R1 and 3B refers to GSTR-1 and GSTR-3B, the two main GST returns every regular taxpayer files.

GST R1 and 3B: Differences, Filing Order & 2026 Rules

TLDR

GST R1 and 3B refers to GSTR-1 and GSTR-3B, the two main GST returns every regular taxpayer files. GSTR-1 reports your sales invoice data to the GST portal. GSTR-3B is the summary return where you declare tax liability, claim input tax credit, and pay GST. Since July 2025, outward supply liability in GSTR-3B is non-editable, making GSTR-1 accuracy (and GSTR-1A corrections) more important than ever.

“R1” is shorthand for GSTR-1. “3B” means GSTR-3B. Together, GSTR-1 and GSTR-3B form the backbone of regular GST compliance in India. Yet many business owners only learn the difference after receiving a mismatch notice or finding that their buyer’s ITC is blocked.

This guide explains what each return does, how they connect, why they must match, and what to do when they don’t. It reflects the post-2025 reality where GSTR-3B liability is locked to GSTR-1 data and manual edits are no longer an option.

If you run a business or handle GST filing, get expert GST support before a small error becomes a notice.

What is GST R1 (GSTR-1)?

GSTR-1 is the monthly or quarterly statement of outward supplies filed by normal and casual registered taxpayers. It contains invoice-level details of all your sales and other outward supplies, including B2B invoices, B2C summaries, exports, credit notes, debit notes, advances, and HSN/SAC summaries. The GST portal defines it as a statement furnished electronically that covers goods and services supplied during the tax period.

Think of GSTR-1 as your sales register uploaded to the government. It does not involve any tax payment. Its job is to tell the system exactly what you sold, to whom, at what value, and under which tax rate.

Who files GSTR-1?

Every registered taxable person making outward supplies files GSTR-1, except input service distributors, composition taxpayers, persons liable to deduct TDS under Section 51, and persons liable to collect TCS under Section 52.

GSTR-1 due dates

Monthly filers must submit GSTR-1 by the 11th of the following month. Quarterly filers (under the QRMP scheme, available for turnover up to ₹5 crore) file by the 13th of the month after the quarter ends.

Nil GSTR-1

Even if you had zero business activity in a tax period, GSTR-1 must still be filed. You file it as a nil return, but you cannot skip it.

What is GSTR-3B?

GSTR-3B is the simplified summary return where taxpayers declare their total GST liability, claim eligible input tax credit (ITC), and pay the net tax for the period. The GST portal describes it as the form used to declare and discharge summary GST liabilities.

Where GSTR-1 is about reporting sales data, GSTR-3B is about settling the bill. It summarizes your output tax, your eligible ITC, and the difference you owe (or carry forward). No invoice-level detail appears here.

Who files GSTR-3B?

All normal taxpayers and casual taxpayers file GSTR-3B for every tax period, without exception.

GSTR-3B due dates

Monthly filers submit by the 20th of the following month. Quarterly filers submit by the 22nd or 24th of the month after the quarter, depending on the state/UT grouping notified by the government.

Nil GSTR-3B

Filing is mandatory even with no business. However, the portal allows a nil GSTR-3B only when strict conditions are met: no auto-populated data from GSTR-1/IFF, no data from GSTR-2B, no manual entries, and no outstanding interest or late fee.

A nil return is not the same as “no cash tax payable.” If you have sales, purchases, RCM liability, ITC, interest, or late fee, the return cannot be nil even if your net cash payment works out to zero. Practitioners on Reddit report that this distinction trips up many first-time filers, with one taxpayer describing how they accidentally filed nil under the wrong GSTIN and then struggled to correct a ₹23,980 liability.

GSTR-1 vs GSTR-3B: Difference Table

This comparison table covers the core differences between GST R1 and 3B.

Which is Filed First: GSTR-1 or GSTR-3B?

GSTR-1 always comes before GSTR-3B for the same tax period. The portal enforces this: GSTR-3B cannot be filed if GSTR-1 for the same period has not been filed. And under Rule 59(6)(b), the current period’s GSTR-1 cannot be filed if the previous period’s GSTR-3B remains pending.

The practical filing order for any month looks like this:

1. Finalize your sales register and books.

2. Prepare and file GSTR-1.

3. Review the auto-populated liability in GSTR-3B.

4. If GSTR-1 has errors and GSTR-3B is not yet filed, correct using GSTR-1A.

5. File GSTR-3B and pay/offset tax.

6. Save return PDFs, ARN, payment challan, and reconciliation worksheet.

This is not just a sequence. It is a control mechanism. Since GSTR-1 data now feeds directly into GSTR-3B liability (and that liability is locked), getting R1 right before 3B is the single most important step in monthly GST compliance.

For businesses managing GST across multiple GSTINs or states, CA-led return filing prevents the kind of sequence errors that trigger notices.

How GSTR-1 Data Flows into GSTR-3B

GSTR-3B is not prepared in isolation. The portal auto-populates it from two sources:

• GSTR-1 / GSTR-1A feeds your outward supply liability tables in GSTR-3B.

• GSTR-2B (the auto-generated ITC statement based on your suppliers’ GSTR-1 filings) feeds ITC and reverse charge values.

The flow works like this:

Books / invoices / e-invoices
        ↓
      GSTR-1
        ↓
GSTR-1A correction (if needed, before 3B)
        ↓
Auto-populated outward liability in GSTR-3B
        ↓
ITC from GSTR-2B + tax payment in GSTR-3B

E-invoice warning

If your business uses e-invoicing, invoice details from the Invoice Registration Portal (IRP) auto-populate into GSTR-1. Do not file GSTR-1 blindly just because data appears. Reconcile IRP data with your books, credit notes, exports, and e-commerce reports first. Editing auto-populated e-invoice details in GSTR-1 is allowed, but after edits, the source and IRN fields go blank.

What is GSTR-1A and Why It Matters Before Filing 3B

This section covers the correction mechanism that most generic “GSTR-1 vs 3B” articles underexplain, and it is arguably the most important change in recent GST compliance.

GSTR-1A is an amendment return that lets you correct records already filed in GSTR-1 or add records you missed, all within the same tax period. It becomes available after GSTR-1 is filed (or after its due date, whichever is later) and must be filed before GSTR-3B for the same period. Changes made through GSTR-1A auto-populate into GSTR-3B.

The non-editable liability change (July 2025 onwards)

From the July 2025 tax period, GSTN made auto-populated outward liability in GSTR-3B non-editable. This means you can no longer manually adjust sales liability numbers inside GSTR-3B. If your GSTR-1 has wrong values, the only correction route before 3B is GSTR-1A.

This is a fundamental shift. Before this change, many taxpayers and accountants treated GSTR-3B as the place to “fix” outward supply numbers. That option no longer exists.

Buyer-side timing impact

Here is a detail that affects vendor-buyer relationships: supplies declared or amended through GSTR-1A are available to the recipient in the next tax period’s GSTR-2B, not the current one. So if you correct an April invoice through April’s GSTR-1A, your buyer may only see it in May’s GSTR-2B.

Before you follow old advice

Many older forum answers (on CAclubindia threads from 2022 or 2023, for example) say “rectify in next return.” That approach may still apply after GSTR-3B is filed. But if GSTR-3B for the same period has not been filed yet, GSTR-1A is the cleaner, safer route. A 2026 CAclubindia expert thread confirmed exactly this: the taxpayer had filed March 2026 GSTR-1 with a wrong invoice, hadn’t yet filed GSTR-3B, and was directed to use GSTR-1A immediately.

Why GSTR-1 and GSTR-3B Must Match

GSTR-1 and GSTR-3B do not need to look identical table for table. But taxable value, tax liability by head (IGST, CGST, SGST), and timing must reconcile. If GSTR-1 shows outward supplies but GSTR-3B does not discharge corresponding tax, the system treats it as underpayment risk.

Matching GSTR-1 and GSTR-3B is not cosmetic bookkeeping. It is how the portal verifies whether the sales you reported have also been taxed and paid.

What goes wrong when they don’t match

1. DRC-01B under Rule 88C. When GSTR-1/IFF tax payable exceeds GSTR-3B tax paid beyond the prescribed threshold, the taxpayer receives an intimation in Part A of Form GST DRC-01B. You must either pay the differential tax with interest via DRC-03 or furnish reasons in Part B within seven days.

2. Interest on delayed payment. From January 2026, the portal’s interest computation in GSTR-3B Table 5.1 was enhanced. Auto-populated interest is non-editable downward.

3. Buyer ITC problems. If your B2B invoices are wrong or missing in GSTR-1, your buyer’s GSTR-2B will not reflect the ITC.

4. Annual return headaches. Mismatches carry forward into GSTR-9/9C reconciliation.

5. Filing blockage. Ignoring a Rule 88C intimation can restrict future GSTR-1/IFF filing.

6. Refund delays. Exporters and zero-rated suppliers face refund complications when R1 and 3B data is inconsistent.

Common Reasons for GSTR-1 and 3B Mismatch

Timing mismatches

An invoice reported in GSTR-1 in one month but tax paid through GSTR-3B in another. Credit notes issued later. Missed invoices added in a subsequent return.

Classification errors

B2B reported as B2C or the reverse. Export or SEZ supplies placed in the wrong GSTR-3B table. RCM supplies incorrectly categorized. E-commerce operator supplies under Section 9(5) mishandled.

Tax head errors

IGST used instead of CGST plus SGST, or vice versa. Place of supply errors. Interstate B2C not captured correctly in GSTR-3B Table 3.2.

Value and amount mismatches

Taxable value entered differently across returns. Rounding or decimal errors. Credit notes not adjusted. Debit notes placed in the wrong section.

System and data-source mismatches

E-invoice data auto-populated but not reconciled. E-commerce TCS data not matched with sales. IMS/GSTR-2B issues affecting ITC. Wrong GSTIN profile selected.

Practitioners on Reddit describe real-world versions of these problems regularly. One chartered accountants forum thread described a Meesho seller whose returns were filed with empty sales tables across multiple months while platform-side TCS data created confusion. E-commerce sellers should not file only from their accounting sales register. Reconcile marketplace order reports, return/refund data, TCS credits, and advertisement invoices before touching GSTR-1 and 3B.

Nil vs zero confusion

Filing nil when there were actually sales, purchases, RCM, or ITC. The portal’s strict nil-return conditions catch many first-time filers off guard.

What to Do If GSTR-1 and GSTR-3B Do Not Match

Here is a decision framework based on the most common scenarios.

Case 1: GSTR-1 filed, GSTR-3B not yet filed

Use GSTR-1A to correct or add outward supply records for the same period. Corrected values auto-populate into GSTR-3B. This is always the first option to explore.

Case 2: GSTR-1 shows higher tax than GSTR-3B

This triggers DRC-01B risk under Rule 88C. Reconcile whether tax was paid in another period, whether GSTR-1 has duplicate invoices, whether a credit note or amendment is missing, or whether GSTR-3B genuinely underpaid. If tax is short-paid, pay the differential with interest through DRC-03. If not, prepare a documented explanation with supporting reconciliation.

Case 3: GSTR-3B shows higher tax than GSTR-1

Check whether invoices were missed in GSTR-1, whether sales landed in wrong tables, or whether 3B included prior-period tax. Correct through GSTR-1A if before 3B filing. Otherwise, use eligible later-period amendment routes and keep a reconciliation file.

Case 4: Nil GSTR-1 filed by mistake

If GSTR-3B is not yet filed, use GSTR-1A to add the missed outward supplies. If GSTR-3B is already filed, move to amendment in a later period, but check time limits and interest exposure.

Case 5: Buyer says ITC is not visible

Confirm that the supplier filed GSTR-1 with the correct B2B classification and GSTIN. If GSTR-1A was used, the buyer may only see the corrected data in the next period’s GSTR-2B.

Case 6: Old return not filed

Check the three-year filing restriction. A June 2025 GSTN advisory confirms that returns including GSTR-1, GSTR-1A, and GSTR-3B are barred from filing after three years from their due date, with the portal restriction implemented from the July 2025 tax period.

Dealing with a mismatch notice or DRC-01B? Talk to a CA before responding, especially if the difference involves multiple periods or tax heads.

Mismatch triage summary

Reconciliation Checklist Before Filing

Before filing GSTR-1

• Match sales register with invoices.

• Reconcile e-invoice/IRP data with books.

• Verify B2B GSTINs.

• Check B2C large vs small classification.

• Review exports, SEZ, and deemed exports.

• Verify credit and debit notes.

• Check advances and advance adjustments.

• Confirm HSN/SAC summary.

• Reconcile e-commerce supplies and TCS data.

• Generate GSTR-1 summary and compare totals with books.

Before filing GSTR-3B

• Compare GSTR-1/GSTR-1A outward liability with GSTR-3B Table 3.1/3.2.

• Compare purchase register with GSTR-2B.

• Check RCM liability.

• Review ITC reversals and reclaims.

• Verify interest and late fee.

• Confirm tax-head utilization (IGST, CGST, SGST/UTGST, cess).

• Download draft GSTR-3B and review before payment.

If the portal auto-populates interest, do not simply override or ignore it. Recompute manually, compare with the portal value, and save your calculation file. One Reddit thread from early 2026 described a taxpayer encountering a GSTR-3B filing block because the IMS dashboard appeared stuck on an old period. These portal-level issues are real and more common than official documentation suggests.

After filing

• Save ARN for both returns.

• Download filed GSTR-1 and GSTR-3B PDFs.

• Save challan and payment details.

• Archive the reconciliation file.

• For corrections, keep working papers explaining the reason and supporting documents.

The Four-Way GST Reconciliation

Do not limit reconciliation to just GSTR-1 vs 3B. A stronger approach checks four layers:

1. Books vs GSTR-1. Are all sales invoices and credit notes reported correctly?

2. GSTR-1/GSTR-1A vs GSTR-3B. Is outward liability discharged correctly?

3. Purchase register vs GSTR-2B/IMS. Is ITC supported by supplier reporting?

4. GSTR-3B vs cash/credit ledgers. Was tax actually paid or offset correctly?

This framework catches problems that a simple two-return comparison misses.

Practical Examples

Example 1: Missed invoice, GSTR-3B not yet filed

An April invoice of ₹1,00,000 plus 18% GST was missed in GSTR-1. Since April’s GSTR-3B has not been filed, the taxpayer uses GSTR-1A to add the missed invoice. The corrected ₹18,000 liability flows into GSTR-3B automatically.

Example 2: GSTR-1 shows more tax than GSTR-3B

GSTR-1 reports output GST of ₹1,80,000. GSTR-3B only paid ₹1,20,000. The ₹60,000 gap crosses the prescribed threshold, triggering a DRC-01B intimation. The taxpayer must identify whether the difference was paid in another period, whether GSTR-1 has duplicates, or whether tax was genuinely underpaid. If underpaid, the fix is paying through DRC-03 with applicable interest.

Example 3: B2B invoice classified as B2C

A B2B invoice was mistakenly reported as B2C in GSTR-1. The buyer cannot see it for ITC purposes. If GSTR-3B is not yet filed, the classification is corrected through GSTR-1A. The buyer should expect the corrected data in the next period’s GSTR-2B.

Example 4: E-commerce seller with TCS mismatch

A marketplace seller relied solely on their accounting software for GSTR-1 but did not reconcile platform order reports, returns, commissions, and TCS. Multiple months of GSTR-1 showed empty or incomplete sales tables while the platform’s TCS data told a different story. The fix requires reconstructing sales from marketplace reports, filing amendments for past periods within statutory limits, and potentially paying interest on any short-paid tax.

Example 5: Wrong GSTIN selection

A business with multiple GSTINs filed under the wrong registration. Before filing, always confirm: GSTIN, trade name, state, tax period, return frequency, and filing status. Multi-GSTIN groups should require maker-checker approval before final submission.

Quick Glossary of Related Terms

Frequently Asked Questions

What is GST R1 and 3B?

GST R1 means GSTR-1, the statement of outward supplies filed by regular taxpayers. 3B means GSTR-3B, the summary return used to declare GST liability, claim ITC, and pay tax. Together, they form the core monthly (or quarterly) GST filing cycle.

Is GSTR-1 the same as GSTR-3B?

No. GSTR-1 reports invoice-level sales data. GSTR-3B summarizes tax liability and ITC at a consolidated level. They serve different purposes, but the numbers must reconcile.

Which is filed first, GSTR-1 or GSTR-3B?

GSTR-1 is always filed first. The portal will not allow GSTR-3B filing until GSTR-1 for the same tax period is submitted.

Can I edit GSTR-3B liability after July 2025?

No. Auto-populated outward supply liability in GSTR-3B became non-editable from the July 2025 tax period. Corrections must go through GSTR-1A before filing GSTR-3B.

What happens if GSTR-1 shows more tax than GSTR-3B?

The difference can trigger a DRC-01B intimation under Rule 88C. You must either pay the shortfall with interest through DRC-03 or explain the difference within seven days.

Can old GSTR-1 or GSTR-3B be filed anytime?

No. A GSTN advisory from June 2025 confirms that specified GST returns are barred after three years from their due date. The portal restriction is now active.

Why does my buyer not see ITC even after I corrected GSTR-1 through GSTR-1A?

Supplies declared or amended through GSTR-1A become available to the recipient in the next tax period’s GSTR-2B, not the current one.

Is GSTR-3B required if there are no sales?

Yes. GSTR-3B is mandatory for every tax period. A nil return is only permitted when strict conditions are met, including zero auto-populated data, zero manual entries, and no outstanding interest or late fee.

India’s GST system collected ₹22.27 lakh crore in gross revenue in FY 2025-26, up 8.3% year on year. With that kind of scale, the compliance machinery around GSTR-1 and GSTR-3B reconciliation is only getting tighter. The non-editable liability lock, Rule 88C intimations, three-year filing bars, and IMS workflows all point in one direction: get it right before you file, not after.

For GST return filing, GSTR-1 and 3B reconciliation, mismatch notices, or any compliance concern, reach out to Lalit Tyagi & Company for CA-led support across Delhi NCR, India, and for NRIs abroad.

This article is for informational purposes and does not constitute legal or tax advice. Consult a qualified professional for your specific situation.