The only thing I've seen is 537.3206(3) which states "After a consumer has fulfilled all obligations with respect to a consumer credit transaction, other than one pursuant to open end credit, the person to whom the obligation was owed shall, upon request of the consumer, deliver or mail to the consumer written evidence acknowledging payment in full of all obligations with respect to the transaction."
There may be something more specific on this that I haven't seen.
Rant warning: I think the search feature on the Iowa General Assembly website is horrible. You will rarely find what you are looking for unless you already know where to find it. Not very helpful.
