GST Return Filing Guide: GSTR-1, GSTR-3B and Due Dates

Which GST returns does a regular taxpayer file?

A normal taxpayer’s monthly cycle involves two returns to file, one optional correction form and two portal tools you act on but never file. New to the basics of tax types and credit? Start with what GST is and how it works.

GST return due dates as of September 2026

The standard due dates below come from the CGST Rules. The government can extend them for particular periods, so confirm on gst.gov.in before any deadline.

The legal basis is section 37 read with Notification 83/2020-Central Tax for GSTR-1, Rule 59(2) for IFF, Rule 61 for GSTR-3B and Rule 80 for the annual return. GSTR-9C applies only when aggregate turnover exceeds ₹5 crore, and taxpayers with turnover up to ₹2 crore are exempt from GSTR-9.

Monthly or quarterly: the QRMP scheme

Businesses with aggregate turnover up to ₹5 crore can opt for the Quarterly Return Monthly Payment (QRMP) scheme. They file GSTR-1 and GSTR-3B once a quarter, but still pay tax every month through a challan for the first two months of the quarter.

QRMP halves the number of returns, but it has a cost for businesses that sell to other registered businesses. Their buyers claim credit only after the invoice is reported. That is why many QRMP filers upload B2B invoices through IFF in months 1 and 2 instead of waiting for the quarterly GSTR-1.

GSTR-1: reporting your sales

GSTR-1 is the statement of outward supplies, and in 2026 it is the most important return to get right because GSTR-3B now flows from it. Each B2B invoice you report appears on your buyer’s IMS dashboard and decides their input tax credit.

The main tables are:

• B2B invoices (Table 4): sales to registered buyers, invoice by invoice with the buyer’s GSTIN.
• B2C large (Table 5): inter-state sales to unregistered buyers where the invoice value exceeds ₹1 lakh.
• B2C others (Table 7): all other consumer sales, reported as a rate-wise, state-wise summary.
• Credit and debit notes (Table 9B), exports, nil-rated and exempt supplies and advances.
• HSN summary (Table 12) and documents issued (Table 13).

Filing happens under Returns Dashboard: pick the period, prepare the tables online or upload through the offline tool, generate the summary, preview and file with DSC or EVC. If you spot an error after filing, GSTR-1A lets you amend that period’s details until you file GSTR-3B.

IMS: how buyers accept or reject invoices

The Invoice Management System, available on the GST portal since October 2024, lets a buyer accept, reject or keep pending every invoice a supplier reports. Only accepted invoices, plus those on which no action is taken, flow into the buyer’s GSTR-2B as eligible credit (GSTN advisory on IMS).

• Accept: the invoice goes into GSTR-2B.
• Reject: the invoice is left out of GSTR-2B.
• Pending: the invoice is carried forward to a later month, within the time limit in section 16(4).
• No action: treated as deemed accepted when GSTR-2B is generated.

A draft GSTR-2B is generated on the 14th of the following month. You can still act on invoices after that until you file GSTR-3B, but you must then recompute GSTR-2B. Once GSTR-3B is filed, no further IMS action is possible for that month.

Difference between GSTR 2A and 2B (GSTR-2A vs GSTR-2B)

The GSTR 2A and 2B difference comes down to one thing: GSTR-2A keeps changing, while GSTR-2B is a statement fixed for the period. Both list your purchases as your suppliers reported them, but only GSTR-2B is the statement you reconcile your input tax credit against before filing GSTR-3B.

The GST portal describes GSTR-2A as a read-only view, and the GSTN advisory on IMS sets out how GSTR-2B is generated (checked 6 October 2026). In practice, if a supplier files late, the invoice appears in your GSTR-2A as soon as it is filed, but it reaches GSTR-2B only for a later period.

GSTR-3B: the summary return and its locked tables

GSTR-3B is where tax is actually paid. The portal pre-fills it: outward liability from GSTR-1, GSTR-1A and IFF, and input tax credit from GSTR-2B.

The Table 3.1 lock was announced in a GSTN advisory of 7 June 2025 and the Table 3.2 lock in an advisory of 5 December 2025. From the January 2026 tax period, the portal also computes interest in Table 5.1 using the minimum cash-ledger balance under Rule 88B. It also auto-fills the tax liability breakup for supplies of earlier periods (GSTN advisory on interest).

The practical effect is simple: you can no longer fix a wrong sales figure inside GSTR-3B. Every correction has to go through GSTR-1A before you file, or through a later GSTR-1.

Step-by-step monthly filing workflow

This is the sequence a monthly filer follows, and the one employers expect an accounts executive to run without supervision.

1. Close the month’s sales and purchase entries in your accounting software and reconcile GST ledgers.
2. File GSTR-1 by the 11th, checking buyer GSTINs, invoice numbers and HSN codes.
3. Review the auto-drafted liability. If anything is wrong, file GSTR-1A for the same period.
4. Work through IMS: accept valid supplier invoices, reject wrong ones and keep doubtful ones pending.
5. Recompute GSTR-2B if you acted after the 14th, then reconcile it with your purchase register (our Excel formulas guide for accountants shows the XLOOKUP match).
6. Check the pre-filled GSTR-3B, including reversals in Table 4 and interest in Table 5.1.
7. Pay any cash liability and file GSTR-3B by the 20th with DSC or EVC.

Late fees, interest and the three-year bar

Missing a due date costs money and, eventually, the right to file at all. Late fee for GSTR-3B is ₹50 a day (₹20 for a nil return), CGST and SGST combined, subject to turnover-based caps. The cap is ₹500 for a nil return, ₹2,000 for turnover up to ₹1.5 crore and ₹5,000 for turnover up to ₹5 crore, under Notification 19/2021-Central Tax. Above ₹5 crore, the section 47 maximum of ₹10,000 applies. The notification sets the CGST half; SGST is equal.

Interest is payable on tax paid late, on the cash portion of the liability, and the portal now computes the minimum amount itself. Separately, section 39(11) of the CGST Act bars filing a return after three years from its due date, and similar limits apply to GSTR-1 and the annual return. Old pending returns cannot simply be filed late any more.

Common mistakes that cause GST notices

Most GST notices for small businesses trace back to a handful of avoidable errors:

• Wrong buyer GSTIN in GSTR-1, so the buyer’s credit lands with someone else.
• Reporting a B2B sale as B2C, which denies the buyer credit.
• Claiming credit that is not in GSTR-2B, or not reversing credit on unpaid supplier bills.
• Ignoring IMS and letting wrong supplier invoices be deemed accepted.
• Correcting liability in books but not through GSTR-1A before GSTR-3B.

Learning to file GST returns

Return filing is a hands-on skill: you learn it by preparing real tables and fixing real mismatches. Before you file for anyone, the business must hold a valid registration (see our GST registration process guide). If you plan to file for several clients, you can enrol under Rule 83; read how to become a GST Practitioner and what the GST practitioner career path looks like.

IPA – Institute of Professional Accountants teaches GSTR-1, IMS, GSTR-3B and reconciliation on practice data in its 2-month GST course in Delhi (placement assistance). Batches run at its Laxmi Nagar centre, near the metro station.

How we teach this at IPA

The GST course at IPA teaches returns in the order they are done: outward supplies go into GSTR-1, eligible credit is reconciled against GSTR-2B, and only then is GSTR-3B filed and the tax paid. Students work through this on the GST portal, and the online batches follow the same sequence of returns, challans and notices.

Frequently asked questions