Section 5(1)(b) in The Punjab Passengers and Goods Taxation Rules, 1952
(b)discontinues such business he shall, within thirty days of such sale, disposal, discontinuance or change, submit a report to that effect to the Assessing Authority, and if the owner is registered under the Act, he shall apply in form PTT 3 to the Assessing Authority for cancellation or amendment of the certificate of registration, as the case may be.