Invoice Late-Fee Calculator
Calculate the late fee owed on an overdue invoice.
Assumptions used in this calculation
- Proration: Prorates the monthly rate by days late rather than charging a flat fee per partial month, some contracts may specify a flat per-month fee instead.
About this calculator
Late-payment terms are usually quoted as a monthly rate, like 1.5% per month, but an invoice rarely goes unpaid for a neat whole number of months, which leaves the question of exactly how much late fee to charge for, say, 45 days overdue rather than a clean one or two months. This calculator takes the invoice amount, the monthly late-fee rate, and the number of days the payment is overdue, and prorates the monthly rate linearly by days late (rate × days late ÷ 30) to compute the exact late fee owed. Instead of manually converting a monthly percentage into a daily rate and multiplying by the exact day count — a calculation that's simple in theory but fiddly to get precisely right — this calculator gives freelancers and small businesses a fast, defensible late-fee figure to add to a follow-up invoice or payment reminder for any client that pays past terms.
Worked example
₹50,000 invoice, 1.5%/month, 45 days late
Result: Late fee = ₹1,125
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