The biggest question to answer when it comes to operating in other states is to determine if you’re “doing business” in another state. In general, if you’re “on the ground” in another state providing a service or selling your product, you probably have a business presence in that state.
From the Archives: How to Allocate the Deduction for Federal Estimated Tax Payments on Your Iowa Tax Return
Iowa allows a deduction for federal income taxes paid, including estimated tax payments. The deduction for estimated payments is not straightforward if you're filing your tax return as married filing separately.
If you worked in more than one state, you might have a filing obligation in the state where you’re a resident, and in the state you worked in.
How to calculate taxation of federal refund on Iowa tax return