Free GST Late Fee + Interest Calculator
Compute GSTR-1 / 3B late fee and Section 50 interest on unpaid tax for any return period.
How to calculate GST late fee and interest
Choose the return type
GSTR-1 (outward supplies) carries late fee only. GSTR-3B (summary + payment) carries late fee + Section 50 interest on unpaid tax.
Mark if it is a Nil return
A Nil return is one with zero outward supplies and zero tax liability. Daily fee is ₹20 (₹10 + ₹10) capped at ₹500.
Pick your turnover bracket
Annual turnover from previous FY decides the cap: ≤ ₹1.5 Cr → ₹2,000. ₹1.5–5 Cr → ₹5,000. > ₹5 Cr → ₹10,000.
Enter days late and unpaid tax
Days late = difference between actual filing date and the original due date. For GSTR-3B, also enter the tax amount you should have paid — interest is computed on it at 18% p.a.
Interest = unpaid tax × 18% × days / 365What this late-fee calculator does
The GST portal calculates late fees and interest automatically when you log in to file a delayed return — but it only shows you the final amount, not the breakdown. This calculator reverses that: enter your situation and see exactly how the late fee builds up, where the cap kicks in, and how much of the total is interest versus penalty.
Useful for two scenarios: (1) you are about to file a delayed return and want to budget the cash outflow, (2) you discovered a missed return and want to know whether to file immediately or wait for the next amnesty scheme.
How the daily late fee works
Two daily rates, set by the 2022 CBIC notification series:
- Regular return (any taxable supplies / tax liability): ₹50 per day, split as ₹25 CGST + ₹25 SGST. IGST is not levied as late fee.
- Nil return (zero supplies / zero tax): ₹20 per day, split as ₹10 + ₹10.
The clock starts ticking the day after the original due date and stops on the date the return is actually filed. Weekends and holidays count as full days — the GST portal does not give grace.
Worked example
You file GSTR-3B for May 2026 on 5 July 2026. Due date was 20 June 2026. Days late = 15. Regular (non-Nil) return. Daily fee × days = 50 × 15 = ₹750. That is the late fee before applying the cap.
The turnover-based caps
Late fees are capped per return to prevent them from spiraling out of control on long-delayed returns. The cap depends on your previous FY's aggregate turnover:
| Turnover (prev FY) | Cap per regular return | Cap per Nil return |
|---|---|---|
| Up to ₹1.5 Crore | ₹2,000 | ₹500 |
| ₹1.5 Crore to ₹5 Crore | ₹5,000 | ₹500 |
| Above ₹5 Crore | ₹10,000 | ₹500 |
If your daily-fee total exceeds the cap, the cap applies. For a small business (turnover ≤ ₹1.5 Cr), the regular cap is reached after 40 days late (50 × 40 = ₹2,000). Any further delay does not add to the late fee, but interest under Section 50 keeps accruing.
Section 50 interest — how it actually works
Late fee compensates the system for delayed filing; Section 50 interest compensates the exchequer for delayed payment. They are independent — you can have late fee with no interest (Nil return) or interest with no late fee (return filed on time but tax paid via challan late).
The rate is 18% per annum for late payment of self-assessed tax. The math:
Interest = unpaid tax × 18% × days / 365
Simple interest, computed daily, from the original GSTR-3B due date until the date the cash payment is made. Compounding does not apply for normal late payment of self-assessed tax.
A separate 24% per annum rate applies for excess ITC claimed and reduced output tax liability — that scenario is outside this calculator's scope; use it cautiously and consult your CA.
Worked example
GSTR-3B for May 2026 should have been filed with ₹2,00,000 tax paid by 20 June. You file on 5 July (15 days late). Interest = 2,00,000 × 18% × 15 / 365 = ₹1,479.45. Total cash outflow (return-specific): late fee ₹750 + interest ₹1,479.45 = ₹2,229.45.
When late fees do NOT apply
A few specific scenarios where the late fee is zero despite a delay:
- Return not yet activated for your registration. If you registered mid-month, the GST portal does not generate a return for the partial month. Your first return covers from the registration date.
- Composition scheme dealer filing CMP-08 / GSTR-4. Different fee structure applies (₹50/day capped at ₹2,000 for late CMP-08; ₹100/day capped at ₹500 for late GSTR-4 Nil; otherwise capped at ₹2,000).
- Genuinely Nil GSTR-3B during an amnesty period. When CBIC announces a Nil-return amnesty, late fees for past Nil returns are waived if filed within the amnesty window.
- System-down dates explicitly notified by CBIC. If the GST portal is down and CBIC issues a notification extending the due date, late fee for the affected days is waived. Always check the GST portal news feed during compliance week.
How to minimize late-fee exposure
- Pre-fund the cash ledger. Deposit estimated tax 2-3 days before the due date so a banking failure on the due date doesn't cause interest. The cash ledger balance is just a deposit — it stays with you until you use it.
- File GSTR-1 by the 11th even if data is incomplete. A return with a few minor errors filed on time saves the late fee; you can issue amendment notes (via Table 9 of next month's GSTR-1) later.
- Filing late but not yet 40 days late? The daily fee dominates. File ASAP — every day costs ₹50.
- Filing more than 40 days late? The late fee is capped, so further delay only adds 18%/yr interest on unpaid tax. Use this calculator to compare the cost of immediate filing vs waiting for an amnesty.
- Set up a CA review the day before the due date. Most "I forgot to file" cases are caught by an external eye.
From overdue tracker to compliant filings
ReadyBooks shows every GST return's status (filed, pending, overdue) on a single dashboard, sends reminders on the 8th, 18th, and on the due date, and computes the exact late fee + interest if you do miss a deadline. Free forever. Save to ReadyBooks above to start.