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GSTR-1 reports your outward supplies (sales). GSTR-3B is a summary return where you declare sales, claim ITC and pay tax. The two must reconcile.
| GSTR-1 | GSTR-3B | |
|---|---|---|
| Reports | Invoice-wise sales | Summary of sales, ITC, tax paid |
| Due (monthly) | 11th | 20th |
| Feeds | Buyers' GSTR-2B | Cash/credit ledger |
How a mismatch arises
- Sales in GSTR-1 not included in GSTR-3B (or vice versa)
- Credit notes accounted in one return only
- Amendments in later periods
Fix it
- Reconcile both with your books every month.
- Correct differences in the next return through amendment tables.
- Keep working papers for notices.
See the due date pages: GSTR-1 and GSTR-3B.
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General information only; not professional advice. Rates, limits and due dates change. Verify with official sources or consult a professional. Reviewed October 2026. See our editorial policy.
