GST Late Fee and Interest Calculator

Two separate charges apply when you file a GST return late:

• Late fee (Section 47): a fixed amount per day of delay, from the day after the due date until you file, up to a cap that depends on your turnover. It applies even to nil returns, and is paid in cash.
• Interest (Section 50): 18% a year on tax paid late, calculated on the part paid in cash (net of input tax credit), from the day after the due date until you pay.

Worked example

A trader with ₹1 crore turnover last year files the GSTR-3B due on 20 July on 10 August: 21 days late. Late fee = 21 × ₹50 = ₹1,050 (₹525 CGST + ₹525 SGST), within the ₹2,000 cap. If ₹1,00,000 of tax was paid in cash on 10 August, interest = ₹1,00,000 × 18% × 21 ÷ 365 = ₹1,035.62. Total ₹2,085.62.

Points people miss

• Proposed, not in force: on 8 October 2026 the 57th GST Council recommended waiving the late fee on a delayed GSTR-3B (Section 39(1) return) for taxpayers with turnover up to ₹5 crore in the previous year, if it is filed by the end of the month in which it was due. Until CBIC notifies this (not done as of 11 October 2026), the late fee above still applies and this calculator uses the current rules.
• The GSTR-1 late fee is charged in your next GSTR-3B, not in GSTR-1.
• For GSTR-9, the late fee runs until the complete annual return, including GSTR-9C where required, is filed (Circular 246/03/2025).
• A return can't be filed more than three years after its due date (enforced on the GST portal from the November 2025 tax period), so a long delay can mean you can't file at all.
• From the January 2026 period, the GST portal itself works out GSTR-3B interest and fills it in Table 5.1 of your next GSTR-3B, allowing for the lowest balance in your cash ledger between the due date and payment (Rule 88B(1)). You can't lower that figure, only raise it, so the portal's number may differ slightly from this estimate.
• Interest is charged on the cash portion of tax paid late. Wrongly availed and used input tax credit also attracts interest at 18%.

Learn how to avoid delays in our guides to filing GSTR-1, GSTR-1 vs GSTR-3B and the GSTR-3B lock and three-year time bar.

Sources: Notification 19/2021-CT (GSTR-3B), Notification 20/2021-CT (GSTR-1), Notification 21/2021-CT (GSTR-4), Notification 07/2023-CT (GSTR-9), Circular 246/03/2025, GSTN advisory on the three-year bar, GSTN advisory on GSTR-3B interest (Jan 2026).