GST Interest and Late Fee Calculator

A GST return that is filed late, or tax that is paid late, costs money in two separate ways. The first is interest on the tax that was not paid on time. The second is a late fee for each day the return is overdue. They are calculated differently, they may apply together, and a business that misses a date by a few weeks can find that the penalty is more than it expected. This page separates the two and shows each.

How interest is counted

Interest under section 50 of the GST Act is simple, not compound. The formula is tax paid late × rate × days ÷ 365, where the days run from the day after the due date to the day you pay. The page asks for the two dates in the YYYY-MM-DD form and counts the difference. The default rate is 18 percent a year. The field note explains that a higher rate of 24 percent applies to input credit that was wrongly claimed or reversed, so change the rate for that case.

How the late fee is counted

The late fee is a fixed amount for every day the return is overdue. The default is 50 a day, made of 25 for central GST and 25 for state GST. For a nil return the default is 20 a day, 10 of each. Both numbers are editable because they have been revised by notification several times. A cap box lets you stop the fee at the maximum for your turnover and type of return; if you leave it blank, the fee has no ceiling.

A worked example

The default is 2,50,000 of tax with a due date of 20 April 2026 and payment on 17 May 2026. That is 27 days late. Interest is 2,50,000 × 18% × 27 ÷ 365 = 3,328.77, the late fee is 27 × 50 = 1,350, and the total on top of the tax is 4,678.77. Interest accrues at 123.29 a day, so each extra day of delay adds that amount plus another 50 of fee. In the nil-return sample, filed 12 days late with no tax to pay, there is no interest and the fee is 12 × 20 = 240.

What is the base?

Interest applies to the tax payable in cash after input tax credit has been set off, as the page notes. If part of your liability was paid on time and part was not, enter only the part that was late. If the same return carries several late payments with different dates, run the page once for each.

Edge cases

If you pay on or before the due date the days are zero, and both amounts are zero. A payment date before the due date is treated as zero days. A date that is not in the YYYY-MM-DD form shows an error that gives an example. A rate of 0 removes interest, and a per-day fee of 0 removes the fee. A cap lower than the accrued fee limits the fee, and the page labels the line to say that it was capped.

Limits

The page does not know which return you are filing, so it cannot supply the cap or the per-day fee. It does not apply waivers or amnesty schemes that the government has announced from time to time. Interest on delayed refunds, on wrongly availed credit in the period it was used and on reversed credit follow their own rules. Confirm amounts with your tax adviser or the GST portal’s own calculation before paying.

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