Late Payment Fee Calculator

An invoice late payment fee calculator is a financial tool that calculates the penalty charges that accrue when an invoice is paid after its due date. It takes the original invoice amount, the number of days overdue, the fee type (fixed fee, percentage per month, or percentage per day), the fee rate, any grace period, and the compounding method (simple or compound). The calculator produces the total late fee, the new total amount due, the effective annual rate of the late fee, and a day-by-day accrual table showing how the fee builds over time. Our late payment fee calculator runs entirely in your browser with no data uploaded to any server.

1. Enter Your Invoice Details: Input the original invoice amount, the number of days the payment is overdue (or the due date), and any grace period. Select a jurisdiction preset (UK 8% + BoE base rate, EU statutory interest, US 1.5%/month) to auto-fill standard rates, or enter a custom fee structure manually.
2. Configure Late Fee Terms: Choose your fee type - fixed fee (a flat charge like $25 per late invoice), percentage per month (e.g. 1.5% of the invoice amount per month overdue), or percentage per day (e.g. 0.05% per day). Select whether the fee compounds (simple or compound interest) and set the compounding frequency.
3. Review the Complete Analysis: The calculator displays the total late fee, new total amount due, the effective annual rate of the late fee, and a detailed day-by-day fee accrual table. The accrual table shows how the late fee grows each day, with running totals of the fee amount and cumulative total due at each interval.

• Total Late Fee: The total penalty amount calculated based on your fee type, rate, days overdue, grace period, and compounding method. This is the additional amount owed beyond the original invoice amount.
• New Total Due: The original invoice amount plus the total late fee. This is the full amount the debtor must pay to settle the overdue invoice including all accumulated penalties.
• Effective Annual Rate (EAR): The annualized percentage rate of the late fee, which allows comparison across different fee structures. A 1.5% per month simple fee has an EAR of 18%, while the same rate compounded monthly results in an EAR of 19.56%.
• Day-by-Day Accrual Table: A detailed breakdown showing how the late fee accumulates day by day, including the fee added each day, the running total fee, and the cumulative amount due. This provides full transparency into the fee calculation over the entire overdue period.

The invoice late payment fee calculator is 100% free with no signup required. All calculations are performed locally in your browser - your invoice amounts, fee rates, and overdue periods never leave your device. There are no file size limits or usage caps. The tool supports preset rates for UK statutory (8% + BoE base rate), EU statutory interest, and US common (1.5%/month) late payment standards, plus custom configuration for any fee structure. Use it as many times as you need to calculate late fees, model different scenarios, or prepare for payment dispute resolution.