Tax collected but not paid triggers immediate payment obligation and recovery measures including interest and show cause proceedings. Persons who collect tax and do not remit it must forthwith pay the collected amount to the Government; the proper officer may serve a show cause notice, determine the amount due after considering representations, and require payment. Interest accrues from the date of collection until payment, a written request for hearing must be granted, and the officer must issue a reasoned order within one year, excluding judicial stays. Payments are adjusted against tax liability and any surplus is either credited to the Fund or refunded, with refund claims processed under the Act.