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Indirect Tax Laws · Returns

Furnishing Details of Outward Supplies (GSTR-1, IFF) for CA Final

Updated 5 October 2026

GSTR-1 is the return in which a registered person reports outward supplies under Section 37. Under Section 37(1), monthly filers file by the 11th of the next month. QRMP filers file quarterly by the notified 13th after the quarter and may report B2B invoices of the first two months through IFF. Errors are corrected in a later GSTR-1.

Understand Furnishing Details of Outward Supplies (GSTR-1, IFF)

Every registered taxable person who makes supplies must tell the department what he sold. GSTR-1 is that statement. Section 37 of the CGST Act requires the details of outward supplies made in a tax period to be furnished, and Rules 59 and 60 prescribe the form, content and manner.

Why does it matter? The details you report flow to your buyer's auto-drafted statements (GSTR-2A and 2B). The buyer claims input tax credit on that basis. So your GSTR-1 is the source of your customer's credit. A wrong or late GSTR-1 hurts the buyer first.

Section 37(1) excludes an Input Service Distributor, a non-resident taxable person, a composition taxpayer (a person paying tax under Section 10), a person required to deduct tax (Section 51) or collect tax (Section 52), and an OIDAR supplier under Section 14 of the IGST Act. These persons file the returns prescribed under Section 39 instead (for example, GSTR-5A for OIDAR). A normal regular taxable person files GSTR-1.

The contents follow the nature of the sale. Supplies to registered persons are reported invoice-wise. Inter-State supplies to unregistered persons above the prescribed invoice-value limit are also reported invoice-wise. Other supplies to unregistered persons are reported in consolidated, State-wise form. Credit notes, debit notes, advances received, HSN summary and documents issued are also reported.

The QRMP scheme (Quarterly Return filing with Monthly Payment of tax) helps small taxpayers. A registered person with aggregate turnover up to ₹5 crore in the preceding financial year can opt in. He files GSTR-1 and GSTR-3B quarterly but pays tax every month. For the first two months of the quarter he may use the Invoice Furnishing Facility (IFF) to report B2B supplies, so that his buyers get credit without waiting for the quarter-end.

Errors are not corrected by editing the old return. You correct them in a later GSTR-1 (the period in which you notice the error), subject to the time limit in Section 37. You also pay any extra tax with interest.

Key rules to remember

Due date: monthly GSTR-1
11th of the month following the tax period
Section 37(1) fixes the 11th of the next month for monthly filers. The 13th for QRMP filers and for IFF is prescribed by notification under the QRMP framework. Use the date given in the question.
Due date: quarterly GSTR-1 (QRMP)
13th of the month following the quarter
Quarters end in June, September, December and March, so the dates fall in July, October, January and April.
IFF due date
13th of the month following the month (first two months of the quarter only)
IFF is not available for the third month of the quarter; those invoices go in the quarterly GSTR-1.
IFF limit
IFF may be used for a month only if the total taxable value of B2B supplies in that month is up to ₹50 lakh. IFF is optional.
Only B2B supplies to registered persons, plus credit and debit notes for such supplies, can go in IFF. B2C supplies are not allowed. If the month's B2B supplies exceed ₹50 lakh, IFF cannot be used for that month and all its invoices are reported in the quarterly GSTR-1. You cannot split the month between IFF and GSTR-1 on this basis.
QRMP eligibility
Aggregate turnover ≤ ₹5 crore in the preceding financial year, and the previous return due must have been furnished
The option is exercised PAN-wise, so it applies to all registrations under the same PAN. It continues for the financial year unless changed under the rules.
Monthly tax payment under QRMP
Pay by the 25th of the month following each of the first two months (Form GST PMT-06)
The tax for the third month is paid with the quarterly GSTR-3B. The monthly amount is paid either by the fixed sum method (35% of the cash tax liability paid in the preceding quarter's GSTR-3B) or by the self-assessment method (actual tax liability of the month, net of input tax credit).
Rectification time limit
Correct in the GSTR-1 of the period when the error is found, not later than the earlier of: 30th November following the end of the financial year, or the date of furnishing the annual return
This is the rectification rule in Section 37(3). It applies to errors or omissions in the details furnished; you pay the tax and interest, if any, on that account. Check the current text of Section 37 for any further bar on furnishing details after a time limit, and apply it only if the question or the Act as given states it.
Persons outside Section 37
ISD, non-resident taxable person, composition taxpayer (Section 10), person required to deduct tax (Section 51) or collect tax (Section 52), and OIDAR supplier (Section 14 of the IGST Act)
They file the returns prescribed under Section 39 instead of GSTR-1. OIDAR suppliers file GSTR-5A.

How to solve Furnishing Details of Outward Supplies (GSTR-1, IFF) questions

Use this order for any question on GSTR-1, IFF or amendment of outward supply details.

  1. 1Identify the person. Check whether he is a regular taxable person or one who files other returns (ISD, composition, TDS/TCS, non-resident, OIDAR).
  2. 2Check the filing frequency. Is he a monthly filer, or a QRMP filer whose turnover in the preceding year was within ₹5 crore?
  3. 3Fix the tax period and apply the due date: 11th for monthly, 13th after the quarter for QRMP, 13th for an IFF month.
  4. 4Classify each supply: B2B, B2C, export, credit or debit note. Decide whether it goes in the invoice-wise table, the consolidated table, or IFF (only B2B and notes, and only if the month's B2B taxable value is up to ₹50 lakh; IFF is optional).
  5. 5If there is an error or omission, find the period in which it was noticed. The correction goes in the GSTR-1 of that period, not the original period.
  6. 6Check the time limit for the correction under Section 37(3): the earlier of 30th November following the end of the financial year or the date of furnishing the annual return. Add the extra tax and interest, if any, in the GSTR-3B.
  7. 7State the conclusion in provision-facts-conclusion form, with the date or amount asked.

Quickest way: Three-check shortcut for dates and eligibility

When to use it: Use this when the question gives a date, a turnover and a type of supply, and asks 'by when' or 'can he use IFF'.

  1. Turnover check: up to ₹5 crore in the previous year means he can be a QRMP filer; otherwise monthly.
  2. Month check: for QRMP, month 1 or 2 means IFF is optional; month 3 means only the quarterly return.
  3. Supply check: IFF takes only B2B supplies and notes, and only if the month's B2B taxable value is up to ₹50 lakh. If it exceeds ₹50 lakh, no IFF for that month. Then remember 11 (monthly) or 13 (QRMP and IFF).

Common mistakes in Furnishing Details of Outward Supplies (GSTR-1, IFF)

  • Using the 20th as the GSTR-1 due date

    The 20th is the GSTR-3B date, and students mix the two returns.

    Fix: GSTR-1 is the 'sales return' with the 11th (monthly) or the notified 13th (QRMP). GSTR-3B is the summary return with a later date.

  • Saying QRMP filers pay tax quarterly

    The word 'quarterly' makes students assume everything is quarterly.

    Fix: Only the returns are quarterly. Tax for the first two months is paid monthly by the 25th through PMT-06.

  • Including B2C invoices in IFF

    Students treat IFF as a mini GSTR-1.

    Fix: IFF carries only B2B supplies to registered persons and related credit or debit notes, because its purpose is to give buyers credit early.

  • Allowing IFF for the third month of the quarter

    Students forget that the quarterly GSTR-1 already covers the third month.

    Fix: IFF is for months 1 and 2 only. Third-month invoices go straight into the quarterly GSTR-1.

  • Amending the original month's return

    Students think an error in June must be fixed in the June return.

    Fix: Amendments are made in the GSTR-1 of the month (or quarter) in which the error is noticed, within the Section 37 time limit.

  • Applying Section 37 to a composition dealer or ISD

    Students forget the exclusions listed in the section.

    Fix: Read the person first. Composition dealers, ISDs and the other excluded persons file different returns.

Worked examples

Example 1

Case: Ravi Traders, Pune, had aggregate turnover of ₹4.2 crore in the previous financial year and has opted for QRMP. For the quarter October to December, he made B2B supplies with a total taxable value of ₹30 lakh in October and ₹60 lakh in November (all B2B), and retail B2C sales in all three months. State the filing position for October and November and the due date of the quarterly GSTR-1.

Show the solution
  1. Provision: A person with turnover up to ₹5 crore in the preceding year can opt for QRMP. Ravi qualifies, since ₹4.2 crore is within ₹5 crore.
  2. IFF is optional for the first two months, covers only B2B supplies and notes, and can be used for a month only if the B2B taxable value of that month is up to ₹50 lakh.
  3. October: B2B taxable value of ₹30 lakh is within ₹50 lakh, so he may report these invoices through IFF by 13 November. His B2C sales cannot go in IFF.
  4. November: B2B taxable value of ₹60 lakh exceeds ₹50 lakh. IFF cannot be used for November at all, and he cannot report part of it in IFF and the rest in GSTR-1. All November invoices are reported in the quarterly GSTR-1.
  5. Quarterly GSTR-1 is due on 13 January. It must contain all November and December invoices, all B2C sales of the quarter, and the October invoices only if he did not use IFF for them. It must not duplicate invoices already reported in IFF.
  6. Tax for October and November is paid monthly by 25 November and 25 December through PMT-06; the tax for December is paid with the quarterly GSTR-3B.
  7. Method of monthly payment: Ravi pays either the fixed sum (35% of the cash tax liability paid in the preceding quarter's GSTR-3B) or the actual tax of the month under the self-assessment method. Either way, the payment is made through PMT-06.

Answer: Ravi is eligible for QRMP. October B2B invoices (₹30 lakh) can go in IFF by 13 November, as IFF is optional. IFF is not available for November because B2B supplies of ₹60 lakh exceed ₹50 lakh, so all November invoices, all B2C sales and the remaining invoices are reported in the quarterly GSTR-1 due on 13 January. Tax for October and November is paid by the 25th of the following month through PMT-06, under the fixed sum method or the self-assessment method.

Example 2

Case: Meera Enterprises, a monthly GSTR-1 filer, issued a June 2026 invoice to a registered buyer for ₹1,18,000 (taxable value ₹1,00,000 plus 18% GST). In its June GSTR-1 it wrongly reported the taxable value as ₹10,000. It notices the mistake while preparing the August return. How and where is it corrected?

Show the solution
  1. Provision: under Section 37, a person who finds an error or omission in the details furnished must rectify it and pay the tax and interest, if any, on that account.
  2. The correction is made in the GSTR-1 of the period in which the error is noticed, which here is August 2026. The June return is not reopened.
  3. Check the time limit: under Section 37(3), rectification is allowed up to the earlier of 30 November following the end of the financial year or the date of furnishing the annual return. For the financial year 2026-27, that date is 30 November 2027 (or the earlier date of filing the annual return). The error was noticed in August 2026, well before that date, so it is within the limit.
  4. Compute the shortfall. Correct taxable value is ₹1,00,000 and reported value was ₹10,000, so the difference is ₹90,000. At 18%, the extra tax is 18% × ₹90,000 = ₹16,200.
  5. Report the amended invoice in the amendment table of the August GSTR-1 with the correct value. Pay the extra tax of ₹16,200 in the GSTR-3B, along with interest for the period of delay, if the tax was short-paid.
  6. Impact on the buyer: the buyer's credit is based on the corrected invoice details reaching its auto-drafted statement, so the buyer should be informed.

Answer: The error is corrected through the amendment table of the August 2026 GSTR-1, not in June. The additional taxable value is ₹90,000 and the additional tax is ₹16,200, payable with applicable interest.

Exam tips

  • Write the section and rule in the first line (Section 37 of the CGST Act, read with Rules 59 and 60), then the facts and the conclusion.
  • Always state the date in the form 'the 13th of the following month' and mention the QRMP condition (turnover up to ₹5 crore).
  • In a case, check who is excluded from Section 37 before you discuss dates. This is a frequent hidden trap.
  • For MCQs, test the three traps: B2C in IFF, IFF in the third month, and quarterly tax payment under QRMP.
  • Amendment questions: name the period of correction, the time limit, and add tax with interest. These three points carry the marks.

Practice questions from Returns

Furnishing Details of Outward Supplies (GSTR-1, IFF): frequently asked questions

What is the due date of GSTR-1 for monthly and QRMP filers?

Under Section 37(1), monthly filers file GSTR-1 by the 11th of the following month. A QRMP filer files quarterly by the 13th of the month after the quarter, as prescribed by notification under the QRMP framework. Always read the date given in the question.

What is the Invoice Furnishing Facility (IFF)?

IFF lets a QRMP filer report B2B invoices and related credit and debit notes in the first two months of a quarter. It is optional. It can be used for a month only if the total taxable value of B2B supplies in that month is up to ₹50 lakh. It helps the buyer claim credit sooner.

How do I amend details already filed in GSTR-1?

Report the correction in the amendment table of the GSTR-1 for the period in which you notice the error. You must pay any extra tax with interest. Under Section 37(3), the correction must be made not later than the earlier of 30th November following the end of the financial year or the date of furnishing the annual return.

Who is not required to file GSTR-1 under Section 37?

Section 37(1) excludes an Input Service Distributor, a non-resident taxable person, composition taxpayers (Section 10), persons required to deduct tax (Section 51) or collect tax (Section 52), and OIDAR suppliers under Section 14 of the IGST Act. They file the returns prescribed under Section 39, such as GSTR-5A for OIDAR.