diff --git a/addons/account/account.py b/addons/account/account.py
index c45c337f019..2910d3d64a1 100644
--- a/addons/account/account.py
+++ b/addons/account/account.py
@@ -1949,15 +1949,15 @@ class account_tax(osv.osv):
         #
         'base_code_id': fields.many2one('account.tax.code', 'Account Base Code', help="Use this code for the tax declaration."),
         'tax_code_id': fields.many2one('account.tax.code', 'Account Tax Code', help="Use this code for the tax declaration."),
-        'base_sign': fields.float('Base Code Sign', help="Usually 1 or -1."),
-        'tax_sign': fields.float('Tax Code Sign', help="Usually 1 or -1."),
+        'base_sign': fields.float('Base Code Sign', help="Usually 1 or -1.", digits_compute=get_precision_tax()),
+        'tax_sign': fields.float('Tax Code Sign', help="Usually 1 or -1.", digits_compute=get_precision_tax()),
 
         # Same fields for refund invoices
 
         'ref_base_code_id': fields.many2one('account.tax.code', 'Refund Base Code', help="Use this code for the tax declaration."),
         'ref_tax_code_id': fields.many2one('account.tax.code', 'Refund Tax Code', help="Use this code for the tax declaration."),
-        'ref_base_sign': fields.float('Base Code Sign', help="Usually 1 or -1."),
-        'ref_tax_sign': fields.float('Tax Code Sign', help="Usually 1 or -1."),
+        'ref_base_sign': fields.float('Base Code Sign', help="Usually 1 or -1.", digits_compute=get_precision_tax()),
+        'ref_tax_sign': fields.float('Tax Code Sign', help="Usually 1 or -1.", digits_compute=get_precision_tax()),
         'include_base_amount': fields.boolean('Included in base amount', help="Indicates if the amount of tax must be included in the base amount for the computation of the next taxes"),
         'company_id': fields.many2one('res.company', 'Company', required=True),
         'description': fields.char('Tax Code'),