You get an extra 180 days to file your Iowa income tax return after you return from a combat zone, or after you are released from hospital treatment for injuries you received in a combat zone.
There is nothing to file in advance. File your Iowa return within 180 days of returning from the combat zone or being released from hospitalization, and tell the Iowa Department of Revenue that the extension applies to you if they contact you about a late return.
Your orders showing the combat zone service dates, or hospital paperwork for injuries received in a combat zone.