Late Payment Penalty Calculator

Calculator Inputs

Responsive grid: three columns on large screens, two on smaller, one on mobile.

Invoice amount

Total billed amount in the contract.

Amount paid

Optional partial payment already received.

Currency

Formatting for totals and exports.

Due date

Payment date

Use today if payment arrives now.

Grace period (days)

Days ignored before penalties begin.

Penalty type

Choose the rule written in your contract.

Annual rate (%)

Used for percent-based penalties.

Daily fee (amount)

Used for fixed daily fee penalties.

Flat fee (amount)

Used for one-time or hybrid penalties.

Compounding frequency

Only used for compounded penalties.

Day-count basis

Some agreements use a 360-day year.

Minimum penalty (amount)

Optional minimum applied when late.

Maximum cap

Optional limit to prevent runaway totals.

Cap value

Use percent if you selected percent cap.

Rounding

Choose how the penalty amount is rounded.

Results appear above this form after submission.

Example Data Table

Sample scenarios showing how different rules change the outcome.

Scenario	Type	Invoice	Paid	Due	Paid on	Charged days late	Penalty	Total due
Example 1	simple	$1,200.00	$0.00	2026-01-10	2026-01-25	12	$3.95	$1,203.95
Example 2	hybrid	$4,500.00	$500.00	2026-02-01	2026-02-20	14	$93.41	$4,093.41
Example 3	daily_fee	$800.00	$0.00	2026-02-05	2026-02-15	10	$60.00	$860.00

Examples use USD for consistent comparison.

Formula Used

The calculator first finds the charged late days: LateDays = max(0, DaysBetween(DueDate, PaymentDate) - GraceDays). Then it applies the selected penalty rule and optional limits.

Simple percent per year: Penalty = Outstanding * (Rate/100) * (LateDays/BasisDays)
Compounded percent: Penalty = Outstanding * ((1+Rate/CompPerYear)^(LateDays/(BasisDays/CompPerYear)) - 1)
Fixed daily fee: Penalty = LateDays * DailyFee
Flat fee: Penalty = FlatFee (only if late)
Hybrid: Penalty = FlatFee + SimplePercentPenalty

Optional limits: Penalty = max(Penalty, Minimum), then cap it using either a fixed amount or a percent of outstanding. Finally apply your rounding preference.

How to Use This Calculator

Enter the invoice amount and any partial amount already paid.
Choose the due date and the payment date you want to evaluate.
Set any grace days allowed in your agreement.
Select the penalty type that matches your document wording.
Fill in rate, daily fee, or flat fee fields as needed.
Add an optional minimum or cap if your terms specify one.
Press calculate to see penalty and total due above.
Use CSV or PDF buttons to save the summary.

This tool supports planning and documentation. For enforceability, verify terms with your signed agreement and applicable law.

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