diff --git a/invoice.py b/invoice.py
index 4056cad4fa..39b01d48b2 100644
--- a/invoice.py
+++ b/invoice.py
@@ -11,7 +11,8 @@ from sql.aggregate import Count, Sum
 from sql.conditionals import Coalesce, Case
 from sql.functions import Round
 
-from trytond.model import Workflow, ModelView, ModelSQL, fields, Check
+from trytond.model import Workflow, ModelView, ModelSQL, fields, Check, \
+    sequence_ordered
 from trytond.report import Report
 from trytond.wizard import Wizard, StateView, StateTransition, StateAction, \
     StateReport, Button
@@ -1365,7 +1366,7 @@ class InvoicePaymentLine(ModelSQL):
             ondelete='CASCADE', select=True, required=True)
 
 
-class InvoiceLine(ModelSQL, ModelView, TaxableMixin):
+class InvoiceLine(sequence_ordered(), ModelSQL, ModelView, TaxableMixin):
     'Invoice Line'
     __name__ = 'account.invoice.line'
     _rec_name = 'description'
@@ -1412,10 +1413,6 @@ class InvoiceLine(ModelSQL, ModelView, TaxableMixin):
             ('id', If(Eval('context', {}).contains('company'), '=', '!='),
                 Eval('context', {}).get('company', -1)),
             ], select=True, states=_states, depends=_depends)
-    sequence = fields.Integer('Sequence',
-        states={
-            'invisible': Bool(Eval('context', {}).get('standalone')),
-            })
     type = fields.Selection([
         ('line', 'Line'),
         ('subtotal', 'Subtotal'),
@@ -1524,7 +1521,6 @@ class InvoiceLine(ModelSQL, ModelView, TaxableMixin):
                     | (t.type == 'line')),
                 'Line without "line" type must have an invoice.'),
             ]
-        cls._order.insert(0, ('sequence', 'ASC'))
         cls._error_messages.update({
                 'modify': ('You can not modify line "%(line)s" from invoice '
                     '"%(invoice)s" that is posted or paid.'),
@@ -1557,6 +1553,9 @@ class InvoiceLine(ModelSQL, ModelView, TaxableMixin):
                             + cls._account_domain('in'))))),
             ]
         cls.account.depends += ['company', 'invoice_type']
+        cls.sequence.states.update({
+                'invisible': Bool(Eval('context', {}).get('standalone')),
+                })
 
     @staticmethod
     def _account_domain(type_):
@@ -1591,11 +1590,6 @@ class InvoiceLine(ModelSQL, ModelView, TaxableMixin):
             cursor.execute(*sql_table.update([sql_table.company], [company_id],
                     where=sql_table.id == line_id))
 
-    @staticmethod
-    def order_sequence(tables):
-        table, _ = tables[None]
-        return [Case((table.sequence == Null, 0), else_=1), table.sequence]
-
     @staticmethod
     def default_currency():
         Company = Pool().get('company.company')
@@ -2002,7 +1996,7 @@ class InvoiceLineTax(ModelSQL):
             required=True)
 
 
-class InvoiceTax(ModelSQL, ModelView):
+class InvoiceTax(sequence_ordered(), ModelSQL, ModelView):
     'Invoice Tax'
     __name__ = 'account.invoice.tax'
     _rec_name = 'description'
@@ -2021,7 +2015,6 @@ class InvoiceTax(ModelSQL, ModelView):
         'on_change_with_invoice_state')
     description = fields.Char('Description', size=None, required=True,
         states=_states, depends=_depends)
-    sequence = fields.Integer('Sequence')
     sequence_number = fields.Function(fields.Integer('Sequence Number'),
             'get_sequence_number')
     account = fields.Many2One('account.account', 'Account', required=True,
@@ -2067,7 +2060,6 @@ class InvoiceTax(ModelSQL, ModelView):
     @classmethod
     def __setup__(cls):
         super(InvoiceTax, cls).__setup__()
-        cls._order.insert(0, ('sequence', 'ASC'))
         cls._error_messages.update({
                 'modify': ('You can not modify tax "%(tax)s" from invoice '
                     '"%(invoice)s" because it is posted or paid.'),
@@ -2093,11 +2085,6 @@ class InvoiceTax(ModelSQL, ModelView):
         # Migration from 2.4: drop required on sequence
         table.not_null_action('sequence', action='remove')
 
-    @staticmethod
-    def order_sequence(tables):
-        table, _ = tables[None]
-        return [Case((table.sequence == Null, 0), else_=1), table.sequence]
-
     @staticmethod
     def default_base():
         return Decimal('0.0')
diff --git a/payment_term.py b/payment_term.py
index 979dcd9fda..2cdd6ce133 100644
--- a/payment_term.py
+++ b/payment_term.py
@@ -3,10 +3,9 @@
 from decimal import Decimal
 from dateutil.relativedelta import relativedelta
 
-from sql import Null, Column
-from sql.conditionals import Case
+from sql import Column
 
-from trytond.model import ModelView, ModelSQL, fields
+from trytond.model import ModelView, ModelSQL, fields, sequence_ordered
 from trytond import backend
 from trytond.pyson import Eval
 from trytond.transaction import Transaction
@@ -98,11 +97,9 @@ class PaymentTerm(ModelSQL, ModelView):
         return res
 
 
-class PaymentTermLine(ModelSQL, ModelView):
+class PaymentTermLine(sequence_ordered(), ModelSQL, ModelView):
     'Payment Term Line'
     __name__ = 'account.invoice.payment_term.line'
-    sequence = fields.Integer('Sequence',
-        help='Use to order lines in ascending order')
     payment = fields.Many2One('account.invoice.payment_term', 'Payment Term',
             required=True, ondelete="CASCADE")
     type = fields.Selection([
@@ -139,7 +136,6 @@ class PaymentTermLine(ModelSQL, ModelView):
     @classmethod
     def __setup__(cls):
         super(PaymentTermLine, cls).__setup__()
-        cls._order.insert(0, ('sequence', 'ASC'))
         cls._error_messages.update({
                 'invalid_ratio_and_divisor': ('Ratio and '
                     'Divisor values are not consistent in line "%(line)s" '
@@ -186,11 +182,6 @@ class PaymentTermLine(ModelSQL, ModelView):
                     values=[sql_table.percentage / 100]))
             table.drop_column('percentage')
 
-    @staticmethod
-    def order_sequence(tables):
-        table, _ = tables[None]
-        return [Case((table.sequence == Null, 0), else_=1), table.sequence]
-
     @staticmethod
     def default_currency_digits():
         return 2
@@ -291,10 +282,9 @@ class PaymentTermLine(ModelSQL, ModelView):
                         })
 
 
-class PaymentTermLineRelativeDelta(ModelSQL, ModelView):
+class PaymentTermLineRelativeDelta(sequence_ordered(), ModelSQL, ModelView):
     'Payment Term Line Relative Delta'
     __name__ = 'account.invoice.payment_term.line.delta'
-    sequence = fields.Integer('Sequence')
     line = fields.Many2One('account.invoice.payment_term.line',
         'Payment Term Line', required=True, ondelete='CASCADE')
     day = fields.Integer('Day of Month',
@@ -331,11 +321,6 @@ class PaymentTermLineRelativeDelta(ModelSQL, ModelView):
     weeks = fields.Integer('Number of Weeks', required=True)
     days = fields.Integer('Number of Days', required=True)
 
-    @classmethod
-    def __setup__(cls):
-        super(PaymentTermLineRelativeDelta, cls).__setup__()
-        cls._order.insert(0, ('sequence', 'ASC'))
-
     @classmethod
     def __register__(cls, module_name):
         TableHandler = backend.get('TableHandler')
@@ -368,11 +353,6 @@ class PaymentTermLineRelativeDelta(ModelSQL, ModelView):
             for field in fields:
                 line_table.drop_column(field, exception=True)
 
-    @staticmethod
-    def order_sequence(tables):
-        table, _ = tables[None]
-        return [Case((table.sequence == Null, 0), else_=1), table.sequence]
-
     @staticmethod
     def default_months():
         return 0