law: The Integrated Goods and Services Tax Act, 2017
  21. Import of services made on or after the appointed day.-
  Import of services made on or after the appointed day shall be liable to tax under the provisions of this Act regardless of whether the transactions for such import of services had been initiated before the appointed day:
  Provided that if the tax on such import of services had been paid in full under the existing law, no tax shall be payable on such import under this Act:
  Provided further that if the tax on such import of services had been paid in part under the existing law, the balance amount of tax shall be payable on such import under this Act.
  Explanation.-For the purposes of this section, a transaction shall be deemed to have been initiated before the appointed day if either the invoice relating to such supply or payment, either in full or in part, has been received or made before the appointed day.