Iowa Code § 182.15: Invoice required.

1. At the time of sale, the first purchaser shall sign and deliver to the producer separate invoices for each purchase. The invoices shall show:

a. The name and address of the producer and the seller, if different from the producer.

b. The name and address of the first purchaser.

c. The pounds of wool or head of sheep sold.

d. The date of the purchase.

e. The rate of withholding and the total amount of the assessment withheld.

2. Invoices shall be legibly written and shall not be altered.