Any credits accumulated from a tax filing will be carried forward unless a refund is requested. Any overpayment will be processed as a credit if the refund box is not marked.  If you would like a refund for accumulated IFTA credits a signed letter, on company letterhead, requesting the full credit amount must be mailed. Any credits under $100.00 will not be refunded and will be forwarded as a credit. IFTA credits if not refunded can only be used to pay IFTA quarterly tax returns.