Every regular GST taxpayer files two core returns for each tax period: GSTR-1 and GSTR-3B. They are often mentioned together, but they serve different purposes — and the GST system cross-checks one against the other. Getting the relationship right is the simplest way to avoid mismatches, interest and notices.
What is GSTR-1?
GSTR-1 is a statement of outward supplies. It reports the details of the sales you made during the period, so that the tax you charged can be passed on to your customers’ records.
- Invoice-wise details of B2B supplies, with the recipient’s GSTIN
- B2C supplies, reported in summary (large inter-state B2C invoices in more detail)
- Credit notes and debit notes issued during the period
- Exports, supplies to SEZs and deemed exports
- An HSN-wise summary of outward supplies and a document summary
The B2B details you report in GSTR-1 flow into your customers’ auto-drafted statement GSTR-2B. That is how their input tax credit is determined — so late or incorrect GSTR-1 filing directly affects your customers.
What is GSTR-3B?
GSTR-3B is a summary return. Instead of invoice-level detail, it captures totals: your outward tax liability, the input tax credit you are claiming and the net tax you pay in cash. Tax is actually paid through GSTR-3B, which makes it the return that settles your liability for the period.
GSTR-1 vs GSTR-3B at a glance
| GSTR-1 | GSTR-3B | |
|---|---|---|
| Purpose | Statement of outward supplies | Summary return and tax payment |
| Level of detail | Invoice-wise (B2B) and summaries | Consolidated totals only |
| Tax payment | No | Yes — tax is paid with this return |
| Input tax credit | Not claimed here | Claimed here |
| Monthly due date | 11th of the next month | 20th of the next month |
| Quarterly (QRMP) due date | 13th of the month after the quarter | 22nd or 24th of the month after the quarter, depending on your state |
| Effect on others | Feeds your customers’ GSTR-2B | Does not flow to customers |
Taxpayers under the QRMP scheme can upload B2B invoices for the first two months of a quarter through the optional Invoice Furnishing Facility (IFF), due by the 13th of the following month, so their customers can claim credit without waiting for the quarter to end.
Why GSTR-1 and GSTR-3B must match
The liability you declare in GSTR-1 should equal the liability you discharge in GSTR-3B for the same period. When the system finds that GSTR-1 shows more tax than GSTR-3B, it can issue an intimation (Form DRC-01B) asking you to pay the difference or explain it. Differences also lead to interest on short-paid tax and questions during assessments and audits.
If you notice an error in GSTR-1 after filing it, you can correct it through GSTR-1A before filing GSTR-3B for that period, so the summary return reflects the corrected figures.
Practical tips for error-free filing
- File GSTR-1 first, then GSTR-3B — the portal pre-fills GSTR-3B liability from GSTR-1.
- Reconcile your sales register with GSTR-1 before filing, including credit and debit notes.
- Reconcile purchase records with GSTR-2B before claiming input tax credit in GSTR-3B.
- Verify each customer’s GSTIN so their credit is not blocked.
- Keep HSN codes and tax rates consistent between invoices and returns.