How to File GSTR-1A to Amend Your GSTR-1 in India

To file GSTR-1A and amend your GSTR-1, open the GSTR-1A tile on the Returns dashboard of the GST portal after you have filed GSTR-1, add any records you missed or amend the records that were wrong for the same tax period, then file the statement with DSC or EVC before you file GSTR-3B. GSTR-1A is an optional amendment return, reintroduced from the August 2024 tax period, that exists for one job: to fix outward-supply errors while the same period's liability is still open. It cannot change the recipient GSTIN, it carries no government fee, and most businesses complete it in under one working day. This guide covers what GSTR-1A is, who can file it, the exact availability window for monthly and quarterly filers, the step-by-step portal process, what you can and cannot amend, the effect on a recipient's input tax credit, how it differs from amending in the next period's GSTR-1, and the mistakes that cost real money.

What Is GSTR-1A?

GSTR-1A is an optional return that lets a GST-registered supplier amend records already filed in GSTR-1, or add records missed in GSTR-1, for the same tax period, after filing GSTR-1 and before filing GSTR-3B. It corrects outward supplies inside the period that produced them, so the right tax liability flows into that period's GSTR-3B.

Before GSTR-1A returned, a filed GSTR-1 could not be revised. If a supplier spotted an understated invoice or a missed sale after filing, the only route was to amend it in the next month's GSTR-1. That created a stubborn gap: the original period's GSTR-1 stayed wrong, while GSTR-3B reflected a different figure, and the correction sat one period later. GSTR-1A removes that lag by letting the supplier rebuild the period's outward-supply picture before the liability is finalised in GSTR-3B.

The form mirrors GSTR-1 closely. It carries 15 tables, numbered 4 to 15A, that match the corresponding GSTR-1 tables. Tables 4 to 8 are used to add records that were left out of GSTR-1, while Table 9 amends earlier B2B invoices, debit notes, and credit notes, and Table 10 amends supplies to unregistered persons. The ARN and the taxpayer details auto-populate, and downward amendments are entered with a minus sign for the differential value. Because the layout is familiar, a supplier who can file GSTR-1 can file GSTR-1A without learning a new structure.

Why GSTR-1A Was Reintroduced

A version of GSTR-1A existed when GST began in 2017 but was suspended within months along with the original GSTR-2 and GSTR-3 matching design. It returned through Notification 12/2024-Central Tax dated 10 July 2024, which inserted a proviso to Rule 59(1) and added Rule 59(4A) to the CGST Rules, 2017. The portal made it available from the August 2024 tax period, first usable to amend the GSTR-1 filed for July 2024. The reintroduction answered a long-standing demand from taxpayers who wanted a clean way to correct outward supplies in-period rather than carrying errors forward.

Who This Guide Is For

This guide is written for business owners, accounts teams, and finance managers who file GST returns and report outward supplies, whether monthly or under the QRMP scheme. It covers the supplier side of the correction: how to amend or add outward-supply records in GSTR-1A and how that feeds your own GSTR-3B. Any business with an active GST registration that files GSTR-1 should know how this facility works, because a single understated invoice left uncorrected can cascade into interest, a mismatch notice, or a buyer's lost credit.

Why GSTR-1A Matters: Fixing Errors Before GSTR-3B Locks

The value of GSTR-1A is timing. GSTR-3B is where a supplier declares and pays the period's tax. Once that liability is set, correcting an outward-supply error becomes a multi-month exercise with interest and reconciliation attached. GSTR-1A lets you fix the error while the same period's liability is still open, so you pay the correct tax the first time.

Consider what happens without it. A supplier files GSTR-1 on the 11th, then notices a B2B invoice was entered as ₹50,000 instead of ₹5,00,000. If the only correction route is next month's GSTR-1, the supplier either under-declares tax in the current GSTR-3B to match the wrong GSTR-1, or declares the correct tax in GSTR-3B and lives with a GSTR-1 that is ₹4,50,000 short for the period. The first choice short-pays tax and invites interest under Section 50; the second creates a GSTR-1 versus GSTR-3B mismatch. GSTR-1A closes both doors by letting the supplier amend the invoice to ₹5,00,000 before GSTR-3B is filed, so GSTR-1 and GSTR-3B agree and the right tax is paid on time.

The Same-Period Correction Advantage

The net effect of GSTR-1 plus GSTR-1A auto-populates the supplier's own GSTR-3B for the same period. This is the central benefit: an amendment made on the 16th is reflected in the liability the supplier declares on the 20th. A missed ₹2,00,000 sale added through GSTR-1A on the 16th raises the auto-populated output tax in GSTR-3B by ₹36,000 at 18%, which the supplier pays with that month's return. There is no carry-forward, no interest on a delayed declaration, and no separate amendment entry months later. The period is closed clean, with outward supplies and tax liability stating the same numbers.

Fewer Mismatches and Scrutiny Triggers

A gap between the liability declared in GSTR-1 and the tax paid in GSTR-3B is one of the most common reasons the department raises a query. Where GSTR-1 liability exceeds GSTR-3B by a set threshold, the system can issue an intimation under Rule 88C of the CGST Rules in Form DRC-01B, requiring the supplier to explain or pay the difference. By aligning the two returns within the same period, GSTR-1A directly reduces the chance of such an intimation. It turns a potential notice into a non-event, because there is nothing left to reconcile once both returns carry the corrected figures.

Recovering Tax You Over-Reported

The benefit runs both ways. Errors that overstate supplies are as common as those that understate them, and they cost real working capital. If an invoice was keyed as ₹5,00,000 when the true value was ₹50,000, the supplier would otherwise over-declare ₹81,000 of IGST at 18% and pay tax that was never due. A downward amendment in GSTR-1A, entered as a differential with a minus sign, reduces the auto-populated liability in the same period's GSTR-3B, so the supplier pays only the correct ₹9,000. Without GSTR-1A, that ₹81,000 would sit blocked until the next period's amendment unwound it, tying up cash for a full cycle. Correcting in-period keeps the tax paid equal to the tax due, in both directions, which is the whole point of the facility.

Who Can File GSTR-1A and When

GSTR-1A is open to any regular taxpayer who files GSTR-1 and GSTR-3B. The only hard conditions are sequence based: GSTR-1 for the period must already be filed, and GSTR-3B for that period must not yet be filed. The facility serves both monthly filers and quarterly filers under the QRMP scheme, with the timing adjusted to each filing pattern.

Monthly Filers

A monthly filer reports outward supplies in GSTR-1 by the 11th of the following month and pays tax in GSTR-3B by the 20th. GSTR-1A sits in the window between these two dates. Once GSTR-1 is filed, the GSTR-1A tile becomes active and stays available until the moment GSTR-3B is filed. Most monthly filers who need a correction file GSTR-1A between the 12th and the 19th, after reconciling the filed GSTR-1 against their books and before locking liability in GSTR-3B.

Quarterly (QRMP) Filers

Under the Quarterly Return, Monthly Payment scheme, a supplier files GSTR-1 quarterly, with optional monthly uploads through the Invoice Furnishing Facility (IFF) for the first two months. For these taxpayers, a quarterly GSTR-1A opens after the quarterly GSTR-1 due date, the 13th of the month following the quarter, or its actual filing date, whichever is later, and stays open until the quarterly GSTR-3B is filed. Records reported in both the IFF and the quarterly GSTR-1 can be amended through this single quarterly GSTR-1A, and the combined effect auto-populates the quarterly GSTR-3B, due on the 22nd or 24th depending on the state.

The Exact GSTR-1A Availability Window

Getting the window right is the difference between a clean in-period fix and a missed opportunity that pushes the correction to a later return. The rule is the same for everyone: open after GSTR-1, close at GSTR-3B. The dates differ only by filing frequency.

Two phrases in this table carry the weight. "Whichever is later" means that if you file GSTR-1 early, on the 5th, the GSTR-1A window still opens only after the due date passes, not on the day you filed. "When GSTR-3B is filed" means the close is event driven, not date driven: filing GSTR-3B on the 17th closes the window on the 17th, three days before the statutory due date. The practical takeaway is to finish any GSTR-1A amendment before you sit down to file GSTR-3B, because the act of filing GSTR-3B itself shuts the door.

Where GSTR-1A Sits in the Monthly GST Cycle

GSTR-1A is one link in a fixed monthly chain, and seeing the full sequence makes the window obvious. The amendment can change a period's outcome only while it sits between the supplier's GSTR-1 and the supplier's GSTR-3B. The table below maps the cycle for a monthly filer, with the dates that anchor each step.

The sequence shows why the supplier's own correction is in-period while the buyer's credit shifts one period forward. Your GSTR-1A feeds your GSTR-3B for the same month, so your liability is right immediately. The same amendment reaches the buyer only after their current GSTR-2B has been drafted on the 14th, so it settles into their next month's statement through IMS. For a QRMP filer the same logic applies on a quarterly clock: the quarterly GSTR-1A sits between the quarterly GSTR-1 and the quarterly GSTR-3B, and amendments reach buyers in the following statement. Mapping your internal close to this chain, with reconciliation finished before GSTR-3B, keeps every correction inside the window where it still counts.

What You Can and Cannot Amend in GSTR-1A

GSTR-1A is wide in scope but has one firm boundary. You can correct almost every field on an outward-supply record, and you can add records you forgot, but you cannot change who the recipient is. The table below sets out the line.

What You Can Amend

Within a record, value, tax rate, place of supply, invoice number, and document details are all editable in GSTR-1A. You can also add a record that never reached the original GSTR-1, which is the practical answer to a missed sale. For supplies to unregistered persons, the portal applies one structural rule: if a place of supply with a given GST rate was already declared in GSTR-1, a new rate for that same combination cannot be added through Table 7 of GSTR-1A and must instead go through the amendment route in Table 10. This keeps the consolidated rate-wise reporting internally consistent.

What You Cannot Amend: The Recipient GSTIN

The one field GSTR-1A locks is the recipient GSTIN. If you reported a B2B invoice against the wrong customer, GSTR-1A will not let you reassign it to the correct GSTIN. The reason is that the invoice has already flowed to a buyer; reassigning it inside the same-period amendment would disturb credit that the system has already communicated. The fix is to amend the invoice in a following period's GSTR-1, where the structured amendment tables handle a GSTIN correction and the change is communicated cleanly to both the wrong and the right recipient.

The 15 Tables of GSTR-1A

GSTR-1A reproduces the GSTR-1 table structure so the amendment maps cleanly onto the original report. Knowing which table holds which correction saves time and prevents an entry from landing in the wrong place. The summary below lists the tables that matter most in day-to-day amendments.

A useful mental model is that the lower tables, 4 to 8, are for things you forgot, and the higher tables, 9 and 10, are for things you got wrong. A sale that never appeared in GSTR-1 is added as a fresh record in Table 4 to 8. An invoice that appeared with the wrong value or rate is amended in Table 9 or 10. Both routes feed the same period's GSTR-3B, but choosing the right table keeps your GSTR-1A summary readable and your reconciliation straightforward.

How GSTR-1A Affects the Recipient's ITC, GSTR-2B, and IMS

An amendment to your outward supply is, on the other side of the transaction, a change to your customer's input tax credit. GSTR-1A is therefore not only a supplier convenience; it reshapes what the buyer can claim. The timing of that effect is precise and worth understanding, because it differs for your own liability and your customer's credit.

For your own GSTR-3B, the effect is immediate and in-period: the net of GSTR-1 and GSTR-1A populates the same month's liability. For the recipient, the effect lands one period later. The input tax credit for any supply you declare or amend through GSTR-1A is reflected in the recipient's GSTR-2B for the next tax period, not the period being amended. So a correction you make in your June GSTR-1A appears in your customer's July GSTR-2B. This one-period shift exists because the recipient's GSTR-2B for the amended period has already been generated; the amended record updates the following statement instead.

Since the Invoice Management System (IMS) went live in October 2024, those amended and added records reach the recipient through their IMS dashboard before they settle into GSTR-2B. The buyer sees each amended invoice as an inbound record and chooses to accept, reject, or keep it pending, exactly as they would for a normal supplier filing. This means a GSTR-1A correction does not silently change a buyer's credit; the buyer still acts on it. Our guide on how to accept or reject invoices in the GST IMS explains the recipient side in full, and the supplier-side basics live in our GSTR-1 monthly return guide.

This split timing has a practical consequence for reconciliation. Because your liability moves in-period but the buyer's credit moves one period later, the two sides of an amended invoice are never recorded in the same month. A supplier who amends a ₹2,00,000 invoice in a June GSTR-1A reports the ₹36,000 of tax in June, while the buyer reconciles the matching credit in July. When a customer compares its purchase register to its GSTR-2B, an amendment from your side will appear in the month after you made it, not the month of the original invoice. Explaining this one-period lag upfront prevents a buyer from rejecting a legitimate amended record in IMS simply because it arrived later than expected, which is a frequent and avoidable cause of credit disputes.

GSTR-1A vs Amending in the Next Period's GSTR-1

GSTR-1A is not the only way to correct an outward supply. The older route, amending in a later period's GSTR-1 through its amendment tables (such as Table 9A for B2B invoices and Table 9C for credit and debit notes), still exists and is sometimes the only option. Knowing which to use, and when, prevents both missed windows and unnecessary mismatches.

The decision is mostly about timing and the recipient GSTIN. If you catch the error before filing GSTR-3B and it does not involve the customer's GSTIN, GSTR-1A is almost always the better tool, because it keeps the period clean and avoids interest. If you have already filed GSTR-3B, or you must reassign an invoice to a different recipient GSTIN, the next period's GSTR-1 amendment is the only route. Many businesses now use both in sequence: GSTR-1A for in-period fixes each month, and the next period's amendment tables for the rare correction discovered after GSTR-3B or the occasional GSTIN error. For complex or high-value corrections, structured GST amendment assistance can keep the two routes from colliding.

Step-by-Step: How to File GSTR-1A on the GST Portal

The full process runs across 8 steps, from confirming the error to verifying the corrected liability in GSTR-3B. Most suppliers complete it in well under one working day once their reconciliation is ready. Keep your filed GSTR-1, the underlying invoices, and a reconciliation against your books open before you start.

Step 1: Confirm the Error and That GSTR-1A Is the Right Tool

Pin down exactly what is wrong in the filed GSTR-1: an understated or overstated value, a wrong tax rate, an incorrect place of supply, a wrong document number, or a record left out altogether. Confirm two things before opening the portal. First, the correction relates to the same tax period as the GSTR-1 you filed. Second, it does not require changing the recipient GSTIN, which GSTR-1A cannot do. If a wrong customer GSTIN is the only issue, stop here and plan the fix for the next period's GSTR-1 instead. For every other field, GSTR-1A is the correct route, and a quick reconciliation against your books and e-invoices will surface each record that needs attention.

Step 2: Check the GSTR-1A Availability Window

Confirm the window is open. GSTR-1A becomes available after the GSTR-1 due date or its actual filing date, whichever is later, and remains open until you file GSTR-3B for the period. For a monthly filer, that is from after the 11th until you file GSTR-3B by the 20th. For a QRMP filer, it is from after the quarterly GSTR-1 due date until the quarterly GSTR-3B is filed. If GSTR-3B is already filed, the window has closed and you must use the next period's GSTR-1 amendment tables. Do not file GSTR-3B until your GSTR-1A is complete.

Step 3: Log In and Open the GSTR-1A Tile

Visit gst.gov.in and log in with your GSTIN credentials. Go to Services, then Returns, then Returns Dashboard. Select the financial year, quarter, and month of the period you are amending. The GSTR-1A tile appears alongside the GSTR-1 tile for that period. Click Prepare Online on the GSTR-1A tile to open the amendment statement. The GSTIN, legal name, trade name, and ARN auto-populate, so you move straight to the tables. If the tile is greyed out, recheck that GSTR-1 is filed and GSTR-3B is not.

Step 4: Add Missed Records or Amend Existing Records

Enter each correction in the correct table. To add a record missed in GSTR-1, use Tables 4 to 8 according to the supply type: Table 4 for B2B, Table 5 for large B2C inter-state, Table 6 for exports and SEZ, Table 7 for other B2C, and Table 8 for exempt and nil-rated. To amend a record already reported, use Table 9 for B2B invoices, debit notes, and credit notes, and Table 10 for supplies to unregistered persons. Enter the corrected figures in full; for a downward amendment, the differential is captured with a minus sign. Save each record as you go.

Step 5: Handle HSN, Advances, and Document Series

Correct the supporting tables if GSTR-1 was wrong in those areas. Amend the HSN-wise summary in Table 12, entering a minus sign for any downward differential. Correct advances received or adjusted in Table 11, and the document series and counts in Table 13. If you make supplies through e-commerce operators, review Tables 14, 14A, 15, and 15A for supplies covered by Section 52 and Section 9(5). These tables often need amendment only when the underlying invoice corrections in Tables 9 and 10 change the totals they summarise.

Step 6: Generate the Summary and Resolve Flagged Errors

Click Generate Summary. The portal validates every record and marks processed entries in green and errored entries in red. Common red flags include a value mismatch, an invalid combination of GST rate and place of supply, or a duplicate document number. Open each red record, correct the flagged issue, and regenerate the summary. Repeat until the summary completes with no errors. You can delete an individual record at this stage, or use the reset option to clear all records and start the entry again if needed.

Step 7: Preview the Consolidated Summary and File

Click Proceed to file to open the table-wise consolidated summary. This shows the net effect of every addition and amendment across the tables. Compare the net tax figure against your reconciliation to confirm it matches what you expected to correct. When it agrees, select the authorised signatory and file the statement using DSC for companies and LLPs, or DSC or EVC for other taxpayers. The portal generates an ARN confirming that GSTR-1A is filed for the period. Save the ARN and the filed statement for your records.

Step 8: File GSTR-3B and Verify the Auto-Populated Liability

Open GSTR-3B for the same period. The net impact of GSTR-1 plus GSTR-1A auto-populates your output tax liability, so the figures now reflect the corrected position. Verify each value against your books, pay any additional tax that the correction created, and file GSTR-3B. Filing GSTR-3B closes the GSTR-1A window for the period, so this is the last step. The amended and added records then reach your recipients through their IMS dashboard and appear in their next period's GSTR-2B. A walk-through of the liability side lives in our GSTR-3B filing guide.

A Worked Example: Correcting a May 2026 GSTR-1

A concrete example shows how GSTR-1A turns three errors into one clean filing. Assume a manufacturer files GSTR-1 for the May 2026 tax period on 11 June 2026 and, while reconciling on 14 June, finds three problems before filing GSTR-3B, which is due on 20 June 2026.

The Three Errors

First, a B2B invoice to Customer A was entered with a taxable value of ₹50,000 instead of the correct ₹5,00,000, understating IGST at 18% by ₹81,000 (₹90,000 correct against ₹9,000 reported). Second, a B2B sale to Customer B for ₹2,00,000, carrying ₹36,000 IGST at 18%, was omitted from GSTR-1 entirely. Third, an invoice to Customer C was reported against the wrong recipient GSTIN. The first two are value and omission errors that GSTR-1A can fix; the third is a recipient GSTIN error that it cannot.

The GSTR-1A Filing and Its Effect

On 16 June 2026 the manufacturer opens GSTR-1A for May 2026. It amends Customer A's invoice in Table 9 to ₹5,00,000, adding ₹81,000 of IGST, and adds Customer B's missed ₹2,00,000 invoice in Table 4, bringing in ₹36,000 of IGST. The net additional output tax is ₹1,17,000. After filing GSTR-1A with DSC, this ₹1,17,000 auto-populates the May 2026 GSTR-3B. The manufacturer pays the corrected liability and files GSTR-3B on 19 June, within the due date, so no interest under Section 50 arises. The wrong-GSTIN invoice for Customer C is left untouched in GSTR-1A and corrected instead in the June 2026 GSTR-1.

Two outcomes stand out. The supplier's May liability is now correct and paid on time, with GSTR-1 and GSTR-3B in agreement, so no Rule 88C intimation can arise for the period. For the buyers, Customer A's extra ₹81,000 of credit and Customer B's ₹36,000 reach their IMS dashboards and reflect in their June 2026 GSTR-2B, one period after the amendment. Customer C's correction, being a GSTIN change, follows the slower next-period GSTR-1 route. Repeated each cycle, this habit keeps reported supplies, tax paid, and buyer credit aligned with almost no carry-forward.

Cost of Filing GSTR-1A

GSTR-1A is a free facility on the GST portal. There is no government fee to add or amend records, and no separate due date that could attract a late fee. The meaningful costs are indirect and almost entirely within your control.

The real economics favour using GSTR-1A whenever an error appears. Correcting a ₹1,00,000 understatement in-period costs nothing but a few minutes, while the same error carried forward and discovered later can attract interest at 18% per annum under Section 50, a DRC-01B intimation, and the time cost of a reply. You can estimate the late-fee exposure on the related returns with our GST late fee calculator. The cheapest path is consistent in-period correction, because every rupee of tax stated and paid on time is a rupee that never becomes a notice.

Common Mistakes to Avoid

Beyond the technical steps, four habits quietly undermine the value of GSTR-1A. Avoiding them is the difference between a clean period and a carried-forward problem.

1. Filing GSTR-3B Before Reconciling GSTR-1

Filing GSTR-3B closes the GSTR-1A window. Reconcile your filed GSTR-1 against your books and post any GSTR-1A correction before you file GSTR-3B, every cycle. Treating GSTR-3B as the final action, not the first, preserves the in-period fix.

2. Trying to Change the Recipient GSTIN

GSTR-1A cannot reassign an invoice to a different customer GSTIN. Do not waste the window attempting it. Route every recipient GSTIN correction to a later period's GSTR-1 amendment tables, and use GSTR-1A only for value, rate, place of supply, and missed records.

3. Forgetting the Minus Sign on Downward Amendments

Downward corrections, including HSN summary reductions in Table 12, are entered as a differential with a minus sign. Entering a downward change as a positive figure overstates supplies. Check the sign on every reduction before generating the summary.

4. Expecting the Buyer to Get Credit in the Same Period

A GSTR-1A amendment reaches the recipient's GSTR-2B in the next tax period, not the amended one. If a customer is chasing credit for the corrected invoice, explain the one-period timing so they look for it in the following month's IMS and GSTR-2B.

Decision Checklist: Should You File GSTR-1A?

When you spot an outward-supply error, run through this checklist before acting. It points you to GSTR-1A or to the next period's GSTR-1, and stops a wrong move that wastes the window.

1. Have you already filed GSTR-1 for the period? If not, simply correct GSTR-1 directly before filing; GSTR-1A is not yet available.
2. Have you already filed GSTR-3B for the period? If yes, the GSTR-1A window is closed; correct in the next period's GSTR-1 amendment tables.
3. Does the fix involve changing the recipient GSTIN? If yes, GSTR-1A cannot do it; route the correction to a later GSTR-1.
4. Is it a value, rate, place of supply, or missed-record error? If yes, and the window is open, file GSTR-1A in the matching table.
5. Does the correction increase your tax? If yes, ensure the additional tax is paid through GSTR-3B by its due date to avoid interest under Section 50.
6. Is the summary fully green? Resolve every errored record, regenerate, then file GSTR-1A and finish with GSTR-3B.

Common Issues and How to Resolve Them

A handful of issues account for most GSTR-1A problems. Each has a clear fix once you understand the underlying rule.

The GSTR-1A Tile Is Not Available

The tile appears only after GSTR-1 is filed and before GSTR-3B is filed for the period. If it is missing, first confirm GSTR-1 for that exact financial year, quarter, and month is filed. Then confirm GSTR-3B for the period is not yet filed, because filing it closes the window. If both conditions are met and the tile is still missing, recheck the period selected on the Returns dashboard, since an early file before the due date may delay activation until the due date passes.

The Correction Did Not Flow Into GSTR-3B

If GSTR-3B does not reflect your amendment, the usual cause is an unfiled or incomplete GSTR-1A. Reopen the period and confirm GSTR-1A was filed and shows an ARN, not merely saved. Check that the summary was fully green when filed, since an errored record may not have been committed. Once GSTR-1A is correctly filed, the net of GSTR-1 and GSTR-1A auto-populates the same period's GSTR-3B liability.

A Buyer Says the Amended Credit Is Missing

Remind the buyer that a GSTR-1A amendment lands in their GSTR-2B for the next tax period, after passing through their IMS dashboard. Ask them to check the following month's IMS for the amended record and accept it. If a wider GSTR-1 versus GSTR-3B mismatch has already drawn a department query, our GST notice reply assistance can help structure a response with the supporting reconciliation.

An Error Surfaced After GSTR-3B Was Filed

Once GSTR-3B is filed, GSTR-1A is no longer available for the period. Correct the record in the next period's GSTR-1 using its amendment tables, such as Table 9A for B2B invoices. If the correction increases the original period's tax, pay the differential with interest under Section 50 from the original due date, since the in-period window has passed.

Related Resources

• How to File GSTR-1 Monthly Return: the original outward-supply return that GSTR-1A amends.
• How to File GSTR-3B Online: where the corrected liability auto-populates and locks the window.
• How to Accept or Reject Invoices in GST IMS: the recipient side, where amended records appear.
• GST Return Filing: assistance for monthly and quarterly GST returns end to end.
• GST Amendment: assistance for in-period and later-period corrections.
• GST Late Fee Calculator: estimate late fees on related returns.

Summary

Filing GSTR-1A is the way to amend or add records to a filed GSTR-1 for the same tax period before GSTR-3B locks the liability. Open the GSTR-1A tile after GSTR-1, amend value, rate, place of supply, or missed records in the matching tables, remember that the recipient GSTIN cannot be changed here, file with DSC or EVC, and finish with GSTR-3B. Used in-period, it keeps GSTR-1 and GSTR-3B in agreement, avoids interest under Section 50, and reduces Rule 88C mismatch intimations, while the corrected credit reaches your buyers through their IMS and next period's GSTR-2B. Done every cycle, GSTR-1A turns return corrections from a carried-forward burden into a clean, same-period routine.