Iowa Code § 633.418

No claim shall be allowed against an estate on application of the claimant unless it shall be in writing, filed with the clerk, stating the claimant’s name and address and, if available, telephone number and electronic mail address, describing the nature and the amount thereof, if ascertainable, and accompanied by the affidavit of the claimant, or someone for the claimant, that the amount is justly due, or if not yet due, when it will or may become due, that no payments have been made thereon which are not credited, and that there are no offsets to the same, to the knowledge of the affiant, except as therein stated. If the claim is contingent, the nature of the contingency shall also be stated.