Late fee and interest calculator

How it works

A late fee is charged for each day a return is filed after its due date, until it reaches the most it can be for that return. It comes in two equal halves: CGST and SGST. There is no late fee under IGST (the GST portal’s GSTR-3B manual).

Turnover here is your aggregate turnover in the previous financial year: the total value of all your sales, for every GSTIN under your PAN, not counting the GST. The lower maximums, for nil returns and for turnover up to ₹5 crore, apply to tax periods from Jun 2021.

In a Union territory without its own legislature, the second half is UTGST instead of SGST. We haven’t yet confirmed that its late fee is the same as the SGST one, so check the figure the GST portal shows.

How the days are counted

Days late = the filing date minus the due date. Filing on the due date isn’t late, and filing the next day is 1 day late. This is the formula in the GST portal’s own GSTR-3B manual.

Interest

Interest is charged on GST paid after its due date, at 18% a year (Notification No. 13/2017-Central Tax), from the day after the due date until the day the tax is paid. For a late GSTR-3B, the GST portal counts those days to the filing date, so the calculator does too, unless you enter another payment date.

Interest = tax paid late × 18 ÷ 100 × days late ÷ 365. The result is then rounded to the nearest rupee, as section 170 of the CGST Act says for every amount you pay: 50 paise or more rounds up, and less is dropped. The calculator rounds once, on the total. The GST portal may round in a different way, so its figure may differ by ₹1 or ₹2.

For the tax on a period’s own sales, declared in that period’s own return, only the part paid in cash counts: the part paid from your electronic cash ledger, not the part paid with input tax credit (ITC). The cash ledger holds the money you pay through the GST portal, by UPI, net banking, card or bank transfer, or at a bank’s counter (section 49(1) of the CGST Act and rule 87(3) of the CGST Rules). Cash that was already in the ledger on the due date, and stayed there until it paid the tax, doesn’t count either. This rule was added to rule 88B(1) by Notification No. 12/2024-Central Tax, dated 10 Jul 2024. It doesn’t apply to a return filed before then. In other cases, such as tax for an earlier period added to a later return, interest is on the full tax that stayed unpaid. The cash-only rule also stops applying once proceedings under section 73, 74 or 74A of the CGST Act have started for the period.

The calculator counts a year as 365 days, as the GST portal’s own formula does (a GSTN advisory says so). It isn’t yet confirmed whether a delay that runs over 29 Feb should count a year of 366 days. Either way, the GST portal’s figure is the one that counts.

A worked example

This is an example: the turnover, the tax and the filing date are made up. A monthly GSTR-3B for Sep 2026 was due on 20 Oct 2026.

1. It is filed on 30 Oct 2026. Days late: 30 Oct 2026 minus 20 Oct 2026 = 10 days.
2. Late fee: 10 days × ₹25 = ₹250 CGST, and ₹250 SGST: ₹500 in all.
3. The turnover is up to ₹1.5 crore, so the most the late fee can be is ₹1,000 each. The full ₹500 applies.
4. ₹50,000 of the tax was paid late, in cash, on the filing date. Interest: ₹50,000 × 18 ÷ 100 × 10 ÷ 365 = ₹246.58, rounded to ₹247.
5. To pay on top of the tax: ₹500 + ₹247 = ₹747.

Filed later, the late fee would grow by ₹50 a day until it reached the maximum, at 40 days late. The interest keeps growing until the tax is paid.

What it doesn’t cover

• Late fees for other returns, such as GSTR-4, GSTR-7 and GSTR-9.
• Interest on input tax credit wrongly taken and used.
• Late returns for tax periods before Jun 2021, and late returns filed before 1 Dec 2021. Waivers and amnesties changed many late fees then, so the calculator gives no figure for them: check the GST portal or ask a qualified tax professional. A return filed by its due date has no late fee, and the calculator says so. For a month before Jun 2021, it can’t work out interest on tax paid late either.