Late GST payments attract interest, usually at 18% per year on the outstanding tax. This free GST interest calculator works it out for you — enter the tax amount, number of days delayed and the rate, and it shows the interest and the total amount payable.
Handy before you file, so there are no surprises.
Why use this gst interest calculator?
Accurate day-count
Interest is calculated on the exact days delayed.
Default 18% rate
Pre-filled with the standard GST late rate; editable.
Total payable
Shows tax + interest so you know the full amount.
Free & instant
No signup — recalculate as often as you like.
How to use it
- Enter the unpaid GST (tax) amount.
- Enter the number of days the payment is delayed.
- Keep the default 18% p.a. rate or set your own.
- Read the interest and the total amount payable.
Popular use cases
- Estimating interest before filing a late return.
- Businesses reconciling GST dues and penalties.
- Accountants giving clients a quick figure.
- Checking the cost of a delayed payment.
Frequently asked questions
What is the interest rate on late GST?
It is generally 18% per annum on the outstanding tax for late payment. Certain cases (like excess ITC) can attract 24%. Confirm your case with an accountant.
How is GST interest calculated?
Interest = tax × (rate/100) × (days/365). This tool applies that formula for you.
From which date are days counted?
Usually from the day after the due date up to the actual payment date. Enter that number of days here.
Is this official?
It is a free estimate. Always verify the final figure on the GST portal or with your tax advisor.
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