law: The Central Goods and Services Tax Act, 2017
  27. Special provisions relating to casual taxable person and non-resident taxable person.-
  (1) The certificate of registration issued to a casual taxable person or a non-resident taxable person shall be valid for the period specified in the application for registration or ninety days from the effective date of registration, whichever is earlier and such person shall make taxable supplies only after the issuance of the certificate of registration:
  Provided that the proper officer may, on sufficient cause being shown by the said taxable person, extend the said period of ninety days by a further period not exceeding ninety days.
  (2) A casual taxable person or a non-resident taxable person shall, at the time of submission of application for registration under sub-section (1) of section 25, make an advance deposit of tax in an amount equivalent to the estimated tax liability of such person for the period for which the registration is sought:
  Provided that where any extension of time is sought under sub-section (1), such taxable person shall deposit an additional amount of tax equivalent to the estimated tax liability of such person for the period for which the extension is sought.
  (3) The amount deposited under sub-section (2) shall be credited to the electronic cash ledger of such person and shall be utilised in the manner provided under section 49.