How to File GSTR-3B: Step-by-Step Guide for 2026

If you're a GST-registered business in India, you've probably spent a few stressful evenings rushing to file GSTR-3B before the 20th. You're not alone — this is the single most-filed GST return in the country, and getting it wrong can cost you real money.

This guide walks you through every step — from gathering data to hitting "submit" — so you can file with confidence.

What exactly is GSTR-3B?

Think of it as a monthly snapshot of your GST activity. Unlike GSTR-1 (which lists every invoice), GSTR-3B is a consolidated summary. You tell the government: here's how much I sold, how much tax I collected, how much ITC I'm claiming, and here's the net amount I owe.

Simple enough on paper. The tricky part is getting the numbers right — especially the ITC reconciliation with GSTR-2B.

Who needs to file?

• All regular GST-registered businesses — monthly filers
• QRMP scheme taxpayers — file quarterly, but pay tax monthly via PMT-06

Due dates for 2026

Monthly filers submit GSTR-3B by the 20th of the following month. So March 2026 is due by April 20th. QRMP quarterly filers have staggered dates — check your exact deadline on our free GST calendar.

Step-by-step filing process

Step 1 — Gather your data first

Before you even open the GST portal, make sure you have these ready:

• Sales summary — total taxable value, CGST, SGST, IGST, cess collected
• Purchase register — ITC from B2B purchases (match it against GSTR-2B)
• RCM liability — reverse charge on import services and unregistered vendor payments
• Previous period ITC balance — carry-forward from your electronic credit ledger

Step 2 — Log in to the GST portal

Head to gst.gov.in → Services → Returns → Returns Dashboard. Pick the financial year and period, then click "PREPARE ONLINE" next to GSTR-3B.

Step 3 — Table 3.1: Outward supplies

Report your total sales split across these buckets:

• 3.1(a) — Taxable outward supplies (the main one)
• 3.1(b) — Zero-rated supplies (exports + SEZ)
• 3.1(c) — Nil-rated and exempt supplies
• 3.1(d) — Inward supplies under reverse charge
• 3.1(e) — Non-GST outward supplies

Step 4 — Table 4: ITC claimed

This is where most mistakes happen. The portal auto-populates eligible ITC from GSTR-2B now, which helps — but you still need to verify.

• 4(A) — ITC available (auto-populated from GSTR-2B)
• 4(B) — ITC reversed (Rule 42/43, ineligible under Section 17(5))
• 4(C) — Net ITC = 4(A) − 4(B)
• 4(D) — Ineligible ITC (blocked credits)

Step 5 — Table 5: Exempt and non-GST supplies

Report nil-rated, exempt, and non-GST supplies — split by inter-state and intra-state. Straightforward if you've been tracking these separately.

Step 6 — Table 6: Pay the tax

The portal computes your liability from Table 3.1, offsets ITC from Table 4, and shows the remaining balance payable via electronic cash ledger. Generate a challan (PMT-06) and pay before filing.

Step 7 — Preview, pay, and file

Preview the return, double-check every number, generate the challan if cash payment is due, then submit. Sign with DSC or EVC (Aadhaar OTP).

One critical thing: GSTR-3B cannot be revised once filed. If you spot an error after submission, the only fix is to adjust in the next period's return.

What happens if you file late?

• Late fee: ₹50/day (₹25 CGST + ₹25 SGST) — capped at ₹10,000 per return
• Nil return: ₹20/day (₹10 CGST + ₹10 SGST)
• Interest: 18% per annum on outstanding tax, from due date to payment date
• 2+ months of non-filing? Your GSTIN can be suspended

These penalties add up fast. A two-week delay on ₹1 lakh tax costs roughly ₹700 in late fees plus ₹700 in interest.

Five mistakes that get businesses in trouble

1. GSTR-1 vs GSTR-3B mismatch — The department flags differences in outward supply values between these two returns. Reconcile before filing.
2. Claiming more ITC than GSTR-2B shows — The 5% cap is strictly enforced.
3. Wrong ITC offset order — IGST must be exhausted first. The portal usually handles this, but manual overrides can go wrong.
4. Missing reverse charge liability — Import of services and payments to unregistered vendors are frequently missed.
5. Filing nil when tax is actually due — Treated as suppression and can trigger penalty proceedings under Section 73/74.

How 1010 makes this effortless

Honestly, the manual process above is painful — and that's exactly why we built 1010. Here's what changes when you use it:

• All table values are auto-filled from your sales and purchase registers
• ITC is reconciled against GSTR-2B before you file — mismatches are flagged, not discovered later
• The optimal ITC offset order is computed to minimise your cash outflow
• You get a reminder 5 days before the deadline with a one-click review dashboard

No more last-minute scrambles on the 19th. Try it free — no credit card needed.