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
| Feature | GSTR-1 | GSTR-3B |
|---|---|---|
| Purpose | Declare outward supply details | Pay net GST liability |
| Data type | Invoice-level detailed data | Consolidated summary |
| Affects buyer? | Yes — populates buyer's GSTR-2B | No impact on buyers |
| Tax payment? | No — informational only | Yes — actual tax deposit |
| Due date (monthly) | 11th of next month | 20th of next month |
| Filing order | File first (11th) | File second (20th) |
| Amendments | Can amend in later period's GSTR-1 | Cannot 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.