18 October 2025
To correct the GST for the August 2025 invoice where CGST/SGST was charged instead of IGST—and GSTR-1 was already filed—you need to amend the invoice and update the GSTR-1 return as per GST law. Amendments are allowed until November 30, 2026, or before filing the annual return for FY 2025-26, whichever is earlier.
18 October 2025
Make sure to pay the IGST liability for the corrected invoice and adjust the wrongly paid CGST+SGST accordingly. You can claim a refund for the CGST/SGST paid.
Corrections in GSTR-1 will flow to the recipient’s GSTR-2A and impact the Input Tax Credit if applicable.
No interest or penalty applies if you pay the correct tax under genuine mistake, as per current GST Council guidelines.