Unless the expense was incurred by the use of a purchasing card, before an allowance for mileage or travel expense may be paid by a county, the individual for whose travel the claim is made shall file with the county auditor an itemized statement verified by affidavit showing the number of miles traveled, the mode of travel, the days of traveling, the purpose of the travel, and the destination. Before a claim for mileage is allowed or paid, the claimant shall file the    statement and affidavit with the board of county commissioners which shall decide whether to allow the claim.