Late Fee Calculator

In percent mode, the late fee is calculated as annual simple interest pro-rated by the number of days overdue. In flat-fee mode, the rate value is applied as a one-time dollar fee regardless of days overdue. The total owed is the original invoice amount plus the late fee. All math runs locally in your browser.

Advisory: Many states cap late-fee/interest rates (usury limits) — check your state's limit and your contract.