Change fiscal positon for export 0% vat

If you want to overwrite the vat you have to delete one line in the file account/partner.py

def map_tax(self, cr, uid, fposition_id, taxes, context={}):
        if not taxes:
            return []
        if not fposition_id:
            return map(lambda x: x.id, taxes)
        result = []
        for t in taxes:
            ok = False
            for tax in fposition_id.tax_ids:
#comment the following line out!
#                if tax.tax_src_id.id == t.id:
                    print tax.tax_src_id
                    print tax.tax_dest_id
                    if tax.tax_dest_id:
                        result.append(tax.tax_dest_id.id)
                    ok=True
            if not ok:
                result.append(t.id)
        return result