Application for registration of authorised income-tax practitioners requires prescribed form, eligibility proof, and jurisdictional filing. Application for registration as an authorised income-tax practitioner must be made to the jurisdictional Chief Commissioner or Commissioner in Form No. 171, supported by documentary evidence of eligibility and any further information required. A person already registered under the repealed Income-tax Act, 1961, with a valid certificate on 31 March 2026, continues as a registered income-tax practitioner under section 515, but must update details by filing the prescribed application by 30 September 2026.