Iowa Code § 468.68
Warrants drawn upon the construction or maintenance funds of any district for which an assessment has been or must be levied, shall be transferable by endorsement, and may be acquired by any taxpayer of such district and applied at their accrued face value upon the assessment levied to create the fund against which the warrant was drawn; when the amount of the warrant exceeds the amount of the assessment, the treasurer shall cancel the warrant, and give the holder thereof a certificate for the amount of such excess, which certificate shall be filed with the auditor, who shall issue a warrant for the amount of such excess, and charge the treasurer therewith. Such certificate is transferable by endorsement, and will entitle the holder to the new warrant, made payable to the holder's order, and bearing the original number, preceded by the following words:
Issued as unpaid balance due on warrant number .................
Iowa Code § 468.68
89 Acts, ch 126, §2 2018 Acts, ch 1041, § 98