GST Interest & Late Fee Calculator
Work out what a delayed GST payment or a late return actually costs — interest on the tax paid in cash, plus the per-day late fee and the point at which that fee stops growing. Every rate is editable, because these figures are set by notification and change.
What a late GST payment actually costs
A delay has two separate costs, and they behave very differently. Interest compensates the exchequer for tax paid late — it accrues every day and never stops until you pay. A late fee is charged for filing the return itself after the due date — it accrues per day but is capped, so after a certain number of days it stops growing entirely. Confusing the two is the most common mistake in estimating what you owe.
The interest calculation is straightforward:
Interest = amount paid in cash × rate per annum × days delayed ÷ 365
At the rate currently notified under Section 50(1) — 18% per annum — a ₹50,000 cash liability paid 30 days late attracts ₹739.73 of interest. A useful sanity check: hold the same amount for a full 365 days and the interest is exactly ₹9,000, which is 18% of ₹50,000.
| Days delayed | Interest on ₹50,000 at 18% p.a. |
|---|---|
| 1 | ₹24.66 |
| 7 | ₹172.60 |
| 15 | ₹369.86 |
| 30 | ₹739.73 |
| 60 | ₹1,479.45 |
| 90 | ₹2,219.18 |
| 180 | ₹4,438.36 |
| 365 | ₹9,000.00 |
Interest runs on the cash portion, not your gross liability
This is the single most valuable thing to understand, and getting it wrong is expensive. Interest under Rule 88B(1) is calculated on the tax actually debited from your electronic cash ledger — that is, your liability after setting off input tax credit. It is not calculated on your gross output tax.
Whether interest ran on the gross or the net figure was litigated for years after GST began, which is why a good deal of older material online still shows the gross method. Enter your cash liability in the field above, not your total output tax.
The late fee, and the day it stops growing
The late fee is a flat per-day amount charged under each Act — currently notified at ₹25 under CGST plus ₹25 under SGST, so ₹50 a day in total for a return with tax payable, and ₹20 a day for a nil return. What almost no calculator shows is the cap, which depends on your annual aggregate turnover — and therefore the exact day the fee stops increasing:
| Annual aggregate turnover | Fee per day | Cap | Day the cap is reached |
|---|---|---|---|
| Up to ₹1.5 crore | ₹50 | ₹2,000 | Day 40 |
| ₹1.5 crore to ₹5 crore | ₹50 | ₹5,000 | Day 100 |
| Above ₹5 crore | ₹50 | ₹10,000 | Day 200 |
| Nil return (any turnover) | ₹20 | ₹500 | Day 25 |
So for a smaller taxpayer the late fee reaches ₹500 by day 10, ₹1,000 by day 20, ₹1,500 by day 30 and ₹2,000 by day 40 — and then stops. On day 60, day 180 or day 400 it is still ₹2,000. Past the cap, the only cost still growing is the interest.
That has a practical consequence worth acting on: once you are past the cap day, the marginal cost of a further day's delay is only the interest on your cash liability. Where you have several overdue periods and limited funds, clearing the one with the largest cash liability reduces the daily bleed fastest, because the late fees on the others have already stopped moving.
A worked example
A business with turnover under ₹1.5 crore owes ₹30,000 in cash and files 45 days late:
| Component | Working | Amount |
|---|---|---|
| Interest under Section 50 | ₹30,000 × 18% × 45 ÷ 365 | ₹665.75 |
| Late fee under Section 47 | ₹50 × 45 = ₹2,250, capped at ₹2,000 | ₹2,000 |
| Total | ₹2,665.75 |
Note that the late fee here is larger than the interest, and that it stopped growing five days before filing. On small liabilities the fixed fee usually dominates; on large ones the interest does.
Verify before you rely on this
Every figure on this page is set by notification, not fixed in the statute, and each can change without the underlying section changing at all. Treat the defaults as a starting point and confirm them against a current CBIC or GSTN source for your own filing:
- The 18% interest rate is the rate currently notified under Section 50(1). The section empowers the Government to notify a rate on the Council's recommendation, so it is not a constant. The rate field above is editable for exactly this reason.
- Wrongly availed input tax credit is a different head under Section 50(3), computed under Rule 88B(3) from the date the credit was utilised — not merely availed — and carrying its own notified rate, which may differ from 18%. Much of what circulates online still quotes a pre-2022 position for this head. If your case involves wrongly availed ITC, verify the applicable rate and enter it in the rate field rather than assuming the default.
- The ₹50 and ₹20 daily fees are notified reductions, not the statutory amounts. Section 47 itself prescribes a considerably higher per-day fee and cap; the lower figures apply because of notifications currently in force.
- The interest period runs from the day after the due date to the date of payment. This calculator uses a 365-day year.
To work out the underlying GST on an invoice in the first place, use the GST calculator. For tax deducted at source and its own interest and fee regime, see the TDS calculator, and for direct tax on business or salary income the income tax calculator.