Section 12(2)(a) in The U.P. Goods and Services Tax Act, 2017
(a)the date of issue of invoice by the supplier or the last date on which he is required, under [***] [Omitted 'sub-section (1) of' by Uttar Pradesh Act No. 45 of 2018, dated 24.12.2018.] of section 31, to issue the invoice with respect to the supply; or