A GST interest calculator works out the interest on a late GST payment under Section 50 of the CGST Act. Enter the unpaid tax and either the due date and payment date or the days delayed, and this free tool applies the formula Interest = Tax × rate% × days ÷ 365. The rate is 18% per year for late payment of tax and 24% for excess input tax credit claimed. For example, ₹10,000 late by 30 days at 18% works out to about ₹147.95 interest.
Miss a GST due date and interest starts adding up under Section 50 of the CGST Act. This free GST interest calculator tells you exactly how much: enter the unpaid tax, the due date and the payment date, and it counts the days and applies the correct rate for you.
Late payment of tax is charged at 18% per year, while excess input tax credit or an undue reduction in output tax attracts 24%. The tool shows the days delayed, the interest, and the total you need to pay.
Key takeaways
- GST interest formula: Interest = Tax × rate% × days ÷ 365.
- Late payment of tax: 18% per year (Section 50(1)). Excess ITC or undue reduction of output tax: 24% per year.
- Days are counted from the day after the due date up to the actual payment date.
- Interest is charged on the net cash liability (tax paid in cash after using ITC), following the post-2020 amendment.
Why use this gst interest calculator?
Section 50 rates built in
Pick 18% for late tax or 24% for excess ITC, or set a custom rate.
Auto day-count
Enter the due and payment dates and it counts the days for you.
Clear total
Shows days delayed, interest and tax plus interest together.
Free and private
No signup, and nothing you enter is stored.
How to use it
- Enter the unpaid tax (the net cash liability you paid late).
- Choose the rate: 18% for late payment, 24% for excess ITC, or custom.
- Enter the due date and the actual payment date (or type the days directly).
- Read the days delayed, the interest, and the tax-plus-interest total.
Worked example: ₹10,000 tax, 30 days late
Suppose ₹10,000 of GST is paid 30 days after the due date, at 18% per year:
| Item | Calculation | Result |
|---|---|---|
| Interest | 10000 × 18% × 30 ÷ 365 | ₹147.95 |
| Total payable | 10000 + 147.95 | ₹10,147.95 |
Which GST interest rate applies?
| Situation | Rate (per year) | Section |
|---|---|---|
| Late payment of tax | 18% | 50(1) |
| Excess ITC claimed / undue reduction of output tax | 24% | 50(3) |
Since the 2020 amendment, interest on a late GSTR-3B is charged only on the net cash liability, that is the tax you actually paid in cash after adjusting available input tax credit, not on the gross tax.
Interest is not the same as the late fee
Two different charges can apply to a late GST return, so do not confuse them:
- Interest (this tool): 18% or 24% per year on the tax, for the days delayed.
- Late fee: a per-day charge for filing the return late, commonly ₹50 per day (₹20 per day for a nil return), split across CGST and SGST, subject to a cap.
This calculator covers the interest. Check the current late-fee amounts and caps on the GST portal, as they change from time to time.
Popular use cases
- Estimating interest before filing a late GSTR-3B.
- Businesses reconciling GST dues and working out the cash impact of a delay.
- Accountants giving clients a quick, correct interest figure.
- Checking the cost of paying a tax liability a few weeks late.
- Planning a payment date to keep interest to a minimum.
Frequently asked questions
What is the interest rate on late GST payment?
Late payment of GST is charged at 18% per year under Section 50(1). Claiming excess input tax credit or an undue reduction in output tax attracts 24% per year under Section 50(3).
How is GST interest calculated?
Interest = tax × rate% × days ÷ 365. For ₹10,000 that is 30 days late at 18%, the interest is 10000 × 0.18 × 30 ÷ 365 = about ₹147.95.
From which date are the days counted?
From the day after the due date up to the actual date of payment. Enter both dates in the tool and it counts the days for you.
Is GST interest charged on gross tax or net?
After the 2020 amendment, interest on late GSTR-3B is charged on the net cash liability, meaning the tax paid in cash after using available input tax credit, not the gross tax.
Is interest the same as the GST late fee?
No. Interest (18% or 24% per year) is on the unpaid tax. The late fee is a separate per-day charge for filing the return late, commonly ₹50 per day or ₹20 for a nil return.
Does interest apply if I have enough input tax credit?
If your liability is fully covered by ITC and there is no net cash payable, there is generally no interest under Section 50(1), since interest applies to the net cash liability.
Is this an official GST interest calculator?
It is a free estimate that applies the standard Section 50 formula. Always confirm the final figure on the GST portal or with your tax advisor before paying.
Is this GST interest calculator free?
Yes, completely free with no signup and no limits. Nothing you enter is stored.
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