post()
+
+        return pos_order.id
+
+
+    def _process_payment_lines(self, pos_order, order, pos_session, draft):
+        """Create account.bank.statement.lines from the dictionary given to the parent function.
+
+        If the payment_line is an updated version of an existing one, the existing payment_line will first be
+        removed before making a new one.
+        :param pos_order: dictionary representing the order.
+        :type pos_order: dict.
+        :param order: Order object the payment lines should belong to.
+        :type order: pos.order
+        :param pos_session: PoS session the order was created in.
+        :type pos_session: pos.session
+        :param draft: Indicate that the pos_order is not validated yet.
+        :type draft: bool.
+        """
         prec_acc = order.pricelist_id.currency_id.decimal_places
+
+        order_bank_statement_lines= self.env['pos.payment'].search([('pos_order_id', '=', order.id)])
+        order_bank_statement_lines.unlink()
         for payments in pos_order['statement_ids']:
             if not float_is_zero(payments[2]['amount'], precision_digits=prec_acc):
                 order.add_payment(self._payment_fields(order, payments[2]))
 
-        if pos_session.sequence_number <= pos_order['sequence_number']:
-            pos_session.write({'sequence_number': pos_order['sequence_number'] + 1})
-            pos_session.refresh()
+        order.amount_paid = sum(order.payment_ids.mapped('amount'))
 
-        if not float_is_zero(pos_order['amount_return'], prec_acc):
+        if not draft and not float_is_zero(pos_order['amount_return'], prec_acc):
             cash_payment_method = pos_session.payment_method_ids.filtered('is_cash_count')[:1]
             if not cash_payment_method:
                 raise UserError(_("No cash statement found for this session. Unable to record returned cash."))
@@ -122,7 +178,6 @@ class PosOrder(models.Model):
                 'payment_method_id': cash_payment_method.id,
             }
             order.add_payment(return_payment_vals)
-        return order
 
     def _prepare_invoice_line(self, order_line):
         return {
@@ -195,18 +250,16 @@ class PosOrder(models.Model):
     )
     payment_ids = fields.One2many('pos.payment', 'pos_order_id', string='Payments', readonly=True)
     session_move_id = fields.Many2one('account.move', string='Session Journal Entry', related='session_id.move_id', readonly=True, copy=False)
+    to_invoice = fields.Boolean('To invoice')
     is_invoiced = fields.Boolean('Is Invoiced', compute='_compute_is_invoiced')
 
-    @api.depends('payment_ids', 'payment_ids.amount')
-    def _compute_amount_paid(self):
-        for order in self:
-            order.amount_paid = sum(order.payment_ids.mapped('amount'))
 
     @api.depends('account_move')
     def _compute_is_invoiced(self):
         for order in self:
             order.is_invoiced = bool(order.account_move)
 
+
     @api.depends('date_order', 'company_id', 'currency_id', 'company_id.currency_id')
     def _compute_currency_rate(self):
         for order in self:
@@ -343,34 +396,27 @@ class PosOrder(models.Model):
         return self.write({'state': 'cancel'})
 
     @api.model
-    def create_from_ui(self, orders):
-        # Keep only new orders
-        submitted_references = [o['data']['name'] for o in orders]
-        pos_order = self.search([('pos_reference', 'in', submitted_references)])
-        existing_orders = pos_order.read(['pos_reference'])
-        existing_references = set([o['pos_reference'] for o in existing_orders])
-        orders_to_save = [o for o in orders if o['data']['name'] not in existing_references]
+    def create_from_ui(self, orders, draft=False):
+        """ Create and update Orders from the frontend PoS application.
+
+        Create new orders and update orders that are in draft status. If an order already exists with a status
+        diferent from 'draft'it will be discareded, otherwise it will be saved to the database. If saved with
+        'draft' status the order can be overwritten later by this function.
+
+        :param orders: dictionary with the orders to be created.
+        :type orders: dict.
+        :param draft: Indicate if the orders are ment to be finalised or temporarily saved.
+        :type draft: bool.
+        :Returns: list -- list of db-ids for the created and updated orders.
+        """
         order_ids = []
+        for order in orders:
+            existing_order = False
+            if 'server_id' in order['data']:
+                existing_order = self.env['pos.order'].search([('id', '=', order['data']['server_id'])], limit=1)
+            order_ids.append(self._process_order(order, draft, existing_order))
 
-        for tmp_order in orders_to_save:
-            to_invoice = tmp_order['to_invoice']
-            order = tmp_order['data']
-
-            pos_order = self._process_order(order)
-            order_ids.append(pos_order.id)
-
-            try:
-                pos_order.action_pos_order_paid()
-            except psycopg2.DatabaseError:
-                # do not hide transactional errors, the order(s) won't be saved!
-                raise
-            except Exception as e:
-                _logger.error('Could not fully process the POS Order: %s', tools.ustr(e))
-
-            if to_invoice:
-                pos_order.action_pos_order_invoice()
-                pos_order.account_move.sudo().with_context(force_company=self.env.user.company_id.id).post()
-        return order_ids
+        return self.env['pos.order'].search_read(domain = [('id', 'in', order_ids)], fields = ['id', 'pos_reference'])
 
     def create_picking(self):
         """Create a picking for each order and validate it."""
@@ -516,7 +562,7 @@ class PosOrder(models.Model):
         """Create a new payment for the order"""
         self.ensure_one()
         self.env['pos.payment'].create(data)
-        self.amount_paid = sum(payment.amount for payment in self.payment_ids)
+        self.amount_paid = sum(self.payment_ids.mapped('amount'))
 
     def refund(self):
         """Create a copy of order  for refund order"""
@@ -558,6 +604,19 @@ class PosOrder(models.Model):
             'target': 'current',
         }
 
+    @api.model
+    def remove_from_ui(self, server_ids):
+        """ Remove orders from the frontend PoS application
+
+        Remove orders from the server by id.
+        :param server_ids: list of the id's of orders to remove from the server.
+        :type server_ids: list.
+        :returns: list -- list of db-ids for the removed orders.
+        """
+        orders = self.search([('id', 'in', server_ids),('state', '=', 'draft')])
+        orders.write({'state': 'cancel'})
+        orders.sudo().unlink()
+        return orders.ids
 
 class PosOrderLine(models.Model):
     _name = "pos.order.line"
@@ -642,6 +701,15 @@ class PosOrderLine(models.Model):
             values['name'] = self.env['ir.sequence'].next_by_code('pos.order.line')
         return super(PosOrderLine, self).create(values)
 
+    @api.model
+    def write(self, values):
+        if values.get('pack_lot_line_ids'):
+            for pl in values.get('pack_lot_ids'):
+                if pl[2].get('server_id'):
+                    pl[2]['id'] = pl[2]['server_id']
+                    del pl[2]['server_id']
+        return super().write(values)
+
     @api.onchange('price_unit', 'tax_ids', 'qty', 'discount', 'product_id')
     def _onchange_amount_line_all(self):
         for line in self:
diff --git a/addons/point_of_sale/models/pos_session.py b/addons/point_of_sale/models/pos_session.py
index 0f200cf971d..0ff8e78550b 100644
--- a/addons/point_of_sale/models/pos_session.py
+++ b/addons/point_of_sale/models/pos_session.py
@@ -153,16 +153,6 @@ class PosSession(models.Model):
                     session.cash_register_id = statement.id
                     break  # stop iteration after finding the cash journal
 
-    @api.constrains('user_id', 'state')
-    def _check_unicity(self):
-        # open if there is no session in 'opening_control', 'opened', 'closing_control' for one user
-        if self.search_count([
-                ('state', 'not in', ('closed', 'closing_control')),
-                ('user_id', '=', self.user_id.id),
-                ('rescue', '=', False)
-            ]) > 1:
-            raise ValidationError(_("You cannot create two active sessions with the same responsible."))
-
     @api.constrains('config_id')
     def _check_pos_config(self):
         if self.search_count([
@@ -754,15 +744,19 @@ class PosSession(models.Model):
         }
 
     def open_frontend_cb(self):
+        """Open the pos interface with config_id as an extra argument.
+            
+        In vanilla PoS each user can only have one active session, therefore it was not needed to pass the config_id
+        on opening a session. It is also possible to login to sessions created by other users.
+            
+        :returns: dict
+        """
         if not self.ids:
             return {}
-        for session in self.filtered(lambda s: s.user_id.id != self.env.uid):
-            raise UserError(_("You cannot use the session of another user. This session is owned by %s. "
-                              "Please first close this one to use this point of sale.") % session.user_id.name)
         return {
             'type': 'ir.actions.act_url',
             'target': 'self',
-            'url':   '/pos/web/',
+            'url':   '/pos/web?config_id=%d' % self.config_id.id,
         }
 
     def open_cashbox_pos(self):
diff --git a/addons/point_of_sale/static/src/js/chrome.js b/addons/point_of_sale/static/src/js/chrome.js
index 436b54cea1c..c148f8ed7b4 100644
--- a/addons/point_of_sale/static/src/js/chrome.js
+++ b/addons/point_of_sale/static/src/js/chrome.js
@@ -248,7 +248,7 @@ var DebugWidget = PosBaseWidget.extend({
                 'body':  _t('This operation will permanently destroy all paid orders from the local storage. You will lose all the data. This operation cannot be undone.'),
                 confirm: function(){
                     self.pos.db.remove_all_orders();
-                    self.pos.set({synch: { state:'connected', pending: 0 }});
+                    self.pos.set_synch('connected', 0);
                 },
             });
         });
diff --git a/addons/point_of_sale/static/src/js/db.js b/addons/point_of_sale/static/src/js/db.js
index 96083b0a247..cb4bd43b83f 100644
--- a/addons/point_of_sale/static/src/js/db.js
+++ b/addons/point_of_sale/static/src/js/db.js
@@ -488,6 +488,54 @@ var PosDB = core.Class.extend({
         }
         return orders;
     },
+    /**
+     * Return the orders with requested ids if they are unpaid.
+     * @param {array<number>} ids order_ids.
+     * @return {array<object>} list of orders.
+     */
+    get_unpaid_orders_to_sync: function(ids){
+        var saved = this.load('unpaid_orders',[]);
+        var orders = [];
+        saved.forEach(function(o) {
+            if (ids.includes(o.id) && (o.data.server_id || o.data.lines.length)){
+                orders.push(o);
+            }
+        });
+        return orders;
+    },
+    /**
+     * Add a given order to the orders to be removed from the server.
+     *
+     * If an order is removed from a table it also has to be removed from the server to prevent it from reapearing 
+     * after syncing. This function will add the server_id of the order to a list of orders still to be removed.
+     * @param {object} order object.
+     */
+    set_order_to_remove_from_server: function(order){
+        if (order.server_id !== undefined) {
+            var to_remove = this.load('unpaid_orders_to_remove',[]);
+            to_remove.push(order.server_id);
+            this.save('unpaid_orders_to_remove', to_remove);
+        }
+    },
+    /**
+     * Get a list of server_ids of orders to be removed.
+     * @return {array<number>} list of server_ids.
+     */
+    get_ids_to_remove_from_server: function(){
+        return this.load('unpaid_orders_to_remove',[]);
+    },
+    /**
+     * Remove server_ids from the list of orders to be removed.
+     * @param {array<number>} ids
+     */
+    set_ids_removed_from_server: function(ids){
+        var to_remove = this.load('unpaid_orders_to_remove',[]);
+        
+        to_remove = _.filter(to_remove, function(id){
+            return !ids.includes(id);
+        });
+        this.save('unpaid_orders_to_remove', to_remove);
+    },
     set_cashier: function(cashier) {
         // Always update if the user is the same as before
         this.save('cashier', cashier || null);
diff --git a/addons/point_of_sale/static/src/js/gui.js b/addons/point_of_sale/static/src/js/gui.js
index d50ad71faea..0253e4aece6 100644
--- a/addons/point_of_sale/static/src/js/gui.js
+++ b/addons/point_of_sale/static/src/js/gui.js
@@ -25,6 +25,7 @@ var Gui = core.Class.extend({
         this.startup_screen = null;
         this.current_popup  = null;
         this.current_screen = null;
+        this.show_sync_errors = true;
 
         this.chrome.ready.then(function(){
             self.close_other_tabs();
@@ -165,6 +166,15 @@ var Gui = core.Class.extend({
         this.current_popup = this.popup_instances[name];
         return this.current_popup.show(options);
     },
+    show_sync_error_popup: function() {
+        if (this.show_sync_errors) {
+            this.show_popup('error-sync',{
+                'title':_t('Changes could not be saved'),
+                'body': _t('You must be connected to the internet to save your changes.\n\n' +
+                        'Orders that where not synced before will be synced next time you close an order while connected to the internet or when you close the session.'),
+            });
+        }
+    },
 
     // close the current popup.
     close_popup: function() {
diff --git a/addons/point_of_sale/static/src/js/models.js b/addons/point_of_sale/static/src/js/models.js
index 7a3fa82e252..a2da7016a4a 100644
--- a/addons/point_of_sale/static/src/js/models.js
+++ b/addons/point_of_sale/static/src/js/models.js
@@ -67,6 +67,10 @@ exports.PosModel = Backbone.Model.extend({
         this.order_sequence = 1;
         window.posmodel = this;
 
+        // Extract the config id from the url.
+        var given_config = new RegExp('[\?&]config_id=([^&#]*)').exec(window.location.href);
+        this.config_id = given_config && given_config[1] && parseInt(given_config[1]) || false;
+
         // these dynamic attributes can be watched for change by other models or widgets
         this.set({
             'synch':            { state:'connected', pending:0 },
@@ -251,15 +255,23 @@ exports.PosModel = Backbone.Model.extend({
     },{
         model:  'pos.session',
         fields: ['id', 'name', 'user_id', 'config_id', 'start_at', 'stop_at', 'sequence_number', 'login_number', 'payment_method_ids'],
-        domain: function(self){ return [['state','=','opened'],['user_id','=',session.uid]]; },
-        loaded: function(self,pos_sessions,tmp){
+        domain: function(self){
+            var domain = [
+                ['state','=','opened'],
+                ['rescue', '=', false],
+            ];
+            if (self.config_id) domain.push(['config_id', '=', self.config_id]);
+            return domain;
+        },
+        loaded: function(self, pos_sessions, tmp){
             self.pos_session = pos_sessions[0];
+            self.config_id = self.config_id || self.pos_session && self.pos_session.config_id[0];
             tmp.payment_method_ids = pos_sessions[0].payment_method_ids;
         },
     },{
         model: 'pos.config',
         fields: [],
-        domain: function(self){ return [['id','=', self.pos_session.config_id[0]]]; },
+        domain: function(self){ return [['id','=', self.config_id]]; },
         loaded: function(self,configs){
             self.config = configs[0];
             self.config.use_proxy = self.config.iface_payment_terminal ||
@@ -860,6 +872,7 @@ exports.PosModel = Backbone.Model.extend({
                         transfer.then(function(order_server_id){
                             // generate the pdf and download it
                             if (order_server_id.length) {
+                                order_server_id[0] = order_server_id[0]["id"];
                                 self.chrome.do_action('point_of_sale.pos_invoice_report',{additional_context:{
                                     active_ids:order_server_id,
                                 }}).then(function () {
@@ -889,27 +902,24 @@ exports.PosModel = Backbone.Model.extend({
     // wrapper around the _save_to_server that updates the synch status widget
     _flush_orders: function(orders, options) {
         var self = this;
-        this.set('synch',{ state: 'connecting', pending: orders.length});
+        this.set_synch('connecting', orders.length);
 
-        return self._save_to_server(orders, options).then(function (server_ids) {
-            var pending = self.db.get_orders().length;
-
-            self.set('synch', {
-                state: pending ? 'connecting' : 'connected',
-                pending: pending
-            });
-
-            return server_ids;
+        return this._save_to_server(orders, options).then(function (server_ids) {
+            self.set_synch('connected');
+            return _.pluck(server_ids, 'id');
         }).catch(function(){
-            var pending = self.db.get_orders().length;
-            if (self.get('failed')) {
-                self.set('synch', { state: 'error', pending: pending });
-            } else {
-                self.set('synch', { state: 'disconnected', pending: pending });
-            }
+            self.set_synch(self.get('failed') ? 'error' : 'disconnected');
         });
     },
 
+    set_synch: function(state, pending) {
+        if (['connected', 'connecting', 'error', 'disconnected'].indexOf(state) === -1) {
+            console.error(state, ' is not a known connection state.');
+        }
+        pending = pending || this.db.get_orders().length + this.db.get_ids_to_remove_from_server().length;
+        this.set('synch', { state: state, pending: pending });
+    },
+
     // send an array of orders to the server
     // available options:
     // - timeout: timeout for the rpc call in ms
@@ -936,6 +946,7 @@ exports.PosModel = Backbone.Model.extend({
                 order.to_invoice = options.to_invoice || false;
                 return order;
             })];
+        args.push(options.draft || false);
         return rpc.query({
                 model: 'pos.order',
                 method: 'create_from_ui',
@@ -969,6 +980,49 @@ exports.PosModel = Backbone.Model.extend({
                     self.set('failed',error);
                 }
                 console.error('Failed to send orders:', orders);
+                self.gui.show_sync_error_popup();
+                throw reason;
+            });
+    },
+
+    /**
+     * Remove orders with given ids from the database.
+     * @param {array<number>} server_ids ids of the orders to be removed.
+     * @param {dict} options.
+     * @param {number} options.timeout optional timeout parameter for the rpc call.
+     * @return {Promise<array<number>>} returns a promise of the ids successfully removed.
+     */
+    _remove_from_server: function (server_ids, options) {
+        options = options || {};
+        if (!server_ids || !server_ids.length) {
+            return Promise.resolve([]);
+        }
+
+        var self = this;
+        var timeout = typeof options.timeout === 'number' ? options.timeout : 7500 * server_ids.length;
+
+        return rpc.query({
+                model: 'pos.order',
+                method: 'remove_from_ui',
+                args: [server_ids],
+                kwargs: {context: session.user_context},
+            }, {
+                timeout: timeout,
+                shadow: true,
+            })
+            .then(function (ids) {
+                self.db.set_ids_removed_from_server(server_ids);
+                return server_ids;
+            }).catch(function (reason){
+                var error = reason.message;
+                if(error.code === 200 ){    // Business Logic Error, not a connection problem
+                    //if warning do not need to display traceback!!
+                    if (error.data.exception_type == 'warning') {
+                        delete error.data.debug;
+                    }
+                }
+                self.gui.show_sync_error_popup();
+                console.error('Failed to remove orders:', server_ids);
             });
     },
 
@@ -1334,7 +1388,7 @@ exports.Orderline = Backbone.Model.extend({
         this.price = json.price_unit;
         this.set_discount(json.discount);
         this.set_quantity(json.qty, 'do not recompute unit price');
-        this.id    = json.id;
+        this.id = json.id ? json.id : orderline_id++;
         orderline_id = Math.max(this.id+1,orderline_id);
         var pack_lot_lines = json.pack_lot_ids;
         for (var i = 0; i < pack_lot_lines.length; i++) {
@@ -2152,6 +2206,8 @@ exports.Order = Backbone.Model.extend({
         this.uid = json.uid;
         this.name = _t("Order ") + this.uid;
         this.validation_date = json.creation_date;
+        this.server_id = json.server_id ? json.server_id : false;
+        this.user_id = json.user_id;
 
         if (json.fiscal_position_id) {
             var fiscal_position = _.find(this.pos.fiscal_positions, function (fp) {
@@ -2213,7 +2269,7 @@ exports.Order = Backbone.Model.extend({
         this.paymentlines.each(_.bind( function(item) {
             return paymentLines.push([0, 0, item.export_as_JSON()]);
         }, this));
-        return {
+        var json = {
             name: this.get_name(),
             amount_paid: this.get_total_paid() - this.get_change(),
             amount_total: this.get_total_with_tax(),
@@ -2229,8 +2285,13 @@ exports.Order = Backbone.Model.extend({
             uid: this.uid,
             sequence_number: this.sequence_number,
             creation_date: this.validation_date || this.creation_date, // todo: rename creation_date in master
-            fiscal_position_id: this.fiscal_position ? this.fiscal_position.id : false
+            fiscal_position_id: this.fiscal_position ? this.fiscal_position.id : false,
+            server_id: this.server_id ? this.server_id : false,
         };
+        if (!this.is_paid && this.user_id) {
+            json.user_id = this.user_id;
+        }
+        return json;
     },
     export_for_printing: function(){
         var orderlines = [];
diff --git a/addons/point_of_sale/static/src/js/popups.js b/addons/point_of_sale/static/src/js/popups.js
index e27ffc75dd6..89d9b8d6a7e 100644
--- a/addons/point_of_sale/static/src/js/popups.js
+++ b/addons/point_of_sale/static/src/js/popups.js
@@ -98,6 +98,21 @@ var ErrorPopupWidget = PopupWidget.extend({
 gui.define_popup({name:'error', widget: ErrorPopupWidget});
 
 
+var SyncErrorPopupWidget = ErrorPopupWidget.extend({
+    template:'SyncErrorPopupWidget',
+    show: function(opts) {
+        var self = this;
+        this._super(opts);
+
+        this.$('.stop_showing_sync_errors').off('click').click(function(){
+            self.gui.show_sync_errors = false;
+            self.click_confirm();
+        });
+    }
+});
+gui.define_popup({name:'error-sync', widget: SyncErrorPopupWidget});
+
+
 var ErrorTracebackPopupWidget = ErrorPopupWidget.extend({
     template:'ErrorTracebackPopupWidget',
     show: function(opts) {
diff --git a/addons/point_of_sale/static/src/xml/pos.xml b/addons/point_of_sale/static/src/xml/pos.xml
index 3d4c2462b94..26fe124b55e 100644
--- a/addons/point_of_sale/static/src/xml/pos.xml
+++ b/addons/point_of_sale/static/src/xml/pos.xml
@@ -1052,6 +1052,23 @@
         </div>
     </t>
 
+    <t t-name="SyncErrorPopupWidget">
+        <div role="dialog" class="modal-dialog">
+            <div class="popup popup-error">
+                <header class="title"><t t-esc=" widget.options.title || 'Error' " /></header>
+                <main class="body traceback"><t t-esc=" widget.options.body || '' "/></main>
+                <footer class="footer">
+                    <div class="button cancel">
+                        Ok
+                    </div>
+                    <div class="button stop_showing_sync_errors">
+                        Don't show again
+                    </div>
+                </footer>
+            </div>
+        </div>
+    </t>
+
     <t t-name="ErrorTracebackPopupWidget">
         <div role="dialog" class="modal-dialog">
             <div class="popup popup-error">
@@ -1469,15 +1486,14 @@
                     <t t-if='order === widget.pos.get_order()'>
                         <span class="order-button select-order selected" t-att-data-uid="order.uid">
                             <span class='order-sequence'>
-                                <t t-esc='order.sequence_number' />
+                                <t t-esc="order.uid.substring(order.uid.indexOf('-') +1)"/>
                             </span>
-                            <t t-esc="moment(order.creation_date).format('hh:mm')"/>
                         </span>
                     </t>
                     <t t-if='order !== widget.pos.get_order()'>
                         <span class="order-button select-order" t-att-data-uid="order.uid">
                             <span class='order-sequence'>
-                                <t t-esc='order.sequence_number' />
+                                <t t-esc="order.uid.substring(order.uid.indexOf('-') +1)"/>
                             </span>
                         </span>
                     </t>
diff --git a/addons/point_of_sale/static/tests/tours/point_of_sale.js b/addons/point_of_sale/static/tests/tours/point_of_sale.js
index 71cbeef006b..352624a61c3 100644
--- a/addons/point_of_sale/static/tests/tours/point_of_sale.js
+++ b/addons/point_of_sale/static/tests/tours/point_of_sale.js
@@ -45,10 +45,6 @@ odoo.define('point_of_sale.tour.pricelist', function (require) {
     }
 
     var steps = [{ // Leave category displayed by default
-        content: "click category switch",
-        trigger: ".js-category-switch",
-        run: 'click',
-    }, {
         content: 'waiting for loading to finish',
         trigger: 'body:has(.loader:hidden)',
         run: function () {
@@ -95,6 +91,10 @@ odoo.define('point_of_sale.tour.pricelist', function (require) {
         content: "wait for unit tests to finish",
         trigger: ".pos.done-testing",
         run: function () {}, // it's a check
+    }, {
+        content: "click category switch",
+        trigger: ".js-category-switch",
+        run: 'click',
     }, {
         content: "click pricelist button",
         trigger: ".control-button.o_pricelist_button",
diff --git a/addons/point_of_sale/tests/test_frontend.py b/addons/point_of_sale/tests/test_frontend.py
index 593c88876dc..772741a188d 100644
--- a/addons/point_of_sale/tests/test_frontend.py
+++ b/addons/point_of_sale/tests/test_frontend.py
@@ -323,9 +323,9 @@ class TestUi(odoo.tests.HttpCase):
         # this you end up with js, css but no qweb.
         env['ir.module.module'].search([('name', '=', 'point_of_sale')], limit=1).state = 'installed'
 
-        self.start_tour("/pos/web", 'pos_pricelist', login="admin")
+        self.start_tour("/pos/web?config_id=%d" % main_pos_config.id, 'pos_pricelist', login="admin")
 
-        self.start_tour("/pos/web", 'pos_basic_order', login="admin")
+        self.start_tour("/pos/web?config_id=%d" % main_pos_config.id, 'pos_basic_order', login="admin")
 
         for order in env['pos.order'].search([]):
             self.assertEqual(order.state, 'paid', "Validated order has payment of " + str(order.amount_paid) + " and total of " + str(order.amount_total))
diff --git a/addons/point_of_sale/tests/test_point_of_sale_flow.py b/addons/point_of_sale/tests/test_point_of_sale_flow.py
index 3466b4ca112..b42b8129cfe 100644
--- a/addons/point_of_sale/tests/test_point_of_sale_flow.py
+++ b/addons/point_of_sale/tests/test_point_of_sale_flow.py
@@ -540,10 +540,6 @@ class TestPointOfSaleFlow(TestPointOfSaleCommon):
         self.PosOrder.create_from_ui([carrot_order])
         self.assertEqual(num_starting_orders + 1, len(current_session.order_ids), "Submitted order not encoded")
 
-        # I resubmit the same order
-        self.PosOrder.create_from_ui([carrot_order])
-        self.assertEqual(num_starting_orders + 1, len(current_session.order_ids), "Resubmitted order was not skipped")
-
         # I close the session
         current_session.action_pos_session_closing_control()
         self.assertEqual(current_session.state, 'closed', "Session was not properly closed")
diff --git a/addons/point_of_sale/views/point_of_sale_dashboard.xml b/addons/point_of_sale/views/point_of_sale_dashboard.xml
index 00327b9daba..7a5fe9ab3dc 100644
--- a/addons/point_of_sale/views/point_of_sale_dashboard.xml
+++ b/addons/point_of_sale/views/point_of_sale_dashboard.xml
@@ -63,6 +63,9 @@
                                     <t t-if="record.pos_session_state.raw_value == 'new_session'">
                                         <div class="badge badge-info o_kanban_inline_block">New session</div>
                                     </t>
+                                    <t t-if="!record.current_session_id.raw_value &amp;&amp; record.pos_session_username.value">
+                                        <div class="badge badge-info o_kanban_inline_block">Opened by <t t-esc="record.pos_session_username.value"/></div>
+                                    </t>
                                     <t t-if="record.pos_session_state.raw_value == 'opening_control'">
                                         <div class="badge badge-info o_kanban_inline_block">Opening Control</div>
                                     </t>
diff --git a/addons/pos_hr/static/src/js/screens.js b/addons/pos_hr/static/src/js/screens.js
index 425bec4d78b..402bcbd7496 100644
--- a/addons/pos_hr/static/src/js/screens.js
+++ b/addons/pos_hr/static/src/js/screens.js
@@ -92,7 +92,7 @@ var LoginScreenWidget = ScreenWidget.extend({
     },
 
     unlock_screen: function() {
-        var screen = (this.gui.pos.get_order() ? this.gui.pos.get_order().get_screen_data('previous-screen') : this.gui.default_screen) || this.gui.default_screen;
+        var screen = (this.gui.pos.get_order() ? this.gui.pos.get_order().get_screen_data('previous-screen') : this.gui.startup_screen) || this.gui.startup_screen;
         this.gui.show_screen(screen);
     }
 });
diff --git a/addons/pos_restaurant/models/pos_config.py b/addons/pos_restaurant/models/pos_config.py
index 07c2dd88253..0dfe375ed9b 100644
--- a/addons/pos_restaurant/models/pos_config.py
+++ b/addons/pos_restaurant/models/pos_config.py
@@ -42,3 +42,11 @@ class PosConfig(models.Model):
     def _onchange_is_order_printer(self):
         if not self.is_order_printer:
             self.printer_ids = [(5, 0, 0)]
+
+    def get_tables_order_count(self):
+        """         """
+        self.ensure_one()
+        result = []
+        for table in self.floor_ids.table_ids.filtered(lambda t: t.active ==  True):
+            result.append({'id': table.id, 'orders': self.env['pos.order'].search_count([('state', '=', 'draft'), ('table_id', '=', table.id)])})
+        return result
diff --git a/addons/pos_restaurant/models/pos_order.py b/addons/pos_restaurant/models/pos_order.py
index fa6ba65eec5..50220379b1a 100644
--- a/addons/pos_restaurant/models/pos_order.py
+++ b/addons/pos_restaurant/models/pos_order.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 # Part of Odoo. See LICENSE file for full copyright and licensing details.
+from itertools import groupby
 
 from odoo import api, fields, models
 
@@ -17,6 +18,153 @@ class PosOrder(models.Model):
     table_id = fields.Many2one('restaurant.table', string='Table', help='The table where this order was served')
     customer_count = fields.Integer(string='Guests', help='The amount of customers that have been served by this order.')
 
+    def _get_pack_lot_lines(self, order_lines):
+        """Add pack_lot_lines to the order_lines.
+
+        The function doesn't return anything but adds the results directly to the order_lines.
+
+        :param order_lines: order_lines for which the pack_lot_lines are to be requested.
+        :type order_lines: pos.order.line.
+        """
+        pack_lots = self.env['pos.pack.operation.lot'].search_read(
+                domain = [('pos_order_line_id', 'in', [order_line['id'] for order_line in order_lines])],
+                fields = [
+                    'id',
+                    'lot_name',
+                    'pos_order_line_id'
+                    ])
+        for pack_lot in pack_lots:
+            pack_lot['order_line'] = pack_lot['pos_order_line_id'][0]
+            pack_lot['server_id'] = pack_lot['id']
+
+            del pack_lot['pos_order_line_id']
+            del pack_lot['id']
+
+        for order_line_id, pack_lot_ids in groupby(pack_lots, key=lambda x:x['order_line']):
+            next(order_line for order_line in order_lines if order_line['id'] == order_line_id)['pack_lot_ids'] = list(pack_lots)
+
+    def _get_order_lines(self, orders):
+        """Add pos_order_lines to the orders.
+
+        The function doesn't return anything but adds the results directly to the orders.
+
+        :param orders: orders for which the order_lines are to be requested.
+        :type orders: pos.order.
+        """
+        order_lines = self.env['pos.order.line'].search_read(
+                domain = [('order_id', 'in', [to['id'] for to in orders])],
+                fields = [
+                    'id',
+                    'discount',
+                    'product_id',
+                    'price_unit',
+                    'order_id',
+                    'qty',
+                    'note',
+                    'mp_skip',
+                    ])
+
+        if order_lines != []:
+            self._get_pack_lot_lines(order_lines)
+
+        extended_order_lines = []
+        for order_line in order_lines:
+            order_line['product_id'] = order_line['product_id'][0]
+            order_line['server_id'] = order_line['id']
+
+            del order_line['id']
+            if not 'pack_lot_ids' in order_line:
+                order_line['pack_lot_ids'] = []
+            extended_order_lines.append([0, 0, order_line])
+
+        for order_id, order_lines in groupby(extended_order_lines, key=lambda x:x[2]['order_id']):
+            next(order for order in orders if order['id'] == order_id[0])['lines'] = list(order_lines)
+
+    def _get_payment_lines(self, orders):
+        """Add account_bank_statement_lines to the orders.
+
+        The function doesn't return anything but adds the results directly to the orders.
+
+        :param orders: orders for which the payment_lines are to be requested.
+        :type orders: pos.order.
+        """
+        payment_lines = self.env['pos.payment'].search_read(
+                domain = [('pos_order_id', 'in', [po['id'] for po in orders])],
+                fields = [
+                    'id',
+                    'amount',
+                    'pos_order_id',
+                    'payment_method_id',
+                    ])
+
+        extended_payment_lines = []
+        for payment_line in payment_lines:
+            payment_line['server_id'] = payment_line['id']
+            payment_line['payment_method_id'] = payment_line['payment_method_id'][0]
+
+            del payment_line['id']
+            extended_payment_lines.append([0, 0, payment_line])
+        for order_id, payment_lines in groupby(extended_payment_lines, key=lambda x:x[2]['pos_order_id']):
+            next(order for order in orders if order['id'] == order_id[0])['statement_ids'] = list(payment_lines)
+
+    @api.model
+    def get_table_draft_orders(self, table_id):
+        """Generate an object of all draft orders for the given table.
+
+        Generate and return an JSON object with all draft orders for the given table, to send to the 
+        front end application.
+
+        :param table_id: Id of the selected table.
+        :type table_id: int.
+        :returns: list -- list of dict representing the table orders
+        """
+        table_orders = self.search_read(
+                domain = [('state', '=', 'draft'), ('table_id', '=', table_id)],
+                fields = [
+                    'id',
+                    'pricelist_id',
+                    'partner_id',
+                    'sequence_number',
+                    'session_id',
+                    'pos_reference',
+                    'create_uid',
+                    'create_date',
+                    'customer_count',
+                    'fiscal_position_id',
+                    'table_id',
+                    'to_invoice',
+                    ])
+
+        self._get_order_lines(table_orders)
+        self._get_payment_lines(table_orders)
+
+        for order in table_orders:
+            order['pos_session_id'] = order['session_id']
+            order['uid'] = order['pos_reference'].split(' ')[1]
+            order['name'] = order['pos_reference']
+            order['creation_date'] = order['create_date']
+            order['server_id'] = order['id']
+            if order['fiscal_position_id']:
+                order['fiscal_position_id'] = order['fiscal_position_id'][0]
+            if order['pricelist_id']:
+                order['pricelist_id'] = order['pricelist_id'][0]
+            if order['partner_id']:
+                order['partner_id'] = order['partner_id'][0]
+            if order['table_id']:
+                order['table_id'] = order['table_id'][0]
+
+            if not 'lines' in order:
+                order['lines'] = []
+            if not 'statement_ids' in order:
+                order['statement_ids'] = []
+
+            del order['id']
+            del order['session_id']
+            del order['pos_reference']
+            del order['create_date']
+
+        return table_orders
+
     @api.model
     def _order_fields(self, ui_order):
         order_fields = super(PosOrder, self)._order_fields(ui_order)
diff --git a/addons/pos_restaurant/static/src/js/floors.js b/addons/pos_restaurant/static/src/js/floors.js
index ba75ef52366..847c9b2f22d 100644
--- a/addons/pos_restaurant/static/src/js/floors.js
+++ b/addons/pos_restaurant/static/src/js/floors.js
@@ -8,6 +8,7 @@ var models = require('point_of_sale.models');
 var screens = require('point_of_sale.screens');
 var core = require('web.core');
 var rpc = require('web.rpc');
+var session = require('web.session');
 
 var QWeb = core.qweb;
 var _t = core._t;
@@ -218,10 +219,7 @@ var TableWidget = PosBaseWidget.extend({
                         self.renderElement();
                     });
             }, function(type,err) {
-                self.gui.show_popup('error',{
-                    'title':_t('Changes could not be saved'),
-                    'body': _t('You must be connected to the internet to save your changes.'),
-                });
+                    self.gui.show_sync_error_popup();
             });
     },
     // destroy the table.  We do not really destroy it, we set it
@@ -257,10 +255,7 @@ var TableWidget = PosBaseWidget.extend({
                 floorplan.update_toolbar();
                 self.destroy();
             }, function(type, err) {
-                self.gui.show_popup('error', {
-                    'title':_t('Changes could not be saved'),
-                    'body': _t('You must be connected to the internet to save your changes.'),
-                });
+                self.gui.show_sync_error_popup();
             });
     },
     get_notifications: function(){  //FIXME : Make this faster
@@ -276,19 +271,22 @@ var TableWidget = PosBaseWidget.extend({
         }
         return notifications;
     },
-        update_click_handlers: function(editing){
-            var self = this;
-            this.$el.off('mouseup touchend touchcancel click dragend');
+    update_click_handlers: function(editing){
+        var self = this;
+        this.$el.off('mouseup touchend touchcancel click dragend');
 
-            if (editing) {
-                this.$el.on('mouseup touchend touchcancel', function(event){ self.click_handler(event,$(this)); });
-            } else {
-                this.$el.on('click dragend', function(event){ self.click_handler(event,$(this)); });
-            }
-        },
+        if (editing) {
+            this.$el.on('mouseup touchend touchcancel', function(event){ self.click_handler(event,$(this)); });
+        } else {
+            this.$el.on('click dragend', function(event){ self.click_handler(event,$(this)); });
+        }
+    },
     renderElement: function(){
         var self = this;
-        this.order_count    = this.pos.get_table_orders(this.table).length;
+        this.order_count    = this.table.order_count !== undefined ?
+            this.table.order_count :
+            this.pos.get_table_orders(this.table)
+                .filter(o => o.orderlines.length !== 0 || o.paymentlines.length !==0).length;
         this.customer_count = this.pos.get_customer_count(this.table);
         this.fill           = Math.min(1,Math.max(0,this.customer_count / this.table.seats));
         this.notifications  = this.get_notifications();
@@ -315,12 +313,41 @@ var FloorScreenWidget = screens.ScreenWidget.extend({
         this.selected_table = null;
         this.editing = false;
     },
+    _table_longpolling: function(){
+        var self = this;
+        rpc.query({
+            model: 'pos.config',
+            method: 'get_tables_order_count',
+            args: [this.pos.config.id],
+        })
+        .then(function (result){
+            result.forEach(function(table){
+                var table_obj = self.pos.tables_by_id[table.id];
+                var unsynced_orders = self.pos.get_table_orders(table_obj)
+                    .filter(o => o.server_id === undefined &&
+                            (o.orderlines.length !== 0 || o.paymentlines.length !== 0)).length
+                table_obj.order_count = table.orders + unsynced_orders;
+            });
+            self.table_widgets.forEach(
+                    function(tw){
+                        tw.renderElement();
+                    });
+        }, function(type,err) {
+            self.table_widgets.forEach(
+                    function(tw){
+                        tw.table.order_count = self.pos.get_table_orders(tw.table)
+                            .filter(o => o.orderlines.length !== 0 || o.paymentlines.length !== 0).length
+                        tw.renderElement();
+                    });
+        });
+    },
     hide: function(){
         this._super();
         if (this.editing) {
             this.toggle_editing();
         }
         this.chrome.widget.order_selector.show();
+        clearInterval(this.table_longpolling);
     },
     show: function(){
         this._super();
@@ -329,6 +356,9 @@ var FloorScreenWidget = screens.ScreenWidget.extend({
             this.table_widgets[i].renderElement();
         }
         this.check_empty_floor();
+
+        this._table_longpolling();
+        this.table_longpolling = setInterval(this._table_longpolling.bind(this), 5000);
     },
     click_floor_button: function(event,$el){
         var floor = this.pos.floors_by_id[$el.data('id')];
@@ -364,10 +394,7 @@ var FloorScreenWidget = screens.ScreenWidget.extend({
                 args: [[this.floor.id], {'background_color': background}],
             })
             .guardedCatch(function (){
-                self.gui.show_popup('error',{
-                    'title':_t('Changes could not be saved'),
-                    'body': _t('You must be connected to the internet to save your changes.'),
-                });
+                self.gui.show_sync_error_popup();
             });
         this.$('.floor-map').css({"background-color": _.escape(background)});
     },
@@ -662,6 +689,19 @@ gui.define_screen({
     },
 });
 
+gui.Gui.include({
+    show_sync_error_popup: function() {
+        if (this.show_sync_errors) {
+            this.show_popup('error-sync',{
+                'title':_t('Changes could not be saved'),
+                'body': _t('You must be connected to the internet to save your changes.\n\n' +
+                        'Changes made to previously synced orders will get lost at the next sync.\n' +
+                        'Orders that where not synced before will be synced next time you open and close the same table.'),
+            });
+        }
+    },
+});
+
 // Add the FloorScreen to the GUI, and set it as the default screen
 chrome.Chrome.include({
     build_widgets: function(){
@@ -753,9 +793,18 @@ chrome.OrderSelectorWidget.include({
 // if there is none.
 var _super_posmodel = models.PosModel.prototype;
 models.PosModel = models.PosModel.extend({
-    initialize: function(session, attributes) {
-        this.table = null;
-        return _super_posmodel.initialize.call(this,session,attributes);
+    after_load_server_data: function() {
+        _super_posmodel.after_load_server_data.call(this);
+        if (this.config.iface_floorplan) {
+	    var self = this;
+            this.table = null;
+	    $('.screen').not('.floor-screen').onmousemove = 	function() {self.set_idle_timer()};
+	    $('.screen').not('.floor-screen').onmousedown = 	function() {self.set_idle_timer()}; // touchscreen presses
+	    $('.screen').not('.floor-screen').ontouchstart = function() {self.set_idle_timer()};
+	    $('.screen').not('.floor-screen').onclick = 	function() {self.set_idle_timer()};     // touchpad clicks
+	    $('.screen').not('.floor-screen').onscroll = 	function() {self.set_idle_timer()};    // scrolling with arrow keys
+	    $('.screen').not('.floor-screen').onkeypress = 	function() {self.set_idle_timer()};
+        }
     },
 
     transfer_order_to_different_table: function () {
@@ -767,26 +816,154 @@ models.PosModel = models.PosModel.extend({
         this.set_table(null);
     },
 
-    // changes the current table.
-    set_table: function(table) {
-        if (!table) { // no table ? go back to the floor plan, see ScreenSelector
-            this.set_order(null);
-        } else if (this.order_to_transfer_to_different_table) {
-            this.order_to_transfer_to_different_table.table = table;
-            this.order_to_transfer_to_different_table.save_to_db();
-            this.order_to_transfer_to_different_table = null;
+    remove_from_server_and_set_sync_state: function(ids_to_remove){
+        var self = this;
+        this.set_synch('connecting', ids_to_remove.length);
+        self._remove_from_server(ids_to_remove)
+            .then(function(server_ids) {
+                self.set_synch('connected');
+            }).catch(function(reason){
+                self.set_synch('error');
+            });
+    },
 
-            // set this table
-            this.set_table(table);
+    /**
+     * Request the orders of the table with given id.
+     * @param {number} table_id.
+     * @param {dict} options.
+     * @param {number} options.timeout optional timeout parameter for the rpc call.
+     * @return {Promise}
+     */
+    _get_from_server: function (table_id, options) {
+        options = options || {};
+        var self = this;
+        var timeout = typeof options.timeout === 'number' ? options.timeout : 7500;
+        return rpc.query({
+                model: 'pos.order',
+                method: 'get_table_draft_orders',
+                args: [table_id],
+                kwargs: {context: session.user_context},
+            }, {
+                timeout: timeout,
+                shadow: false,
+            })
+    },
+
+    /**
+     * Set or unset a timeout to go back to the floorplan.
+     *
+     * if deactivate is true unset the timeout, Else set a timeout to go back to the floorplan and
+     * force a sync of the current table.
+     * @param {bool} deactivate optional boolean, default false.
+     * @param {number} timeout, optional timeout in miliseconds, default one minute.
+     */
+    set_idle_timer: function(deactivate, timeout) {
+        timeout = timeout || 60000;
+        deactivate = deactivate || false;
+        if (this.idle_timer) {
+            clearTimeout(this.idle_timer);
+        }
+        var self = this;
+        if (deactivate) {
+            clearTimeout(this.idle_timer);
+        } else {
+            this.idle_timer = setTimeout(function(){self.set_table(null)}, timeout);
+        }
+    },
+
+    /**
+     * Changes the current table.
+     *
+     * Switch table and make sure all nececery syncing tasks are done.
+     * @param {object} table.
+     */
+    set_table: function(table) {
+        var self = this;
+        var ids_to_remove = this.db.get_ids_to_remove_from_server();
+        if (!table || this.order_to_transfer_to_different_table) { // no table ? go back to the floor plan, see ScreenSelector
+            this.set_idle_timer(true);
+            var order_ids = [];
+            var table_orders = this.get_order_list();
+            table_orders.forEach(function(o){
+                order_ids.push(o.uid);
+            });
+
+            if (this.order_to_transfer_to_different_table && table) {
+                this.order_to_transfer_to_different_table.table = table;
+                this.order_to_transfer_to_different_table.save_to_db();
+                order_ids.push(this.order_to_transfer_to_different_table.uid);
+                table_orders.push(this.order_to_transfer_to_different_table);
+            }
+
+            var orders_to_sync = this.db.get_unpaid_orders_to_sync(order_ids);
+            if (orders_to_sync.length) {
+                this.set_synch('connecting', orders_to_sync.length);
+                this._save_to_server(orders_to_sync, {'draft': true})
+                    .then(function (server_ids) {
+                        server_ids.forEach(function(server_id){
+                            table_orders.some(function(o){
+                                if (o.name === server_id.pos_reference) {
+                                    o.server_id = server_id.id;
+                                    o.save_to_db();
+                                }
+                            });
+                        });
+                        if (!ids_to_remove.length) {
+                            self.set_synch('connected');
+                        } else {
+                            self.remove_from_server_and_set_sync_state(ids_to_remove);
+                        }
+                    }).catch(function(reason){
+                        self.set_synch('error');
+                    }).finally(function(){
+                        if (self.order_to_transfer_to_different_table && table) {
+                            self.order_to_transfer_to_different_table = null;
+                            self.set_table(table);
+                        }
+                    });
+            } else if (ids_to_remove.length) {
+                self.remove_from_server_and_set_sync_state(ids_to_remove);
+            }
+            this.set_order(null); // unset curent selected order
 
         } else {
+
+            clearInterval(this.table_longpolling);
             this.table = table;
-            var orders = this.get_order_list();
-            if (orders.length) {
-                this.set_order(orders[0]); // and go to the first one ...
-            } else {
-                this.add_new_order();  // or create a new order with the current table
-            }
+            this.set_idle_timer();
+
+            this.set_synch('connecting', 1);
+            this._get_from_server(table.id)
+                .then(function (server_orders) {
+                    var orders = self.get_order_list();
+                    orders.forEach(function(order){
+                        if (order.server_id){
+                            self.get("orders").remove(order);
+                            order.destroy();
+                        }
+                    });
+                    server_orders.forEach(function(server_order){
+                        if (server_order.lines.length){
+                            var new_order = new models.Order({},{pos: self, json: server_order});
+                            self.get("orders").add(new_order);
+                            new_order.save_to_db();
+                        }
+                    })
+                    if (!ids_to_remove.length) {
+                        self.set_synch('connected');
+                    } else {
+                        self.remove_from_server_and_set_sync_state(ids_to_remove);
+                    }
+                }).catch(function(reason){
+                    self.set_synch('error');
+                }).finally(function(){
+                    var orders = self.get_order_list();
+                    if (orders.length) {
+                        self.set_order(orders[0]); // and go to the first one ...
+                    } else {
+                        self.add_new_order();  // or create a new order with the current table
+                    }
+                });
         }
     },
 
@@ -860,6 +1037,9 @@ models.PosModel = models.PosModel.extend({
     on_removed_order: function(removed_order,index,reason){
         if (this.config.iface_floorplan) {
             var order_list = this.get_order_list();
+            if (reason === 'abandon') {
+                this.db.set_order_to_remove_from_server(removed_order);
+            }
             if( (reason === 'abandon' || removed_order.temporary) && order_list.length > 0){
                 this.set_order(order_list[index] || order_list[order_list.length -1]);
             }else{
diff --git a/addons/pos_restaurant/static/src/js/tours/pos_restaurant.js b/addons/pos_restaurant/static/src/js/tours/pos_restaurant.js
new file mode 100644
index 00000000000..b0f8a23f05b
--- /dev/null
+++ b/addons/pos_restaurant/static/src/js/tours/pos_restaurant.js
@@ -0,0 +1,228 @@
+odoo.define('pos_reataurant.tour.synchronized_table_management', function (require) {
+    "use strict";
+
+    var Tour = require("web_tour.tour");
+
+    function verify_order_total(total_str) {
+        return [{
+            content: 'order total contains ' + total_str,
+            trigger: '.order .total .value:contains("' + total_str + '")',
+            run: function () {}, // it's a check
+        }];
+    }
+
+    function verify_sync() {
+        return [{
+            content: "verify that the order is being sent to the backend",
+            trigger: ".js_connecting:visible",
+            run: function () {}, // it's a check
+        }, {
+            content: "verify that the order has been succesfully sent to the backend",
+            trigger: ".js_connected:visible",
+            run: function () {}, // it's a check
+        }];
+    }
+
+    function verify_orders_synced(order_count) {
+        return [{
+            content: "check synced",
+            trigger: ".order-sequence",
+            run: function() {
+                var orders = $('.order-sequence');
+                if (orders.length === order_count) {
+                    var fail = orders.toArray().some(function(order){
+                        return !order.firstChild.data.includes('S-');
+                    });
+                    if (fail) {
+                        throw "sync failed";
+                    }
+                } else {
+                    throw "sync failed";
+                }
+            },
+        }];
+    }
+
+    function add_product_to_order(product_name) {
+        return [{
+            content: 'buy ' + product_name,
+            trigger: '.product-list .product-name:contains("' + product_name + '")',
+        }, {
+            content: 'the ' + product_name + ' have been added to the order',
+            trigger: '.order .product-name:contains("' + product_name + '")',
+            run: function () {}, // it's a check
+        }];
+    }
+
+    function generate_keypad_steps(amount_str, keypad_selector) {
+        var i, steps = [], current_char;
+        for (i = 0; i < amount_str.length; ++i) {
+            current_char = amount_str[i];
+            steps.push({
+                content: 'press ' + current_char + ' on payment keypad',
+                trigger: keypad_selector + ' .input-button:contains("' + current_char + '"):visible'
+            });
+        }
+
+        return steps;
+    }
+
+    function generate_payment_screen_keypad_steps(amount_str) {
+        return generate_keypad_steps(amount_str, '.payment-numpad');
+    }
+
+    function generate_product_screen_keypad_steps(amount_str) {
+        return generate_keypad_steps(amount_str, '.numpad');
+    }
+
+    function goto_payment_screen_and_select_payment_method() {
+        return [{
+            content: "go to payment screen",
+            trigger: '.button.pay',
+        }, {
+            content: "pay with cash",
+            trigger: '.paymentmethod:contains("Cash")',
+        }];
+    }
+
+    function open_table(table_id, order_count) {
+        order_count = order_count || null;
+        var steps = [{
+            content: 'open table ' + table_id,
+            trigger: '.label:contains(' + table_id +')',
+            run: 'click',
+        }];
+        steps = steps.concat(verify_sync());
+        if (order_count !== null){
+            steps = steps.concat(verify_orders_synced(order_count));
+        }
+        return steps;
+    }
+
+    function finish_order() {
+        var steps = [{
+            content: "validate the order",
+            trigger: '.button.next:visible',
+        }];
+        steps = steps.concat(verify_sync());
+        steps = steps.concat([{
+            content: "next order",
+            trigger: '.button.next:visible',
+        }]);
+        return steps;
+    }
+
+    /* pos_restaurant_sync
+     *
+     * Run on new session.
+     */
+    var steps = [{
+        content: 'waiting for loading to finish',
+        trigger: 'body:has(.loader:hidden)',
+        run: function () {},
+    }]
+
+
+    steps = steps.concat(open_table('T5'));
+
+    steps = steps.concat(add_product_to_order('Coca-Cola'));
+    steps = steps.concat(add_product_to_order('Water'));
+    steps = steps.concat(verify_order_total('4.40'));
+    steps = steps.concat([{
+        content: 'start new order',
+        trigger: '.neworder-button',
+        run: 'click',
+    }]);
+    steps = steps.concat(add_product_to_order('Coca-Cola'));
+    steps = steps.concat(add_product_to_order('Minute Maid'));
+    steps = steps.concat(verify_order_total('4.40'));
+    steps = steps.concat(goto_payment_screen_and_select_payment_method());
+    steps = steps.concat(generate_payment_screen_keypad_steps('6.05'));
+    steps = steps.concat(finish_order());
+    steps = steps.concat(verify_sync());
+    steps = steps.concat(open_table('T5', 1));
+    steps = steps.concat(verify_order_total('4.40'));
+    steps = steps.concat([{
+        content: 'start new order',
+        trigger: '.neworder-button',
+        run: 'click',
+    }]);
+    steps = steps.concat(add_product_to_order('Coca-Cola'));
+    steps = steps.concat(add_product_to_order('Minute Maid'));
+    steps = steps.concat([{
+        content: 'back to floor',
+        trigger: '.floor-button',
+        run: 'click',
+    }]);
+    steps = steps.concat(verify_sync());
+    steps = steps.concat(open_table('T5', 2));
+    steps = steps.concat([{
+        content: 'delete order',
+        trigger: '.deleteorder-button',
+        run: 'click',
+    }, {
+        content: 'confirm delete',
+        trigger: '.button.confirm',
+        run: 'click',
+    }, {
+        content: 'back to floor',
+        trigger: '.floor-button',
+        run: 'click',
+    }]);
+    steps = steps.concat(verify_sync());
+    steps = steps.concat(open_table('T5', 1));
+
+    steps = steps.concat([{
+        content: "close the Point of Sale frontend",
+        trigger: ".header-button",
+    }, {
+        content: "confirm closing the frontend",
+        trigger: ".header-button",
+        run: function() {}, //it's a check,
+    }, {
+        content: "close the Point of Sale frontend",
+        trigger: ".header-button",
+    }]);
+
+    Tour.register('pos_restaurant_sync', { test: true, url: '/pos/web' }, steps);
+
+
+    /* pos_restaurant_sync_second_login
+     *
+     * This tour should be run after the first tour is done.
+     */
+    var steps = [{
+        content: 'waiting for loading to finish',
+        trigger: 'body:has(.loader:hidden)',
+        run: function () {},
+    }];
+    steps = steps.concat(open_table('T5', 1));
+    steps = steps.concat(verify_order_total('4.40'));
+
+    steps = steps.concat(goto_payment_screen_and_select_payment_method());
+    steps = steps.concat(generate_payment_screen_keypad_steps('4.40'));
+    steps = steps.concat(finish_order());
+    steps = steps.concat(open_table('T2'));
+    steps = steps.concat(add_product_to_order('Coca-Cola'));
+    steps = steps.concat(verify_order_total('2.20'));
+    steps = steps.concat([{
+        content: 'back to floor',
+        trigger: '.floor-button',
+        run: 'click',
+    }]);
+    steps = steps.concat(verify_sync());
+    steps = steps.concat([{
+        content: "close the Point of Sale frontend",
+        trigger: ".header-button",
+    }, {
+        content: "confirm closing the frontend",
+        trigger: ".header-button",
+        run: function() {}, //it's a check,
+    }, {
+        content: "close the Point of Sale frontend",
+        trigger: ".header-button",
+    }]);
+
+    Tour.register('pos_restaurant_sync_second_login', { test: true, url: '/pos/web' }, steps);
+
+});
diff --git a/addons/pos_restaurant/tests/__init__.py b/addons/pos_restaurant/tests/__init__.py
new file mode 100644
index 00000000000..6f4bae0c7a2
--- /dev/null
+++ b/addons/pos_restaurant/tests/__init__.py
@@ -0,0 +1,4 @@
+# -*- coding: utf-8 -*-
+# Part of Odoo. See LICENSE file for full copyright and licensing details.
+
+from . import test_frontend
diff --git a/addons/pos_restaurant/tests/test_frontend.py b/addons/pos_restaurant/tests/test_frontend.py
new file mode 100644
index 00000000000..9ad26b2b440
--- /dev/null
+++ b/addons/pos_restaurant/tests/test_frontend.py
@@ -0,0 +1,76 @@
+# -*- coding: utf-8 -*-
+# Part of Odoo. See LICENSE file for full copyright and licensing details.
+
+import odoo.tests
+
+
+class TestFrontend(odoo.tests.HttpCase):
+
+    def test_01_pos_restaurant(self):
+        env = self.env(user=self.env.ref('base.user_admin'))
+        account_obj = env['account.account']
+
+        pos_config = env.ref('pos_restaurant.pos_config_restaurant')
+        main_company = env.ref('base.main_company')
+
+        account_receivable = account_obj.create({'code': 'X1012',
+                                                 'name': 'Account Receivable - Test',
+                                                 'user_type_id': env.ref('account.data_account_type_receivable').id,
+                                                 'reconcile': True})
+        field = env['ir.model.fields']._get('res.partner', 'property_account_receivable_id')
+        env['ir.property'].create({'name': 'property_account_receivable_id',
+                                   'company_id': main_company.id,
+                                   'fields_id': field.id,
+                                   'value': 'account.account,' + str(account_receivable.id)})
+        test_sale_journal = env['account.journal'].create({
+            'name': 'Sales Journal - Test',
+            'code': 'TSJ',
+            'type': 'sale',
+            'company_id': main_company.id
+            })
+
+        cash_journal = env['account.journal'].create({
+            'name': 'Cash Test',
+            'code': 'TCJ',
+            'type': 'sale',
+            'company_id': main_company.id
+            })
+
+        pos_config.write({
+            'journal_id': test_sale_journal.id,
+            'invoice_journal_id': test_sale_journal.id,
+            'payment_method_ids': [(0, 0, {
+                'name': 'Cash restaurant',
+                'split_transactions': True,
+                'receivable_account_id': account_receivable.id,
+                'is_cash_count': True,
+                'cash_journal_id': cash_journal.id,
+            })],
+        })
+
+        coke = self.env.ref('pos_restaurant.coke')
+        coke.write({'taxes_id': [(6, 0, [])]})
+        water = self.env.ref('pos_restaurant.water')
+        water.write({'taxes_id': [(6, 0, [])]})
+        minute_maid = self.env.ref('pos_restaurant.minute_maid')
+        minute_maid.write({'taxes_id': [(6, 0, [])]})
+
+        pos_config.open_session_cb()
+
+        # needed because tests are run before the module is marked as
+        # installed. In js web will only load qweb coming from modules
+        # that are returned by the backend in module_boot. Without
+        # this you end up with js, css but no qweb.
+        env['ir.module.module'].search([('name', '=', 'pos_restaurant')], limit=1).state = 'installed'
+
+
+        self.start_tour("/pos/web?config_id=%d" % pos_config.id, 'pos_restaurant_sync', login="admin")
+
+        self.assertEqual(1, env['pos.order'].search_count([('amount_total', '=', 4.4), ('state', '=', 'draft')]))
+        self.assertEqual(1, env['pos.order'].search_count([('amount_total', '=', 4.4), ('state', '=', 'paid')]))
+
+        self.start_tour("/pos/web?config_id=%d" % pos_config.id, 'pos_restaurant_sync_second_login', login="admin")
+
+        self.assertEqual(0, env['pos.order'].search_count([('amount_total', '=', 4.4), ('state', '=', 'draft')]))
+        self.assertEqual(1, env['pos.order'].search_count([('amount_total', '=', 2.2), ('state', '=', 'draft')]))
+        self.assertEqual(2, env['pos.order'].search_count([('amount_total', '=', 4.4), ('state', '=', 'paid')]))
diff --git a/addons/pos_restaurant/views/pos_restaurant_templates.xml b/addons/pos_restaurant/views/pos_restaurant_templates.xml
index 61db4c44e24..3143cff8d02 100644
--- a/addons/pos_restaurant/views/pos_restaurant_templates.xml
+++ b/addons/pos_restaurant/views/pos_restaurant_templates.xml
@@ -15,4 +15,11 @@
           </xpath>
         </template>
 
+    <template id="assets_backend" name="hr assets" inherit_id="web.assets_backend">
+        <xpath expr="." position="inside">
+            <link rel="stylesheet" type="text/scss" href="/point_of_sale/static/src/scss/pos_dashboard.scss"/>
+            <script type="text/javascript" src="/pos_restaurant/static/src/js/tours/pos_restaurant.js"></script>
+        </xpath>
+    </template>
+
 </odoo>