GSTR-1 vs GSTR-3B: What's the Difference? | Kallapotti Learn

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 GSTR-1 reports sales details; GSTR-3B pays tax. Both are mandatory but serve different purposes. Learn the differences and what happens when they don't match.

  5 min read  Updated 15 March 2026  Ahopez Innovations Team GSTR-1GSTR-3BGST ReturnsTax Filing GSTR-1 and GSTR-3B are both mandatory GST returns but serve very different purposes. GSTR-1 is a detailed sales declaration; GSTR-3B is a summary return for tax payment. You must file both every month or quarter.

## Key Differences

FeatureGSTR-1GSTR-3BPurposeDeclare outward supply detailsPay net GST liabilityData typeInvoice-level detailed dataConsolidated summaryAffects buyer?Yes — populates buyer's GSTR-2BNo impact on buyersTax payment?No — informational onlyYes — actual tax depositDue date (monthly)11th of next month20th of next monthFiling orderFile first (11th)File second (20th)AmendmentsCan amend in later period's GSTR-1Cannot amend filed GSTR-3B## What Happens When GSTR-1 and GSTR-3B Don't Match?

Tax authorities use automated reconciliation to compare your GSTR-1 outward supply data with GSTR-3B. Significant mismatches can trigger:

-  Scrutiny notices under Section 61 of CGST Act
-  Demand for additional tax, interest, and penalty
-  Suspension or cancellation of GSTIN for persistent mismatches
-  Blocking of ITC for your buyers if sales declared in GSTR-3B are higher
 Important Always ensure the taxable turnover declared in GSTR-3B ≥ taxable turnover in GSTR-1 for the same period. Understating in GSTR-3B while correctly filing GSTR-1 is a common cause of demand notices.

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