Section 13(2)(a) in The Central Goods and Services Tax Act, 2017
(a)the date of issue of invoice by the supplier, if the invoice is issued within the period prescribed under [OMIT] [Omitted 'sub-section (2) of' by Act No. 31 of 2018, dated 29.8.2018.] section 31 or the date of receipt of payment, whichever is earlier; or