Generally, in terms of Section 12 of the CGST Act, 2017, the time of supply of goods shall be the earliest of the following:
(a) Date of issue of invoice; or
(b) Due date of issue of invoice; or
(c) Date on which payment is entered in books of accounts of the supplier; or
(d) Date on which payment is credited to the bank account.
(ICAI FAQ PUBLICATIONS 06-09-2017 TIME OF SUPPLY OF GOODS : FAQ NO 2)