confugation: add 'accept_incomplete_tax'

configuration.py

@@ -25,6 +25,9 @@ class Configuration(metaclass=PoolMeta):
         string='Accept other company',
         help='Accepts invoices created for a company other ' +
         'than the current one.')
+    accept_incomplete_tax = fields.Boolean(
+        string='Incomplete tax data',
+        help='Accepts incomplete data in the taxes of invoice lines.')
     number_target = fields.Selection(
         string='Invoice number',
         help='Destination for the invoice number of the supplier invoice.',
@@ -35,6 +38,15 @@ class Configuration(metaclass=PoolMeta):
         'on an invoice line.',
         relation_name='document.incoming.confprodcat_rel')
 
+    @classmethod
+    def default_accept_incomplete_tax(cls):
+        """ allow tax on invoice-line by percent, without 'VAT'-type
+
+        Returns:
+            bool: True
+        """
+        return True
+
     @classmethod
     def default_number_target(cls):
         """ targetfield for incoming invoice number