495—4.4 (97B) Accrual of interest and application of employer payments. Interest or charges as provided under Iowa Code section 97B.9 shall accrue on all employer payments not received by IPERS by the due date, except that interest or charges may be waived by IPERS if the employer requests an extension of time under subrule 4.3(4) prior to the due date. Effective August 1, 2008, employers that remit late contributions shall be charged a minimum of $20 or interest at the rate provided in Iowa Code section 97B.70, whichever is greater. No fee will be charged on late contributions received as a result of a wage adjustment, but interest on the amount due will be charged until paid in full. Payments received from employers having unpaid account balances shall first be applied to the oldest outstanding balance.