diff --git a/modules/account/tax.py b/modules/account/tax.py
index a7f8ab6b40..f016eed00c 100644
--- a/modules/account/tax.py
+++ b/modules/account/tax.py
@@ -1,5 +1,6 @@
 # This file is part of Tryton.  The COPYRIGHT file at the top level of
 # this repository contains the full copyright notices and license terms.
+import copy
 import datetime
 from collections import defaultdict, namedtuple
 from decimal import Decimal
@@ -1173,21 +1174,37 @@ class Tax(sequence_ordered(), ModelSQL, ModelView, DeactivableMixin):
         cls.save(to_save)
 
 
-class _TaxKey(dict):
+class _TaxLine:
+    __slots__ = ('base', 'amount', 'tax', 'account')
 
     def __init__(self, **kwargs):
-        self.update(kwargs)
+        for k, v in kwargs.items():
+            setattr(self, k, v)
 
+    def values(self):
+        for k in self.__slots__:
+            yield k, getattr(self, k)
+
+    @property
     def _key(self):
-        return (self['account'], self['tax'], self['base'] >= 0)
+        return (self.account, self.tax, self.base >= 0)
 
-    def __eq__(self, other):
-        if isinstance(other, _TaxKey):
-            return self._key() == other._key()
-        return self._key() == other
+    def __add__(self, other):
+        if (not isinstance(other, _TaxLine)
+                or self._key != other._key):
+            return NotImplemented
+        new = copy.copy(self)
+        for key in ['base', 'amount']:
+            setattr(new, key, getattr(self, key) + getattr(other, key))
+        return new
 
-    def __hash__(self):
-        return hash(self._key())
+    def __iadd__(self, other):
+        if (not isinstance(other, _TaxLine)
+                or self._key != other._key):
+            return NotImplemented
+        for key in ['base', 'amount']:
+            setattr(self, key, getattr(self, key) + getattr(other, key))
+        return self
 
 
 class _TaxableLine(namedtuple(
@@ -1223,23 +1240,21 @@ class TaxableMixin(object):
     def _get_tax_context(self):
         return {}
 
-    @staticmethod
-    def _compute_tax_line(amount, base, tax):
+    def _compute_tax_line(self, amount, base, tax):
         if base >= 0:
             type_ = 'invoice'
         else:
             type_ = 'credit_note'
-
-        line = {}
-        line['manual'] = False
-        line['description'] = tax.description
-        line['legal_notice'] = tax.legal_notice
-        line['base'] = base
-        line['amount'] = amount
-        line['tax'] = tax.id
-        line['account'] = getattr(tax, '%s_account' % type_).id
-
-        return _TaxKey(**line)
+        # Base must always be rounded per line as there will be
+        # one tax line per taxable_lines
+        if self.currency:
+            base = self.currency.round(base)
+        return _TaxLine(
+            base=base,
+            amount=amount,
+            tax=tax,
+            account=getattr(tax, '%s_account' % type_),
+            )
 
     def _round_taxes(self, taxes):
         if not self.currency:
@@ -1247,9 +1262,9 @@ class TaxableMixin(object):
 
         remainder = 0
         for taxline in taxes.values():
-            rounded_amount = self.currency.round(taxline['amount'])
-            remainder += rounded_amount - taxline['amount']
-            taxline['amount'] = rounded_amount
+            rounded_amount = self.currency.round(taxline.amount)
+            remainder += rounded_amount - taxline.amount
+            taxline.amount = rounded_amount
 
         # We need to compensate the rounding we did
         remainder = self.currency.round(remainder, opposite=True)
@@ -1257,8 +1272,8 @@ class TaxableMixin(object):
             offset_amount = self.currency.rounding.copy_sign(remainder)
 
             for tax in cycle(taxes.values()):
-                if tax['amount']:
-                    tax['amount'] -= offset_amount
+                if tax.amount:
+                    tax.amount -= offset_amount
                     remainder -= offset_amount
                     if abs(remainder) < self.currency.rounding:
                         break
@@ -1291,33 +1306,25 @@ class TaxableMixin(object):
                     current_taxes = {}
                     for tax in l_taxes:
                         taxline = self._compute_tax_line(**tax)
-                        # Base must always be rounded per line as there will be
-                        # one tax line per taxable_lines
-                        if self.currency:
-                            taxline['base'] = self.currency.round(
-                                taxline['base'])
+                        key = taxline._key
                         if taxline not in current_taxes:
-                            current_taxes[taxline] = taxline
+                            current_taxes[key] = taxline
                         else:
-                            current_taxes[taxline]['base'] += taxline['base']
-                            current_taxes[taxline]['amount'] += (
-                                taxline['amount'])
+                            current_taxes[key] += taxline
                     if tax_rounding == 'line':
                         self._round_taxes(current_taxes)
                     for key, taxline in current_taxes.items():
                         if key not in taxes:
                             taxes[key] = taxline
                         else:
-                            taxes[key]['base'] += taxline['base']
-                            taxes[key]['amount'] += taxline['amount']
+                            taxes[key] += taxline
                 if tax_rounding == 'document':
                     self._round_taxes(taxes)
                 for key, taxline in taxes.items():
                     if key not in all_taxes:
                         all_taxes[key] = taxline
                     else:
-                        all_taxes[key]['base'] += taxline['base']
-                        all_taxes[key]['amount'] += taxline['amount']
+                        all_taxes[key] += taxline
         return all_taxes
 
 
@@ -1919,17 +1926,14 @@ class TestTaxView(ModelView, TaxableMixin):
         Result = pool.get('account.tax.test.result')
         result = []
         if all([self.tax_date, self.unit_price, self.quantity, self.currency]):
-            for taxline in self._get_taxes():
-                del taxline['manual']
-                result.append(Result(**taxline))
+            for taxline in self._get_taxes().values():
+                result.append(Result(**dict(taxline.values())))
         return result
 
 
 class TestTaxViewResult(ModelView):
     __name__ = 'account.tax.test.result'
     tax = fields.Many2One('account.tax', "Tax")
-    description = fields.Char("Description")
-    legal_notice = fields.Char("Legal Notice")
     account = fields.Many2One('account.account', "Account")
     base = fields.Numeric("Base")
     amount = fields.Numeric("Amount")
diff --git a/modules/account/tests/test_module.py b/modules/account/tests/test_module.py
index d76b394866..a6c194e251 100644
--- a/modules/account/tests/test_module.py
+++ b/modules/account/tests/test_module.py
@@ -1257,11 +1257,11 @@ class AccountTestCase(
                     ] * 100,
                 company=company)
 
-            taxes = taxable._get_taxes()
+            taxes = taxable._get_taxes().values()
 
         tax, = taxes
-        self.assertEqual(tax['base'], Decimal('100.00'))
-        self.assertEqual(tax['amount'], Decimal('20.00'))
+        self.assertEqual(tax.base, Decimal('100.00'))
+        self.assertEqual(tax.amount, Decimal('20.00'))
 
     @with_transaction()
     def test_taxable_mixin_line2(self):
@@ -1289,11 +1289,11 @@ class AccountTestCase(
                     ],
                 company=company)
 
-            taxes = taxable._get_taxes()
+            taxes = taxable._get_taxes().values()
 
         tax, = taxes
-        self.assertEqual(tax['base'], Decimal('2.07'))
-        self.assertEqual(tax['amount'], Decimal('2.07'))
+        self.assertEqual(tax.base, Decimal('2.07'))
+        self.assertEqual(tax.amount, Decimal('2.07'))
 
     @with_transaction()
     def test_taxable_mixin_document(self):
@@ -1318,11 +1318,11 @@ class AccountTestCase(
                     ] * 100,
                 company=company)
 
-            taxes = taxable._get_taxes()
+            taxes = taxable._get_taxes().values()
 
         tax, = taxes
-        self.assertEqual(tax['base'], Decimal('100.00'))
-        self.assertEqual(tax['amount'], Decimal('20.02'))
+        self.assertEqual(tax.base, Decimal('100.00'))
+        self.assertEqual(tax.amount, Decimal('20.02'))
 
     @with_transaction()
     def test_taxable_mixin_many_taxable_lines(self):
@@ -1345,15 +1345,15 @@ class AccountTestCase(
                     ],
                 company=company)
 
-            taxes = taxable._get_taxes()
+            taxes = taxable._get_taxes().values()
 
         self.assertEqual(len(taxes), 2)
-        tax_line1, = [t for t in taxes if t['tax'] == tax1.id]
-        tax_line2, = [t for t in taxes if t['tax'] == tax2.id]
-        self.assertEqual(tax_line1['base'], Decimal('30.00'))
-        self.assertEqual(tax_line1['amount'], Decimal('3.00'))
-        self.assertEqual(tax_line2['base'], Decimal('20.00'))
-        self.assertEqual(tax_line2['amount'], Decimal('4.00'))
+        tax_line1, = [t for t in taxes if t.tax == tax1]
+        tax_line2, = [t for t in taxes if t.tax == tax2]
+        self.assertEqual(tax_line1.base, Decimal('30.00'))
+        self.assertEqual(tax_line1.amount, Decimal('3.00'))
+        self.assertEqual(tax_line2.base, Decimal('20.00'))
+        self.assertEqual(tax_line2.amount, Decimal('4.00'))
 
     @with_transaction()
     def test_taxable_mixin_tax_residual_rounding(self):
@@ -1398,11 +1398,11 @@ class AccountTestCase(
                     ],
                 company=company)
 
-            taxline_1, taxline_2 = taxable._get_taxes()
-            self.assertEqual(taxline_1['base'], Decimal('1.04'))
-            self.assertEqual(taxline_1['amount'], Decimal('.11'))
-            self.assertEqual(taxline_2['base'], Decimal('1.04'))
-            self.assertEqual(taxline_2['amount'], Decimal('.10'))
+            taxline_1, taxline_2 = taxable._get_taxes().values()
+            self.assertEqual(taxline_1.base, Decimal('1.04'))
+            self.assertEqual(taxline_1.amount, Decimal('.11'))
+            self.assertEqual(taxline_2.base, Decimal('1.04'))
+            self.assertEqual(taxline_2.amount, Decimal('.10'))
 
     @with_transaction()
     def test_taxable_mixin_tax_residual_rounding_with_0(self):
@@ -1454,13 +1454,13 @@ class AccountTestCase(
                     ],
                 company=company)
 
-            taxline_0, taxline_1, taxline_2 = taxable._get_taxes()
-            self.assertEqual(taxline_0['base'], Decimal('1.04'))
-            self.assertEqual(taxline_0['amount'], Decimal('0'))
-            self.assertEqual(taxline_1['base'], Decimal('1.04'))
-            self.assertEqual(taxline_1['amount'], Decimal('.11'))
-            self.assertEqual(taxline_2['base'], Decimal('1.04'))
-            self.assertEqual(taxline_2['amount'], Decimal('.10'))
+            taxline_0, taxline_1, taxline_2 = taxable._get_taxes().values()
+            self.assertEqual(taxline_0.base, Decimal('1.04'))
+            self.assertEqual(taxline_0.amount, Decimal('0'))
+            self.assertEqual(taxline_1.base, Decimal('1.04'))
+            self.assertEqual(taxline_1.amount, Decimal('.11'))
+            self.assertEqual(taxline_2.base, Decimal('1.04'))
+            self.assertEqual(taxline_2.amount, Decimal('.10'))
 
     @with_transaction()
     def test_taxable_mixin_tax_residual_rounding_negative_residual(self):
@@ -1507,13 +1507,13 @@ class AccountTestCase(
                     ],
                 company=company)
 
-            taxline_1, taxline_2, taxline_3 = taxable._get_taxes()
-            self.assertEqual(taxline_1['base'], Decimal('30.00'))
-            self.assertEqual(taxline_1['amount'], Decimal('3.00'))
-            self.assertEqual(taxline_2['base'], Decimal('-2.95'))
-            self.assertEqual(taxline_2['amount'], Decimal('-0.29'))
-            self.assertEqual(taxline_3['base'], Decimal('-2.95'))
-            self.assertEqual(taxline_3['amount'], Decimal('-0.30'))
+            taxline_1, taxline_2, taxline_3 = taxable._get_taxes().values()
+            self.assertEqual(taxline_1.base, Decimal('30.00'))
+            self.assertEqual(taxline_1.amount, Decimal('3.00'))
+            self.assertEqual(taxline_2.base, Decimal('-2.95'))
+            self.assertEqual(taxline_2.amount, Decimal('-0.29'))
+            self.assertEqual(taxline_3.base, Decimal('-2.95'))
+            self.assertEqual(taxline_3.amount, Decimal('-0.30'))
 
     @with_transaction()
     def test_taxable_mixin_tax_residual_rounding_per_same_taxes(self):
@@ -1553,11 +1553,11 @@ class AccountTestCase(
                     ],
                 company=company)
 
-            taxline_1, taxline_2 = taxable._get_taxes()
-            self.assertEqual(taxline_1['base'], Decimal('11.72'))
-            self.assertEqual(taxline_1['amount'], Decimal('0.7'))
-            self.assertEqual(taxline_2['base'], Decimal('-0.45'))
-            self.assertEqual(taxline_2['amount'], Decimal('-0.03'))
+            taxline_1, taxline_2 = taxable._get_taxes().values()
+            self.assertEqual(taxline_1.base, Decimal('11.72'))
+            self.assertEqual(taxline_1.amount, Decimal('0.7'))
+            self.assertEqual(taxline_2.base, Decimal('-0.45'))
+            self.assertEqual(taxline_2.amount, Decimal('-0.03'))
 
     @with_transaction()
     def test_tax_compute_with_children_update_unit_price(self):
diff --git a/modules/account/view/tax_test_result_list.xml b/modules/account/view/tax_test_result_list.xml
index dd4c524480..d4108c2e46 100644
--- a/modules/account/view/tax_test_result_list.xml
+++ b/modules/account/view/tax_test_result_list.xml
@@ -6,6 +6,4 @@ this repository contains the full copyright notices and license terms. -->
     <field name="amount"/>
     <field name="account"/>
     <field name="tax"/>
-    <field name="description"/>
-    <field name="legal_notice"/>
 </tree>
diff --git a/modules/account_invoice/invoice.py b/modules/account_invoice/invoice.py
index 185d74acb3..f4f549e7d3 100644
--- a/modules/account_invoice/invoice.py
+++ b/modules/account_invoice/invoice.py
@@ -649,13 +649,14 @@ class Invoice(Workflow, ModelSQL, ModelView, TaxableMixin, InvoiceReportMixin):
         self.untaxed_amount = Decimal(0)
         self.tax_amount = Decimal(0)
         self.total_amount = Decimal(0)
-        computed_taxes = {}
 
         if self.lines:
             for line in self.lines:
                 if getattr(line, 'type', '') == 'line':
                     self.untaxed_amount += getattr(line, 'amount', 0) or 0
             computed_taxes = self._get_taxes()
+        else:
+            computed_taxes = {}
 
         def is_zero(amount):
             if self.currency:
@@ -663,7 +664,7 @@ class Invoice(Workflow, ModelSQL, ModelView, TaxableMixin, InvoiceReportMixin):
             else:
                 return amount == Decimal(0)
 
-        tax_keys = []
+        tax_keys = set()
         taxes = list(self.taxes or [])
         for tax in (self.taxes or []):
             if tax.manual:
@@ -673,20 +674,24 @@ class Invoice(Workflow, ModelSQL, ModelView, TaxableMixin, InvoiceReportMixin):
             if (key not in computed_taxes) or (key in tax_keys):
                 taxes.remove(tax)
                 continue
-            tax_keys.append(key)
-            if not is_zero(computed_taxes[key]['base']
-                    - (tax.base or Decimal(0))):
-                self.tax_amount += computed_taxes[key]['amount']
-                tax.amount = computed_taxes[key]['amount']
-                tax.base = computed_taxes[key]['base']
+            tax_keys.add(key)
+            if not is_zero(
+                    computed_taxes[key].base - (tax.base or Decimal(0))):
+                self.tax_amount += computed_taxes[key].amount
+                tax.amount = computed_taxes[key].amount
+                tax.base = computed_taxes[key].base
             else:
                 self.tax_amount += tax.amount or Decimal(0)
         for key in computed_taxes:
             if key not in tax_keys:
-                self.tax_amount += computed_taxes[key]['amount']
+                tax = computed_taxes[key].tax
+                self.tax_amount += computed_taxes[key].amount
                 value = InvoiceTax.default_get(
                     list(InvoiceTax._fields.keys()), with_rec_name=False)
-                value.update(computed_taxes[key])
+                value.update(computed_taxes[key].values())
+                value['manual'] = False
+                value['description'] = tax.description
+                value['legal_notice'] = tax.legal_notice
                 invoice_tax = InvoiceTax(**value)
                 if invoice_tax.tax:
                     invoice_tax.sequence = invoice_tax.tax.sequence
@@ -1080,10 +1085,13 @@ class Invoice(Workflow, ModelSQL, ModelView, TaxableMixin, InvoiceReportMixin):
         return context
 
     def _compute_taxes(self):
-        taxes = self._get_taxes()
-        for tax in taxes.values():
-            tax['invoice'] = self.id
-        return taxes
+        for key, tax_line in self._get_taxes().items():
+            value = dict(tax_line.values())
+            value['invoice'] = self.id
+            value['manual'] = False
+            value['description'] = tax_line.tax.description
+            value['legal_notice'] = tax_line.tax.legal_notice
+            yield key, value
 
     @dualmethod
     def update_taxes(cls, invoices, exception=False):
@@ -1094,11 +1102,11 @@ class Invoice(Workflow, ModelSQL, ModelView, TaxableMixin, InvoiceReportMixin):
         for invoice in invoices:
             if invoice.state in ('posted', 'paid', 'cancelled'):
                 continue
-            computed_taxes = invoice._compute_taxes()
+            computed_taxes = dict(invoice._compute_taxes())
             if not invoice.taxes:
                 to_create.extend(computed_taxes.values())
             else:
-                tax_keys = []
+                tax_keys = set()
                 for tax in invoice.taxes:
                     if tax.manual:
                         continue
@@ -1106,7 +1114,7 @@ class Invoice(Workflow, ModelSQL, ModelView, TaxableMixin, InvoiceReportMixin):
                     if (key not in computed_taxes) or (key in tax_keys):
                         to_delete.append(tax)
                         continue
-                    tax_keys.append(key)
+                    tax_keys.add(key)
                     if not invoice.currency.is_zero(
                             computed_taxes[key]['base'] - tax.base):
                         to_write.extend(([tax], computed_taxes[key]))
@@ -1114,6 +1122,7 @@ class Invoice(Workflow, ModelSQL, ModelView, TaxableMixin, InvoiceReportMixin):
                     if key not in tax_keys:
                         to_create.append(computed_taxes[key])
             if exception and (to_create or to_delete or to_write):
+                raise Exception(invoice.taxes, to_create, to_delete, to_write)
                 raise InvoiceTaxValidationError(
                     gettext('account_invoice.msg_invoice_tax_invalid',
                         invoice=invoice.rec_name))
@@ -2520,7 +2529,7 @@ class InvoiceLine(sequence_ordered(), ModelSQL, ModelView, TaxableMixin):
                     and self.taxes_deductible_rate != 1):
                 with Transaction().set_context(_deductible_rate=1):
                     tax_amount = sum(
-                        t['amount'] for t in self._get_taxes().values())
+                        t.amount for t in self._get_taxes().values())
                 non_deductible_amount = (
                     tax_amount * (1 - self.taxes_deductible_rate))
                 amount += non_deductible_amount
@@ -2603,7 +2612,7 @@ class InvoiceLine(sequence_ordered(), ModelSQL, ModelView, TaxableMixin):
     def get_invoice_taxes(self, name):
         if not self.invoice:
             return
-        taxes_keys = list(self._get_taxes().keys())
+        taxes_keys = self._get_taxes().keys()
         taxes = []
         for tax in self.invoice.taxes:
             if tax.manual:
@@ -2831,7 +2840,7 @@ class InvoiceLine(sequence_ordered(), ModelSQL, ModelView, TaxableMixin):
             return tax_lines
         taxes = self._get_taxes().values()
         for tax in taxes:
-            amount = tax['base']
+            amount = tax.base
             with Transaction().set_context(
                     date=self.invoice.currency_date):
                 amount = Currency.compute(
@@ -2840,7 +2849,7 @@ class InvoiceLine(sequence_ordered(), ModelSQL, ModelView, TaxableMixin):
             tax_line = TaxLine()
             tax_line.amount = amount
             tax_line.type = 'base'
-            tax_line.tax = tax['tax']
+            tax_line.tax = tax.tax
             tax_lines.append(tax_line)
         return tax_lines
 
@@ -3093,11 +3102,8 @@ class InvoiceTax(sequence_ordered(), ModelSQL, ModelView):
 
     @property
     def _key(self):
-        # Same as _TaxKey
-        tax_id = self.tax.id if getattr(self, 'tax', None) else -1
-        account_id = (
-            self.account.id if getattr(self, 'account', None) else None)
-        return (account_id, tax_id, (getattr(self, 'base', 0) or 0) >= 0)
+        # Same as _TaxLine
+        return (self.account, self.tax, (getattr(self, 'base', 0) or 0) >= 0)
 
     @classmethod
     def check_modification(cls, mode, taxes, values=None, external=False):
diff --git a/modules/account_tax_non_deductible/account.py b/modules/account_tax_non_deductible/account.py
index 376514ac50..e25f4217eb 100644
--- a/modules/account_tax_non_deductible/account.py
+++ b/modules/account_tax_non_deductible/account.py
@@ -48,7 +48,7 @@ class InvoiceLine(metaclass=PoolMeta):
                 with Transaction().set_context(
                         _non_deductible=True, _deductible_rate=1):
                     tax_amount = sum(
-                        t['amount'] for t in self._get_taxes().values())
+                        t.amount for t in self._get_taxes().values())
                 amount += tax_amount
         return amount
 
@@ -87,7 +87,7 @@ class InvoiceLine(metaclass=PoolMeta):
             taxes = self._get_taxes().values()
             for tax in taxes:
                 for type_, amount in [('base', 'base'), ('tax', 'amount')]:
-                    amount = tax[amount]
+                    amount = getattr(tax, amount)
                     with Transaction().set_context(
                             date=self.invoice.currency_date):
                         amount = Currency.compute(
@@ -96,6 +96,6 @@ class InvoiceLine(metaclass=PoolMeta):
                     tax_line = TaxLine()
                     tax_line.amount = amount
                     tax_line.type = type_
-                    tax_line.tax = tax['tax']
+                    tax_line.tax = tax.tax
                     tax_lines.append(tax_line)
         return tax_lines
diff --git a/modules/purchase/purchase.py b/modules/purchase/purchase.py
index 2fdabd99b0..0d4889daa8 100644
--- a/modules/purchase/purchase.py
+++ b/modules/purchase/purchase.py
@@ -527,8 +527,7 @@ class Purchase(
 
     @fields.depends(methods=['_get_taxes'])
     def get_tax_amount(self):
-        taxes = iter(self._get_taxes().values())
-        return sum((tax['amount'] for tax in taxes), Decimal(0))
+        return sum((t.amount for t in self._get_taxes().values()), Decimal(0))
 
     @classmethod
     def get_amount(cls, purchases, names):
diff --git a/modules/sale/sale.py b/modules/sale/sale.py
index d59961cbf0..780c1f14bb 100644
--- a/modules/sale/sale.py
+++ b/modules/sale/sale.py
@@ -647,8 +647,7 @@ class Sale(
 
     @fields.depends(methods=['_get_taxes'])
     def get_tax_amount(self):
-        return sum(
-            (v['amount'] for v in self._get_taxes().values()), Decimal(0))
+        return sum((t.amount for t in self._get_taxes().values()), Decimal(0))
 
     @classmethod
     def get_amount(cls, sales, names):
diff --git a/modules/sale_point/sale.py b/modules/sale_point/sale.py
index 14be9265e8..93a9486c9e 100644
--- a/modules/sale_point/sale.py
+++ b/modules/sale_point/sale.py
@@ -399,46 +399,45 @@ class POSSale(Workflow, ModelSQL, ModelView, TaxableMixin):
         TaxLine = pool.get('account.tax.line')
 
         lines = []
-        taxes = self._get_taxes()
+        taxes = self._get_taxes().values()
 
         # Distribute rounding error from tax computation
-        tax_amount = sum(t['amount'] for t in taxes)
+        tax_amount = sum(t.amount for t in taxes)
         difference = self.total_tax - tax_amount
         if difference:
             remaining = difference
             for tax in taxes:
-                if tax['amount']:
+                if tax.amount:
                     if tax_amount:
-                        ratio = tax['amount'] / tax_amount
+                        ratio = tax.amount / tax_amount
                     else:
                         ratio = 1 / len(taxes)
                     value = self.currency.round(difference * ratio)
-                    tax['amount'] += value
+                    tax.amount += value
                     remaining -= value
             # Add remaining rounding error to the first tax
             if remaining:
                 for tax in taxes:
-                    if tax['amount']:
-                        tax['amount'] += remaining
+                    if tax.amount:
+                        tax.amount += remaining
                         break
 
         for tax in taxes:
-            amount = tax['amount']
+            amount = tax.amount
             if not amount:
                 continue
             line = Line()
-            line.description = tax['description']
+            line.description = tax.tax.description
             if amount >= 0:
                 line.debit, line.credit = Decimal(0), amount
             else:
                 line.debit, line.credit = -amount, 0
-            line.account = tax['account']
-            if tax['tax']:
-                tax_line = TaxLine()
-                tax_line.amount = amount
-                tax_line.type = 'tax'
-                tax_line.tax = tax['tax']
-                line.tax_lines = [tax_line]
+            line.account = tax.account
+            tax_line = TaxLine()
+            tax_line.amount = amount
+            tax_line.type = 'tax'
+            tax_line.tax = tax.tax
+            line.tax_lines = [tax_line]
             lines.append(line)
         return lines
 
@@ -691,11 +690,11 @@ class POSSaleLine(ModelSQL, ModelView, TaxableMixin):
         line.origin = self
 
         tax_lines = []
-        for tax in self._get_taxes():
+        for tax in self._get_taxes().values():
             tax_line = TaxLine()
-            tax_line.amount = tax['base']
+            tax_line.amount = tax.base
             tax_line.type = 'base'
-            tax_line.tax = tax['tax']
+            tax_line.tax = tax.tax
             tax_lines.append(tax_line)
         line.tax_lines = tax_lines
         return [line]
diff --git a/modules/sale_shipment_cost/sale.py b/modules/sale_shipment_cost/sale.py
index 17db34e95d..c064acbe4b 100644
--- a/modules/sale_shipment_cost/sale.py
+++ b/modules/sale_shipment_cost/sale.py
@@ -517,7 +517,7 @@ class Promotion(metaclass=PoolMeta):
                 l.amount for l in sale.lines if l.shipment_cost is not None)
             if not self.untaxed_amount:
                 amount -= sum(
-                    v['amount']
+                    t.amount
                     for l in sale.lines if l.shipment_cost is not None
-                    for v in l._get_taxes().values())
+                    for t in l._get_taxes().values())
         return amount
diff --git a/modules/web_shop_vue_storefront/sale.py b/modules/web_shop_vue_storefront/sale.py
index 75240bc987..227e5ba962 100644
--- a/modules/web_shop_vue_storefront/sale.py
+++ b/modules/web_shop_vue_storefront/sale.py
@@ -179,8 +179,7 @@ class Line(metaclass=PoolMeta):
 
     @property
     def vsf_tax_amount(self):
-        return sum(
-            (v['amount'] for v in self._get_taxes().values()), Decimal(0))
+        return sum((t.amount for t in self._get_taxes().values()), Decimal(0))
 
     def get_vsf_user_order_history(self):
         amount_incl_tax = self.amount + self.vsf_tax_amount