diff --git a/addons/account/account_invoice_view.xml b/addons/account/account_invoice_view.xml
index eb196fa6a8e..e04b7c74a99 100644
--- a/addons/account/account_invoice_view.xml
+++ b/addons/account/account_invoice_view.xml
@@ -52,7 +52,7 @@
                 <form string="Invoice Line">
                     <notebook>
                         <page string="Line">
-                            <field name="product_id" on_change="product_id_change(product_id, uos_id, quantity, name, parent.type, parent.partner_id)" select="1"/>
+                            <field name="product_id" on_change="product_id_change(product_id, uos_id, quantity, name, parent.type, parent.partner_id, parent.fiscal_position)" select="1"/>
                             <field name="uos_id"/>
                             <field name="quantity" select="1"/>
                             <field name="price_unit" select="1"/>
@@ -154,8 +154,8 @@
                             <field name="check_total" required="2"/>
                             <field colspan="4" default_get="{'check_total': check_total, 'invoice_line': invoice_line, 'address_invoice_id': address_invoice_id, 'partner_id': partner_id, 'price_type': 'price_type' in dir() and price_type or False}" name="invoice_line" nolabel="1">
                                 <tree string="Invoice lines" editable="top">
-                                    <field name="product_id" on_change="product_id_change(product_id, uos_id, quantity, name, parent.type, parent.partner_id, price_unit, parent.address_invoice_id)"/>
-                                    <field domain="[('company_id', '=', parent.company_id), ('journal_id', '=', parent.journal_id), ('type', '&lt;&gt;', 'view')]" name="account_id" on_change="onchange_account_id(parent.partner_id,account_id)"/>
+                                    <field name="product_id" on_change="product_id_change(product_id, uos_id, quantity, name, parent.type, parent.partner_id, parent.fiscal_position, price_unit, parent.address_invoice_id)"/>
+                                    <field domain="[('company_id', '=', parent.company_id), ('journal_id', '=', parent.journal_id), ('type', '&lt;&gt;', 'view')]" name="account_id" on_change="onchange_account_id(parent.fiscal_position,account_id)"/>
                                     <field name="invoice_line_tax_id" view_mode="2" domain="[('parent_id','=',False)]"/>
                                     <field domain="[('type','&lt;&gt;','view'), ('company_id', '=', parent.company_id)]" name="account_analytic_id"/>
                                     <field name="quantity"/>
diff --git a/addons/account/invoice.py b/addons/account/invoice.py
index a560b094b40..06f604c6a1f 100644
--- a/addons/account/invoice.py
+++ b/addons/account/invoice.py
@@ -320,8 +320,7 @@ class account_invoice(osv.osv):
                 acc_id = p.property_account_receivable.id
             else:
                 acc_id = p.property_account_payable.id
-            if p.property_account_position:
-                fiscal_position = p.property_account_position.id
+            fiscal_position = p.property_account_position and p.property_account_position.id or False
             partner_payment_term = p.property_payment_term and p.property_payment_term.id or False
             if p.bank_ids:
                 bank_id = p.bank_ids[0].id
@@ -950,7 +949,7 @@ class account_invoice_line(osv.osv):
                 price_unit = price_unit - tax['amount']
         return {'price_unit': price_unit,'invoice_line_tax_id': tax_id}
 
-    def product_id_change(self, cr, uid, ids, product, uom, qty=0, name='', type='out_invoice', partner_id=False, price_unit=False, address_invoice_id=False, context=None):
+    def product_id_change(self, cr, uid, ids, product, uom, qty=0, name='', type='out_invoice', partner_id=False, fposition_id=False, price_unit=False, address_invoice_id=False, context=None):
         if context is None:
             context = {}
         if not partner_id:
@@ -961,15 +960,17 @@ class account_invoice_line(osv.osv):
             else:
                 return {'value': {'price_unit': 0.0}, 'domain':{'product_uom':[]}}
         part = self.pool.get('res.partner').browse(cr, uid, partner_id)
+        fpos = fposition_id and self.pool.get('account.fiscal.position').browse(cr, uid, fposition_id) or False
+
         lang=part.lang
         context.update({'lang': lang})
         res = self.pool.get('product.product').browse(cr, uid, product, context=context)
         taxep=None
         tax_obj = self.pool.get('account.tax')
         if type in ('out_invoice', 'out_refund'):
-            tax_id = self.pool.get('account.fiscal.position').map_tax(cr, uid, part, res.taxes_id)
+            tax_id = self.pool.get('account.fiscal.position').map_tax(cr, uid, fpos, res.taxes_id)
         else:
-            tax_id = self.pool.get('account.fiscal.position').map_tax(cr, uid, part, res.supplier_taxes_id)
+            tax_id = self.pool.get('account.fiscal.position').map_tax(cr, uid, fpos, res.supplier_taxes_id)
         if type in ('in_invoice', 'in_refund'):
             result = self.product_id_change_unit_price_inv(cr, uid, tax_id, price_unit, qty, address_invoice_id, product, partner_id, context=context)
         else:
@@ -987,7 +988,7 @@ class account_invoice_line(osv.osv):
             if not a:
                 a = res.categ_id.property_account_expense_categ.id
 
-        a = self.pool.get('account.fiscal.position').map_account(cr, uid, part, a)
+        a = self.pool.get('account.fiscal.position').map_account(cr, uid, fpos, a)
         if a:
             result['account_id'] = a
 
@@ -1057,13 +1058,12 @@ class account_invoice_line(osv.osv):
     #
     # Set the tax field according to the account and the partner
     #
-    def onchange_account_id(self, cr, uid, ids, partner_id,account_id):
-        if not (partner_id and account_id):
+    def onchange_account_id(self, cr, uid, ids, fposition_id, account_id):
+        if not (fposition_id and account_id):
             return {}
         taxes = self.pool.get('account.account').browse(cr, uid, account_id).tax_ids
-        part = self.pool.get('res.partner').browse(cr, uid, partner_id)
-
-        res = self.pool.get('account.fiscal.position').map_tax(cr, uid, part, taxes)
+        fpos = fposition_id and self.pool.get('account.fiscal.position').browse(cr, uid, fposition_id) or False
+        res = self.pool.get('account.fiscal.position').map_tax(cr, uid, fpos, taxes)
         r = {'value':{'invoice_line_tax_id': res}}
         return r
 account_invoice_line()
diff --git a/addons/account/partner.py b/addons/account/partner.py
index a2e981fb4ab..9cfe5e3bf1b 100644
--- a/addons/account/partner.py
+++ b/addons/account/partner.py
@@ -32,14 +32,15 @@ class account_fiscal_position(osv.osv):
         'account_ids': fields.one2many('account.fiscal.position.account', 'position_id', 'Accounts Mapping'),
         'tax_ids': fields.one2many('account.fiscal.position.tax', 'position_id', 'Taxes Mapping')
     }
-    def map_tax(self, cr, uid, partner, taxes, context={}):
-        if (not partner) or (not partner.property_account_position) :
+
+    def map_tax(self, cr, uid, fposition_id, taxes, context={}):
+        if not fposition_id:
             return map(lambda x: x.id, taxes)
         result = []
         for t in taxes:
             ok = False
-            for tax in partner.property_account_position.tax_ids:
-                if tax.tax_src_id.id==t.id:
+            for tax in fposition_id.tax_ids:
+                if tax.tax_src_id.id == t.id:
                     if tax.tax_dest_id:
                         result.append(tax.tax_dest_id.id)
                     ok=True
@@ -47,10 +48,10 @@ class account_fiscal_position(osv.osv):
                 result.append(t.id)
         return result
 
-    def map_account(self, cr, uid, partner, account_id, context={}):
-        if (not partner) or (not partner.property_account_position) :
+    def map_account(self, cr, uid, fposition_id, account_id, context={}):
+        if not fposition_id :
             return account_id
-        for pos in partner.property_account_position.account_ids:
+        for pos in fposition_id.account_ids:
             if pos.account_src_id.id==account_id:
                 account_id = pos.account_dest_id.id
                 break