A registered taxable person supplying services, in terms of Section 31(2) of the CGST Act, 2017, shall issue the tax invoice before or after the provision of service but within a period prescribed in this behalf. Accordingly, the last date within which the invoice should be issued will be the ‘due date of issuance of invoice’. As per Rule 47 of the CGST Rules, 2017 the time limit for issuing a tax invoice is thirty days from the date of provision of service.
(ICAI FAQ PUBLICATION 06-09-2017 : Time and Value of Supply -FAQ NO. 22)