Plan the set-off before filing so CGST and SGST balances stay equal.
IGST
CGST
SGST
1. Opening credit balance
2. Purchases this month (tax in GSTR-2B)
3. Tax on sales this month
Leave SGST blank when it is the same as CGST. For local sales only, IGST stays 0.
Result
Tax payable and how to pay it
IGST
CGST
SGST
How it is worked out: IGST credit pays IGST tax first. All remaining IGST credit is then used against CGST and SGST tax, split so the closing CGST and SGST balances are as equal as possible. CGST or SGST credit is used only after the IGST credit is finished. IGST credit left over means it was more than the total CGST and SGST tax. If you untick the box, the planner may keep some IGST unused to make CGST and SGST exactly equal. CGST credit pays CGST (then IGST) and SGST credit pays SGST (then IGST); they never pay each other. If the balances cannot be made equal, the planner gets them as close as possible. Estimate only: enter the split in the tax payment table of your GSTR-3B and check it on the GST portal before filing.