GSTR-1 and GSTR-3B

Most registered businesses file two documents every month or quarter, and many treat them as two versions of the same thing. They are not. GSTR-1 is a statement of what the business sold, invoice by invoice, which feeds its customers’ credit. GSTR-3B is the return on which the business declares its tax, takes its credit and pays. They are made under different sections of the Act, for different purposes, and much of the system’s enforcement now works by comparing them.

This guide covers section 37 of the CGST Act, under which GSTR-1 is filed, and section 39, under which GSTR-3B is filed.

GSTR-1: a statement, not a return

Section 37(1) requires every registered person to furnish “the details of outward supplies … effected during a tax period”. It excludes Input Service Distributors, non-resident taxable persons, composition taxpayers, and persons deducting or collecting tax at source. The Explanation defines those details to include “invoices, debit notes, credit notes and revised invoices”.

The section describes GSTR-1 as a statement, and its main function is to pass information on. The details “shall … be communicated to the recipient of the said supplies”. This is the link with the credit conditions in section 16. A supplier’s GSTR-1 is what puts an invoice into its customer’s GSTR-2B, and an invoice not reported there cannot meet section 16(2)(aa).

Rule 59(4) of the CGST Rules sets the level of detail. Supplies to registered persons are reported invoice by invoice. Inter-State supplies to unregistered persons are reported invoice by invoice above one lakh rupees, and consolidated by State and rate below it. Intra-State supplies to unregistered persons are consolidated by rate.

Timing. Section 37(1) fixes the tenth day of the following month, but allows the Commissioner to extend it by notification. Notification No. 83/2020-Central Tax did so from 1 January 2021. GSTR-1 is now due by “the eleventh day of the month succeeding such tax period”. For quarterly filers, it is due by the thirteenth day of the month after the quarter.

GSTR-1A. A proviso to rule 59(1), added in 2024, lets a supplier amend or add to its GSTR-1 for a period in FORM GSTR-1A. Under rule 59(4A), it opens at the later of the GSTR-1 due date and the date the GSTR-1 is actually filed, and closes when the GSTR-3B for the same period is filed.

GSTR-3B: the return

Section 39(1) requires every registered person, with the same exclusions, to furnish for every calendar month “a return … of inward and outward supplies of goods or services or both, input tax credit availed, tax payable, tax paid and such other particulars”. That return is GSTR-3B. Rule 61(1) makes it due by the twentieth day of the following month.

Section 39(7) ties payment to the return. The registered person “shall pay to the Government the tax due as per such return not later than the last date on which he is required to furnish such return”. The return is where liability is set off against credit and cash, under the order the next guide covers. A GSTR-3B filed without payment is not a valid return. Section 2(117) defines a valid return as one “on which self-assessed tax has been paid in full”.

The portal now fills much of GSTR-3B itself. The tax liability is auto-populated from GSTR-1, GSTR-1A and the IFF. GSTN’s advisories record that it cannot be edited in GSTR-3B from the July 2025 tax period, and table 3.2 (inter-State supplies to unregistered persons and others) from the November 2025 tax period. An error is corrected at source, in GSTR-1A, not in GSTR-3B. The lock rests on the portal’s design and those advisories rather than on a rule: on 8 October 2026 the GST Council recommended new sub-rules (1A) and (1B) in rule 61 to provide for it, from the return for April 2027.

Section 39(8) requires a return for every tax period “whether or not any supplies … have been made”. A nil return is still a return, and missing it has consequences.

Quarterly filing, monthly payment

A proviso to section 39(1) allows the Government to notify persons who file quarterly. This is the Quarterly Return Monthly Payment scheme. Notification No. 84/2020-Central Tax opens it to registered persons with “an aggregate turnover of up to five crore rupees in the preceding financial year” who opt for it under rule 61A. A person whose turnover crosses five crore rupees during a quarter loses eligibility “from the first month of the succeeding quarter”.

Under rule 61(1)(ii), the quarterly GSTR-3B is due on the twenty-second or the twenty-fourth day after the quarter. The date depends on the State of the principal place of business. The twenty-second applies broadly to the western and southern States, and the twenty-fourth to the northern and eastern States and Delhi. The rule lists each one.

Payment remains monthly. For each of the first two months of the quarter, rule 61(3) requires the tax due to be deposited in FORM GST PMT-06 by the twenty-fifth of the following month. Section 39(7) allows either the actual tax due or an amount determined in a prescribed manner.

For sales to registered customers in the first two months, a quarterly filer may use the Invoice Furnishing Facility (IFF) under rule 59(2). This reports invoices up to fifty lakh rupees a month, between the first and thirteenth of the following month, so that customers need not wait for the quarter’s GSTR-1 to see them.

Filing in order, and a three-year limit

Both returns are now sequential. Section 37(4) bars a GSTR-1 for a period if one for any earlier period has not been filed. Section 39(10) bars a GSTR-3B for a period if any earlier GSTR-3B, or the GSTR-1 for the same period, is outstanding. Rule 59(6) adds that a GSTR-1 cannot be filed if the previous period’s GSTR-3B is outstanding. The practical effect is that an unfiled return cannot be skipped and returned to later. Everything after it waits.

Rule 59(6) also blocks GSTR-1 in three further cases: where the person has not furnished bank account details under rule 10A, and where an intimation under rule 88C, or one under rule 88D, both described below, has been neither paid nor answered.

From 1 October 2023, sections 37(5) and 39(11) bar filing after “the expiry of a period of three years from the due date”. The Government may relax this by notification on the Council’s recommendation. The portal began enforcing the bar from the November 2025 tax period, under GSTN’s advisory of 29 October 2025. It also offers an application to the jurisdictional officer to unbar returns for thirty days, though no notification under those provisos was found in CBIC’s list. Late Returns: Late Fee, Interest, the Three-Year Bar and Notices sets out the detail.

Correcting a return

A filed GSTR-1 or GSTR-3B is not amended directly. Errors are corrected in a later return.

For GSTR-1, section 37(3) requires an error or omission to be rectified. Any short payment of tax that results is paid with interest.

For GSTR-3B, section 39(9) allows rectification in the return for the month or quarter in which the error is noticed, subject to interest. Rectification is not available where the error comes to light “as a result of scrutiny, audit, inspection or enforcement activity by the tax authorities”. At that point the matter is the department’s, under the provisions covered in the guide on notices.

Both sections set the same outer limit. No rectification is allowed after the thirtieth day of November following the end of the financial year, or the date of the annual return, if earlier.

The two returns are compared

Since 2022 and 2023, the system tests the returns against each other and against suppliers’ filings. Three provisions do the work.

GSTR-1 against GSTR-3B. Rule 88C applies where the tax payable on GSTR-1 for a period exceeds that on GSTR-3B by more than a limit recommended by the Council. The person receives an intimation in FORM GST DRC-01B. Within seven days, it must pay the difference with interest or explain it. An unpaid and unexplained amount “shall be recoverable in accordance with the provisions of section 79”, the recovery provision, without a further show cause notice.

GSTR-3B against GSTR-2B. Rule 88D applies the same method to credit. Where credit taken in GSTR-3B exceeds what GSTR-2B shows as available, beyond the limit, the intimation is in FORM GST DRC-01C. Here an unpaid and unexplained amount is liable to be demanded under section 73, 74 or 74A.

Suspension. As the registration guide explained, rule 21A(2A) allows suspension where comparing GSTR-3B with GSTR-1 or GSTR-2B shows “significant differences or anomalies”.

The result is that the two returns must reconcile. A business can no longer report sales fully in GSTR-1 and pay on a lower figure in GSTR-3B, or claim credit in GSTR-3B that its suppliers have not reported.

A monthly cycle

For a monthly filer, the sequence each month is:

1. Issue invoices, debit and credit notes, and record them.
2. File GSTR-1 for the month, reporting supplies to registered persons invoice by invoice.
3. Act on suppliers’ invoices in the Invoice Management System, accepting, rejecting or keeping them pending. That decides what GSTR-2B shows.
4. Review GSTR-2B for the month, which shows the credit available from suppliers’ filings.
5. Amend GSTR-1 through GSTR-1A if needed, before GSTR-3B.
6. Prepare GSTR-3B. The output tax comes from GSTR-1 and GSTR-1A. Declare credit consistent with GSTR-2B and the conditions in section 16 and the restrictions in section 17.
7. Pay the net tax and file GSTR-3B by the twentieth.
8. Answer any intimation under rule 88C or 88D within seven days.

The portal steps for each of these, form by form, are in a separate set of procedure guides beginning with The GST Returns Calendar: Who Files What, and When.

The next guide covers the three electronic ledgers under section 49, through which the tax declared in GSTR-3B is actually paid.