Iowa Code § 422.91 — Credit for estimated tax

1. Any amount of estimated tax paid is a credit against the amount of tax due on a final, completed return, and any overpayment of five dollars or more shall be refunded to the taxpayer with interest in accordance with section 421.60, subsection 2 , paragraph “e” , and the return constitutes a claim for refund for this purpose. Amounts less than five dollars shall be refunded to the taxpayer only upon written application in accordance with section 422.73 , and only if the application is filed within twelve months after the due date for the return. 2. In lieu of claiming a refund, the taxpayer may elect to have the overpayment shown on its final, completed return for the taxable year credited to the tax liability for the following taxable year .