Interest on refunds entitles assessees to simple interest for delayed refunds, with additional interest for post-order refunds. Interest is payable in addition to refunds, calculated as simple interest for specified circumstances with distinct commencement rules depending on the source of tax or refund trigger. Additional interest at a separate rate applies where refunds result from giving effect to specified orders without fresh assessment, excluding periods attributable to the assessee or where reassessment proceedings are pending. The provision caps interest entitlement below a specified refund threshold, grants similar interest rights to deductors, and provides for adjustment and demand notices where interest is later increased or reduced.