How to use this GST interest calculator
- Enter the GST paid late. Use the amount paid in cash after the due date, not tax settled with input tax credit.
- Set the due date and the date you paid. For monthly GSTR-3B filers the due date is usually the 20th of the following month, but check the date that applied to you.
- Choose the reason. Late payment of tax is charged at 18% a year. Input tax credit that was wrongly claimed and used is charged at 24% a year.
- Read the result. You see the interest, the number of days, the daily cost and what you owe in total. The chart and table show how fast interest builds if payment slips further.
The formula
Interest = Tax paid late × Rate × Days late ÷ 365 Rate is 18% (0.18) for late payment under Section 50(1), or 24% (0.24) for excess ITC under Section 50(3). Days run from the day after the due date to the date of payment.
Worked example
A business owes ₹50,000 of GST in cash for September, due on 20 October 2026, and pays it on 15 November 2026. That is 26 days late. Interest is ₹50,000 × 0.18 × 26 ÷ 365 = ₹641.10, about ₹24.66 for every day of delay. The total payment comes to ₹50,641.10.
If the same ₹50,000 were input tax credit wrongly claimed and used, the 24% rate would make the interest ₹854.79 for the same 26 days.
Interest is charged on net cash liability
Interest on late payment is worked out on the tax you actually pay in cash from the electronic cash ledger after the due date. If part of your liability is covered by input tax credit already available in your credit ledger, that part does not attract interest. That is why the calculator asks for the GST paid late in cash rather than your total output tax.
Interest builds every day. At 18% a year, each ₹1 lakh paid late costs about ₹49 a day. Paying even a few days earlier saves real money, and paying on time avoids interest entirely.
Interest vs late fee
| Interest | Late fee | |
|---|---|---|
| Why it is charged | Tax paid after the due date | Return filed after the due date |
| How it is worked out | A percentage of the tax, per day | A fixed amount per day, with a cap |
| Rate | 18% a year (24% for excess ITC) | Set by notification, varies by return and turnover |
| Covered by this calculator | Yes | No: check the GST portal |
Because late fee caps have been revised several times, this calculator deliberately covers interest only. For the current late fee on a particular return, use the figures shown on the GST portal when you file.
Tips to avoid GST interest
- Pay as early as you can. Interest keeps running until the tax is paid, so even a few days matter. How cash already sitting in your ledger is treated depends on the current rules, so check the portal's interest figure.
- Keep a buffer. Set aside GST collected on sales in a separate account, so cash is ready on the due date.
- Reconcile input tax credit monthly. Claims that later turn out to be ineligible can attract 24% interest once used.
- Watch the calendar. Quarterly filers under the QRMP scheme have different payment dates from monthly filers.
Need to check the tax itself? Use the GST calculator to add or remove GST and split it into CGST, SGST or IGST. For general interest maths, the simple interest calculator uses the same per-day approach.
Frequently asked questions
What is the interest rate on late GST payment?
How is GST interest calculated?
Is interest charged on the whole tax liability?
Is the late fee the same as interest?
How do I pay GST interest?
Sources and further reading
Independent, official guidance on this topic. Rules differ by country, so check the regulator where you live.
- GST: Central Board of Indirect Taxes and Customs · CBIC, Government of India
- GST portal: returns, payments and rate notifications · Goods and Services Tax Network
This calculator gives estimates for education and planning. It is not financial advice, and your lender's figures may differ. See how we calculate.