Income tax returns are due on April 30 following the tax year. If the due date falls on a Saturday, Sunday, or holiday as defined in Iowa code 421.9A, then the due date is the following day that is not a Saturday, Sunday, or holiday.
Iowa has no paper extension form. If you have at least 90% of the tax paid by the due date, you will automatically have until October 31 to file the return.
If an additional payment is necessary in order to meet the 90% requirement, you must make payment using the Iowa Individual Income Tax Payment Voucher (96-048). Vouchers can be found in the Tax Forms Index by choosing the Individual Income tax type. If 90% of the correct tax is not paid timely, penalty, and interest apply.
Interest will accrue on any tax not paid by the original due date.