diff --git a/addons/account/account_invoice.py b/addons/account/account_invoice.py
index f90c9661c09..7b5d8b818a0 100644
--- a/addons/account/account_invoice.py
+++ b/addons/account/account_invoice.py
@@ -1696,13 +1696,10 @@ class account_invoice_tax(osv.osv):
         cur_obj = self.pool.get('res.currency')
         company_obj = self.pool.get('res.company')
         company_currency = False
-        factor = 1
-        if ids:
-            factor = self.read(cr, uid, ids[0], ['factor_tax'])['factor_tax']
         if company_id:
             company_currency = company_obj.read(cr, uid, [company_id], ['currency_id'])[0]['currency_id'][0]
         if currency_id and company_currency:
-            amount = cur_obj.compute(cr, uid, currency_id, company_currency, amount*factor, context={'date': date_invoice or fields.date.context_today(self, cr, uid)}, round=False)
+            amount = cur_obj.compute(cr, uid, currency_id, company_currency, amount, context={'date': date_invoice or fields.date.context_today(self, cr, uid)}, round=False)
         return {'value': {'tax_amount': amount}}
 
     _order = 'sequence'