Tax collected but not paid must be remitted and may attract notice, penalty and interest; adjustment or refund mechanisms follow. Section 76 requires any person who collected amounts as tax under the Act and has not paid them to remit those amounts forthwith regardless of supply taxability. The proper officer may issue a show cause notice, determine the due amount after considering representations, and require payment; interest under section 50 applies from collection to payment. A written request entitles the person to a hearing, the officer must issue an order within one year (excluding stays) and state reasons. Payments are adjustable against tax liability; any surplus is credited to the Fund or refunded to the person who bore the incidence under section 54.