The Department shall pay all refunds due under this Act within 90 days after receipt of application for a refund. For commercial motor vehicles, refunds paid after the expiration of the 90 day period shall bear interest at the rate of 1% per month or fraction of a month. Refunds paid to all other persons subject to this Act shall be paid at the rate and in the manner set by the Uniform Penalty and Interest Act.
35 ILCS 505/15.1