Every Person who is liable to be registered under Section 22 or Section 24 shall apply within 30 days from the date on which he becomes liable to registration in such manner and subject to such conditions as may be prescribed. Further, a casual taxable person or a non-resident taxable person shall apply for registration at least 5 days prior to the commencement of business. Furthermore, every person who makes a supply from the territorial waters of India shall obtain registration in the coastal State or Union territory where the nearest point of the appropriate baseline is located.
(ICAI FAQ PUBLICATIONS 06-09-2017 REGISTRATION: FAQ NO. 3)