Iowa Code § 74.2: Endorsement and interest.

1. If a warrant other than an anticipatory warrant is presented for payment, and is not paid for want of funds, or is only partially paid, the treasurer shall endorse the fact on the warrant, with the date of presentation, and sign the endorsement. After the date of presentation, the warrant or the balance due on the warrant shall bear interest at the rate specified in section 74A.2.

2. An anticipatory warrant issued under the authority of section 74.1, subsection 1, shall bear interest at a rate determined by the issuing governmental body, but not exceeding that permitted by chapter 74A.