Failure to deduct or collect tax triggers deemed assessee status with interest and asset charge unless payee files return. Failure to deduct, collect or pay tax at source makes the person a deemed assessee in default, subject to liability for prescribed simple interest for the periods before and after deduction/collection, unless the payee/buyer/licensee/lessee has filed a return declaring the amount and paid tax and the person furnishes an accountant's certificate; unpaid tax and interest form a charge on the person's assets, orders are subject to specified limitation periods, and penalties require proof of lack of good and sufficient reasons.