Free tool · no sign-up
Overdue interest calculator
Work out the interest on a late invoice — days overdue, interest and the total due — and send the party a reminder.
Interest rate (% a year)
How it works
- 1Enter the bill and due dateThe amount, when it was due and when it was paid (or today).
- 2Set the interest rate18% a year, or the rate written on your invoice.
- 3Send the reminderInterest and total due, in a message ready for WhatsApp.
Runs in your browser. Nothing you type or upload is sent to Cashflow OS.
How the calculator works
Enter the invoice amount, the date it was due, when it was paid (leave it blank for today) and the yearly interest rate. You get the days overdue, the interest at simple interest and the total now due — and a ready reminder you can send on WhatsApp.
In Cashflow OS the same figures come straight from your TallyPrime books: every party's overdue bills, how many days late each one is, and a reminder in one tap. See the features.
Questions people ask
How is overdue interest worked out?
Simple interest: amount × rate × days overdue ÷ 365. Days are counted from the day after the due date to the payment date (or today).
What rate should I use?
The rate written on your invoice or agreed with the party. For dues to registered micro and small enterprises, the MSMED Act provides for compound interest at three times the RBI bank rate — check the current rate and your position with your CA.
Is the interest taxable or subject to GST?
Interest charged for late payment is generally treated as part of the value of supply for GST. Ask your CA how to invoice it in your case.
This calculator is general information, not legal or tax advice. Check the rate and how to charge it with your CA.
