Two returns, two different jobs
Every regular GST-registered business files (at least) two returns for each tax period. GSTR-1 is a statement of outward supplies — a detailed, invoice-level list of everything you sold. GSTR-3B is a summary self-assessment return — total sales, total tax, total input tax credit claimed, and the net amount you actually pay. GSTR-1 carries information; GSTR-3B carries money.
If you want the full picture of the return calendar first, see our GST returns overview.
Side-by-side comparison
| GSTR-1 | GSTR-3B | |
|---|---|---|
| What it is | Invoice-wise statement of outward supplies (sales) | Summary return of sales, ITC and tax payment |
| Level of detail | Every B2B invoice with buyer GSTIN, rate, value; B2C in summary | Consolidated totals only — no invoice details |
| Tax paid with it? | No — purely informational | Yes — tax liability is discharged here |
| Typical due date | 11th of the following month (quarterly under QRMP for smaller taxpayers) | 20th of the following month (staggered dates for QRMP) |
| Who consumes the data | Your buyers — it populates their GSTR-2A/2B for ITC | The government — revenue collection |
| ITC involved? | No | Yes — you claim eligible ITC and pay the balance in cash |
Due-date patterns are long-standing but do get staggered and revised — verify current dates for your state and turnover on gst.gov.in.
How the two returns connect
Think of it as a relay:
- You file GSTR-1 listing, say, 40 sales invoices totalling ₹10,00,000 taxable value + ₹1,80,000 GST.
- The portal auto-drafts your GSTR-3B liability from that GSTR-1 data.
- Each B2B invoice you reported lands in your buyer's GSTR-2B, letting them claim ₹ of input tax credit — the flow we explain in GSTR-2B reconciliation.
- In GSTR-3B you set off your own eligible ITC (say ₹1,20,000) and pay the balance ₹60,000 in cash.
Because GSTR-1 feeds GSTR-3B, the system expects the two to agree. The portal compares the liability you declared in GSTR-1 with the tax you actually paid in GSTR-3B — and flags gaps.
What happens when GSTR-1 and GSTR-3B don't match
Small timing differences happen to everyone — an invoice reported in GSTR-1 for March but paid via 3B in April. Persistent or large gaps are a different story:
- Automated intimation: the portal can issue a notice (Form DRC-01B and similar mechanisms) asking you to explain why GSTR-1 liability exceeds GSTR-3B payment, or pay the difference with interest.
- Blocked filings: unresolved differences can block your subsequent GSTR-1 until you respond.
- Interest exposure: tax declared in GSTR-1 but paid late through 3B attracts interest on the shortfall for the delay period.
- Buyer-side pain: if you report an invoice in GSTR-1 but never pay the tax in 3B, the department can pursue you — and in some situations your buyer's credit comes under question, souring the relationship.
Concrete example: Meena's boutique reports ₹2,00,000 of GST liability in GSTR-1 for June but, short of cash, files GSTR-3B showing only ₹1,50,000. The ₹50,000 gap is visible to the system immediately. She will likely receive an intimation to pay ₹50,000 plus interest at the notified rate (long-standing rate: 18% per annum, counted day-wise) — roughly ₹25 per day on that shortfall until she pays.
Common causes of mismatch — and the fixes
- Invoices added in GSTR-1 after 3B was filed. Fix: pay the differential tax in the next 3B with interest; do not just ignore it.
- Credit notes reported in one return but not adjusted in the other. Fix: pass credit notes through your books once, and let both returns pick them up from the same source.
- B2C sales edited in GSTR-1 but 3B filed from an old draft. Fix: always regenerate 3B figures after finalising GSTR-1.
- Amendments in later months that shift values between periods. Fix: keep a simple month-wise reconciliation sheet — GSTR-1 liability vs 3B paid — so cumulative figures always tie out by year-end (this also makes GSTR-9 painless).
The discipline that keeps you notice-free
- Single source of truth: both returns should be generated from the same sales register, never typed independently.
- File GSTR-1 first, then 3B — in that order, every month, so the auto-drafted liability matches what you pay.
- Reconcile monthly, not yearly. A ₹10,000 gap found in the same month is a five-minute fix; found ten months later it comes with interest and a notice.
For step-by-step filing walkthroughs, see the detailed guides on GSTR-1 filing and GSTR-3B filing. And if you use iAccounting, the software builds both returns from the same invoice data automatically — see how to file GSTR-1 from iAccounting and how to file GSTR-3B.