Interest on delayed payment of duty accrues at government fixed rates from duty due date until actual payment is made. Interest is chargeable on delayed payment of central excise duty in addition to the duty itself, applying whether payment is voluntary or follows a determination; the Central Government fixes a rate within a prescribed band by notification and interest is calculated from the date the duty becomes due until actual payment, subject to a narrow exception where duty arising from a Board order is paid in full within forty five days without reserving appeal rights.