Tax collected but not paid - liable to immediate payment with interest, show cause proceedings and adjustment or refund. Section 76 requires any person who collected amounts as tax and has not paid them to the Government to immediately remit those amounts, regardless of taxability of supplies. The proper officer may issue a show cause notice proposing payment and a penalty, determine the amount after considering representations, and require payment. Interest accrues from collection to payment. Orders must state facts and reasons and be issued within one year (excluding periods of judicial stay). Payments are adjusted against tax payable and any surplus credited to the Fund or refunded under the Act's refund procedure.