At the close of each school year the board of directors in each school district shall cause a complete settlement to be made with each depository agent. A complete inventory of the textbooks on hand, with a statement itemized to show the expenses authorized and paid by the board, and the amount of money collected from each such depository agent during the year from the sale or rental of textbooks, shall be made in duplicate, signed by the secretary of the board and the depository agent and one copy filed with the secretary and one with the depository agent.
Iowa Code § 301.3