Unsure whether the invoice should carry IGST or CGST + SGST in the first place? Run the place of supply determiner.
Two provisions share the same calendar. Section 34(2) of the CGST Act requires a supplier who issues a credit note to declare it in a return no later than 30 November following the end of the financial year in which the SUPPLY was made, or the date of filing the annual return (GSTR-9) for that year, whichever is earlier. Section 16(4) bars a recipient from taking input tax credit on an invoice or debit note after 30 November following the end of the financial year to which the invoice or debit note pertains, or the date of filing the annual return, whichever is earlier. Both dates were moved from "the September return" to 30 November by the Finance Act 2022, effective 1 October 2022, applicable from FY 2021-22 onwards.
The Finance (No. 2) Act 2024 then added two retrospective relaxations (both deemed effective from 1 July 2017, notified on 27 September 2024). Section 16(5): for invoices and debit notes of FY 2017-18, 2018-19, 2019-20 and 2020-21, ITC availed in any GSTR-3B filed up to 30 November 2021 is treated as within time — validating lakhs of late claims that had been demanded back under Section 16(4). Section 16(6): where a registration was cancelled and later revoked, ITC can be taken up to the normal deadline OR in the return for the cancellation-to-revocation period filed within 30 days of the revocation order, whichever is LATER — provided the credit was not already time-barred on the date of the cancellation order. CBIC operationalised both through Circular 237/31/2024-GST and a special rectification procedure under Notification 22/2024-Central Tax.
One more layer arrived with the Finance Act 2025 (effective 1 October 2025): a supplier can reduce output tax through a credit note only if the recipient has reversed the corresponding ITC (or the tax incidence was not passed on) — enforced through the Invoice Management System (IMS). And on the recipient's side, Rule 37 (non-payment to the supplier within 180 days) and Rule 37A (supplier fails to file GSTR-3B by 30 September following the FY — recipient must reverse by 30 November) create reversal obligations whose RE-availment, importantly, is not blocked by the Section 16(4) clock.
A supplier discovers in July 2026 that goods invoiced in January 2026 (FY 2025-26) were partly returned, and the buyer separately finds an unclaimed purchase invoice of the same year. Neither has filed GSTR-9 for FY 2025-26 yet.