Late fee math makes the percent, flat, and per-day pieces visible before you send an updated total.

Total late fee: $85.00
Updated total due: $1,285.00
Daily penalty: $0.00

Percent late fee
$60.00
Flat late fee
$25.00
Days late
10

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Late Fee Calculator

Use this when an overdue invoice needs an updated total with late-payment charges.

This calculator keeps one-time and per-day penalties visible so overdue invoice follow-up is easier to explain.

How to use this page

Start with your best current estimate, adjust the inputs until the result feels realistic, and use the related tools below when you want to pressure-test price, profit, or payout from another angle.

Estimate a late fee from one invoice amount, a late fee rate, and any flat or daily penalty.

Use the calculator with the examples below to test ideas quickly and come back to the same setup later.

Worked examples

Start from a realistic scenario

Each example opens the same calculator with shareable URL state.

Overdue invoice

An overdue invoice with a one-time late fee and flat penalty.

$85.00total late fee

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FAQ

Quick answers

Short answers for the questions that usually come up first.

Why include both flat and daily late fees?

Because some payment policies use a one-time penalty plus a continuing daily charge after the due date.

Does this replace contract or legal review?

No. It is only a quick estimate of the math once the late-fee structure is already known.