Tax collected but not paid: immediate payment to government required, with interest and potential penalty after notice. Every person who collects any amount as tax under this Act and does not remit that amount to the Government must forthwith pay the amount to the Government regardless of whether the supplies are taxable. The proper officer may issue a show cause notice, determine the amount due after representation, and the person must pay the determined amount with interest from the date of collection; a hearing may be requested in writing, the officer must issue a reasoned order within one year (excluding stays), and amounts paid are adjusted against tax payable with any surplus credited or refunded under the Act.