Iowa Code § 432A.8: Filing tax return.

Every insurer liable to pay the tax shall, on or before June 1 of each year, file with the commissioner of insurance a tax return in accordance with or upon forms prescribed by the commissioner of insurance. The tax shown to be due, if any, shall be paid to the director of revenue who shall issue to the insurer a receipt in duplicate, one of which shall be filed with the commissioner of insurance before issuance of the annual certificate as provided by law.