diff --git a/addons/sale/models/sale.py b/addons/sale/models/sale.py
index 90c57b40060..81ec265ef4e 100644
--- a/addons/sale/models/sale.py
+++ b/addons/sale/models/sale.py
@@ -505,18 +505,11 @@ class SaleOrder(models.Model):
         if field.name != 'invoice_status' or self.env.context.get('mail_activity_automation_skip'):
             return
 
-        filtered_self = self.filtered(lambda so: so.user_id and so.invoice_status == 'upselling')
-        if not filtered_self:
+        upselling_orders = self.filtered(lambda so: (so.user_id or so.partner_id.user_id) and so.invoice_status == 'upselling')
+        if not upselling_orders:
             return
 
-        filtered_self.activity_unlink(['sale.mail_act_sale_upsell'])
-        for order in filtered_self:
-            order.activity_schedule(
-                'sale.mail_act_sale_upsell',
-                user_id=order.user_id.id,
-                note=_("Upsell <a href='#' data-oe-model='%s' data-oe-id='%d'>%s</a> for customer <a href='#' data-oe-model='%s' data-oe-id='%s'>%s</a>") % (
-                         order._name, order.id, order.name,
-                         order.partner_id._name, order.partner_id.id, order.partner_id.display_name))
+        upselling_orders._create_upsell_activity()
 
     def copy_data(self, default=None):
         if default is None:
@@ -549,6 +542,17 @@ class SaleOrder(models.Model):
                 return self._search(domain, limit=limit, access_rights_uid=name_get_uid)
         return super(SaleOrder, self)._name_search(name, args=args, operator=operator, limit=limit, name_get_uid=name_get_uid)
 
+    def _create_upsell_activity(self):
+        self and self.activity_unlink(['sale.mail_act_sale_upsell'])
+        for order in self:
+            ref = "<a href='#' data-oe-model='%s' data-oe-id='%d'>%s</a>"
+            order_ref = ref % (order._name, order.id, order.name)
+            customer_ref = ref % (order.partner_id._name, order.partner_id.id, order.partner_id.display_name)
+            order.activity_schedule(
+                'sale.mail_act_sale_upsell',
+                user_id=order.user_id.id or order.partner_id.user_id.id,
+                note=_("Upsell %(order)s for customer %(customer)s", order=order_ref, customer=customer_ref))
+
     def _prepare_invoice(self):
         """
         Prepare the dict of values to create the new invoice for a sales order. This method may be
diff --git a/addons/sale_timesheet/models/product.py b/addons/sale_timesheet/models/product.py
index ce16030a947..8067d837487 100644
--- a/addons/sale_timesheet/models/product.py
+++ b/addons/sale_timesheet/models/product.py
@@ -21,6 +21,8 @@ class ProductTemplate(models.Model):
     # override domain
     project_id = fields.Many2one(domain="[('allow_billable', '=', True), ('pricing_type', '=', 'task_rate'), ('allow_timesheets', 'in', [service_policy == 'delivered_timesheet' or '', True])]")
     project_template_id = fields.Many2one(domain="[('allow_billable', '=', True), ('pricing_type', 'in', ('fixed_rate', 'employee_rate')), ('allow_timesheets', 'in', [service_policy == 'delivered_timesheet' or '', True])]")
+    service_upsell_warning = fields.Boolean('Upsell Warning', help="The salesperson in charge will be assigned an activity informing him of an upselling opportunity once the selected threshold is reached.")
+    service_upsell_threshold = fields.Float('Threshold', help="Percentage of time delivered compared to the prepaid amount that must be reached for the upselling opportunity activity to be triggered.")
 
     def _default_visible_expense_policy(self):
         visibility = self.user_has_groups('project.group_project_user')
diff --git a/addons/sale_timesheet/models/sale_order.py b/addons/sale_timesheet/models/sale_order.py
index 2f26feba436..8bb46eaa28e 100644
--- a/addons/sale_timesheet/models/sale_order.py
+++ b/addons/sale_timesheet/models/sale_order.py
@@ -5,6 +5,7 @@ import math
 
 from odoo import api, fields, models, _
 from odoo.osv import expression
+from odoo.tools import float_compare
 
 
 class SaleOrder(models.Model):
@@ -42,6 +43,46 @@ class SaleOrder(models.Model):
             total_time *= sale_order.timesheet_encode_uom_id.factor
             sale_order.timesheet_total_duration = round(total_time)
 
+    def _compute_field_value(self, field):
+        super()._compute_field_value(field)
+        if field.name != 'invoice_status' or self.env.context.get('mail_activity_automation_skip'):
+            return
+
+        # Get SOs which their state is not equal to upselling or invoied and if at least a SOL has warning prepaid service upsell set to True and the warning has not already been displayed
+        upsellable_orders = self.filtered(lambda so:
+            so.state == 'sale'
+            and so.invoice_status not in ('upselling', 'invoiced')
+            and (so.user_id or so.partner_id.user_id)  # salesperson needed to assign upsell activity
+        )
+        for order in upsellable_orders:
+            upsellable_lines = order._get_prepaid_service_lines_to_upsell()
+            if upsellable_lines:
+                order._create_upsell_activity()
+                # We want to display only one time the warning for each SOL
+                upsellable_lines.write({'has_displayed_warning_upsell': True})
+
+    def _get_prepaid_service_lines_to_upsell(self):
+        """ Retrieve all sols which need to display an upsell activity warning in the SO
+
+            These SOLs should contain a product which has:
+                - type="service",
+                - service_policy="ordered_timesheet",
+                - service_upsell_warning=True.
+        """
+        self.ensure_one()
+        precision = self.env['decimal.precision'].precision_get('Product Unit of Measure')
+        return self.order_line.filtered(lambda sol:
+            sol.is_service
+            and not sol.has_displayed_warning_upsell  # we don't want to display many times the warning each time we timesheet on the SOL
+            and sol.product_id.service_policy == 'ordered_timesheet'
+            and sol.product_id.service_upsell_warning
+            and float_compare(
+                sol.qty_delivered,
+                sol.product_uom_qty * (sol.product_id.service_upsell_threshold or 1.0),
+                precision_digits=precision
+            ) >= 0
+        )
+
     def action_view_project_ids(self):
         self.ensure_one()
         # redirect to form or kanban view
@@ -81,6 +122,7 @@ class SaleOrderLine(models.Model):
     analytic_line_ids = fields.One2many(domain=[('project_id', '=', False)])  # only analytic lines, not timesheets (since this field determine if SO line came from expense)
     remaining_hours_available = fields.Boolean(compute='_compute_remaining_hours_available', compute_sudo=True)
     remaining_hours = fields.Float('Remaining Hours on SO', compute='_compute_remaining_hours', compute_sudo=True, store=True)
+    has_displayed_warning_upsell = fields.Boolean('Has Displayed Warning Upsell')
 
     def name_get(self):
         res = super(SaleOrderLine, self).name_get()
diff --git a/addons/sale_timesheet/tests/__init__.py b/addons/sale_timesheet/tests/__init__.py
index 4f78edeef69..dd7859481f1 100644
--- a/addons/sale_timesheet/tests/__init__.py
+++ b/addons/sale_timesheet/tests/__init__.py
@@ -9,3 +9,4 @@ from . import test_reinvoice
 from . import test_reporting
 from . import test_project_overview
 from . import test_project_billing_multicompany
+from . import test_upsell_warning
diff --git a/addons/sale_timesheet/tests/test_upsell_warning.py b/addons/sale_timesheet/tests/test_upsell_warning.py
new file mode 100644
index 00000000000..e7e7fda1762
--- /dev/null
+++ b/addons/sale_timesheet/tests/test_upsell_warning.py
@@ -0,0 +1,89 @@
+# -*- coding: utf-8 -*-
+# Part of Odoo. See LICENSE file for full copyright and licensing details.
+
+from odoo.tests import tagged
+
+from .common import TestCommonSaleTimesheet
+
+
+@tagged('-at_install', 'post_install')
+class TestUpsellWarning(TestCommonSaleTimesheet):
+    def test_display_upsell_warning(self):
+        """ Test to display an upsell warning
+
+
+            We display an upsell warning in SO when this following condition is satisfy in its SOL:
+            (qty_delivered / product_uom_qty) >= product_id.service_upsell_threshold
+
+            Test Case:
+            =========
+            1) Configure the upsell warning in prepaid service product
+            2) Create SO with a SOL containing this updated product,
+            3) Create Project and Task,
+            4) Timesheet in the task to satisfy the condition for the SOL to display an upsell warning,
+            5) Check if the SO has an 'sale.mail_act_sale_upsell' activity.
+        """
+        # 1) Configure the upsell warning in prepaid service product
+        self.product_order_timesheet1.write({
+            'service_upsell_warning': True,
+            'service_upsell_threshold': 0.6,
+        })
+
+        # 2) Create SO with a SOL containing this updated product
+        so = self.env['sale.order'].create({
+            'partner_id': self.partner_a.id,
+            'partner_invoice_id': self.partner_a.id,
+            'partner_shipping_id': self.partner_a.id,
+        })
+
+        self.env['sale.order.line'].create({
+            'order_id': so.id,
+            'name': self.product_order_timesheet1.name,
+            'product_id': self.product_order_timesheet1.id,
+            'product_uom_qty': 10,
+            'price_unit': self.product_order_timesheet1.list_price,
+        })
+        so.action_confirm()
+
+        # 3) Create Project and Task
+        project = self.env['project.project'].create({
+            'name': 'Project',
+            'allow_timesheets': True,
+            'allow_billable': True,
+            'partner_id': self.partner_a.id,
+            'analytic_account_id': self.analytic_account_sale.id,
+        })
+        task = self.env['project.task'].create({
+            'name': 'Task Test',
+            'project_id': project.id,
+        })
+        task._compute_sale_line()
+
+        # 4) Timesheet in the task to satisfy the condition for the SOL to display an upsell warning
+        timesheet = self.env['account.analytic.line'].create({
+            'name': 'Test Line',
+            'unit_amount': 5,
+            'employee_id': self.employee_manager.id,
+            'project_id': project.id,
+            'task_id': task.id,
+        })
+        timesheet._compute_so_line()
+        so.order_line._compute_qty_delivered()
+        so.order_line._compute_invoice_status()
+        so._get_invoice_status()
+        # Normally this method is called at the end of _get_invoice_status and other compute method. Here, we simulate for invoice_status field
+        so._compute_field_value(so._fields['invoice_status'])
+
+        self.assertEqual(len(so.activity_search(['sale.mail_act_sale_upsell'])), 0, 'No upsell warning should appear in the SO.')
+        timesheet.write({
+            'unit_amount': 6,
+        })
+        timesheet._compute_so_line()
+        so.order_line._compute_qty_delivered()
+        so.order_line._compute_invoice_status()
+        so._get_invoice_status()
+        # Normally this method is called at the end of _get_invoice_status and other compute method. Here, we simulate for invoice_status field
+        so._compute_field_value(so._fields['invoice_status'])
+
+        # 5) Check if the SO has an 'sale.mail_act_sale_upsell' activity.
+        self.assertEqual(len(so.activity_search(['sale.mail_act_sale_upsell'])), 1, 'A upsell warning should appear in the SO.')
diff --git a/addons/sale_timesheet/views/product_views.xml b/addons/sale_timesheet/views/product_views.xml
index d238c6ea8ca..b14eb21afa4 100644
--- a/addons/sale_timesheet/views/product_views.xml
+++ b/addons/sale_timesheet/views/product_views.xml
@@ -11,6 +11,8 @@
             </xpath>
             <xpath expr="//field[@name='service_type']" position="after">
                 <field name="service_policy" widget="radio" attrs="{'invisible': [('type','!=','service')]}"/>
+                <field name="service_upsell_warning" attrs="{'invisible': ['|', ('type', '!=', 'service'), ('service_policy', '!=', 'ordered_timesheet')]}" />
+                <field name="service_upsell_threshold" attrs="{'invisible': ['|', '|', ('type', '!=', 'service'), ('service_policy', '!=', 'ordered_timesheet'), ('service_upsell_warning', '=', False)]}" widget="percentage"/>
             </xpath>
         </field>
     </record>