Calculate late fees and interest penalties on overdue invoices with flat fees, percentage-based charges, and compounding options.
Use the invoice principal and the creditor's stated charge terms to estimate what an overdue balance has grown to. The calculator can combine a fixed late fee with a percentage charge, then apply interest across the overdue interval using the selected compounding treatment. This is useful when an invoice policy contains more than one penalty component. The common mistake is confusing a one-time percentage fee with periodic interest: the first is a distinct charge, while the second depends on elapsed periods and can grow through compounding.
Treat each charge according to its own basis. A flat fee contributes the entered currency amount rather than scaling with the invoice. A percentage-based fee applies the entered percentage to the relevant invoice balance. When both are included, the fixed and percentage components are combined. Keep the original principal distinct from the added penalties when checking the resulting amount due.
Compounded interest grows over repeated periods rather than by simply multiplying the full rate by the overdue count. For principal P, periodic rate r, and n compounding periods, the general relationship is P x (1 + r)^n; the interest is the compounded balance minus P. The selected compounding frequency determines both r and n, so their time units must agree.
No. The result is an arithmetic estimate based on the terms entered. Whether a late fee or interest charge is permitted, capped, disclosed correctly, or triggered at all depends on the contract and applicable law. Confirm the governing terms, grace period, notices, and jurisdiction before using the figure on a demand or statement. Federal agency payments have separate Prompt Payment rules that do not govern private invoices.
Compounding adds interest to a balance repeatedly, so later periods can include interest on earlier interest. A percentage late fee is ordinarily a distinct charge applied to its stated base. The figures match only in special cases. Check whether the entered rate is annual, monthly, or per period, and whether the calculator's compounding interval uses that same time basis.
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