one of the my client (proprietor) had already cancelled their service tax no. (after payment of all dues) , however he had collected some payment in relation to service already provided , now quetion is that under which no. he should require to make payment of service tax .
Rule 4(7) of the Service tax rules, 1994 states that every assessee should surrender his certificate once he ceases to provide taxable services.
Rule 4(8) states that the Superintendent of Central Excise should ensure that all dues to the Central Government are paid before surrendering of the certificate.
In your specific case Rule 4(8) seem to have been violated. I would advise that you make a letter to the Superintendent of Central Excise stating the reasons for non payment and subsequent collections and then pay the relevant service tax.