Payment Delay Cost Calculator

Calculator Inputs

Currency Symbol

Used across result cards, exports, and tables.

Invoice Amount

Original billed amount before deductions.

Prepaid Amount

Amount settled before the due date.

Credit Adjustments

Credit notes, deductions, or approved offsets.

Due Date

Contractual payment deadline.

Payment Date

Actual settlement date for the delayed payment.

Grace Days

Allowed delay days before charges begin.

Contract Interest Rate (%)

Annual contractual late-payment rate.

Internal Carrying Cost Rate (%)

Annual internal financing or cash-hold cost.

Tax On Charges (%)

Applied to interest, fees, and carrying cost.

Fixed Late Fee

One-time contractual late fee.

Admin Fee

Processing, file handling, or legal admin charge.

Reminder Fee

Charge for notices and follow-up reminders.

Collection Cost

External recovery or collection expense.

Interest Method

Matches different contract language styles.

Day Count Basis

Controls annual-rate conversion into delay-period charges.

Example Data Table

Scenario	Outstanding Principal	Effective Delay Days	Method	Interest	Fees	Tax	Total Delay Cost
Office lease invoice	$20,000.00	40	Simple Daily	$263.01	$200.00	$24.15	$507.16
Equipment supply contract	$48,000.00	22	Compound Daily	$347.78	$350.00	$41.87	$739.65
Consulting milestone payment	$12,500.00	65	Flat Monthly	$375.00	$160.00	$32.10	$567.10

Formula Used

Outstanding Principal = Invoice Amount − Prepaid Amount − Credit Adjustments

Raw Days Overdue = Payment Date − Due Date

Effective Delay Days = max(Raw Days Overdue − Grace Days, 0)

Simple Daily Interest = Outstanding Principal × Annual Contract Rate × (Effective Delay Days ÷ Day Count Basis)

Compound Daily Interest = Outstanding Principal × [(1 + Annual Contract Rate ÷ Day Count Basis)^{Effective Delay Days} − 1]

Compound Monthly Interest = Outstanding Principal × [(1 + Annual Contract Rate ÷ 12)^{Effective Delay Days ÷ 30} − 1]

Flat Monthly Interest = Outstanding Principal × (Annual Contract Rate ÷ 12) × Ceiling(Effective Delay Days ÷ 30)

Carrying Cost = Outstanding Principal × Annual Carrying Cost Rate × (Effective Delay Days ÷ Day Count Basis)

Fees Before Tax = Fixed Late Fee + Admin Fee + Reminder Fee + Collection Cost

Tax On Charges = (Interest + Carrying Cost + Fees Before Tax) × Tax Rate

Total Delay Cost = Interest + Carrying Cost + Fees Before Tax + Tax On Charges

Total Payable = Outstanding Principal + Total Delay Cost

How to Use This Calculator

Enter the invoice amount and subtract any advance payment or credit note.
Choose the due date and the actual payment date.
Set grace days if your contract allows a no-charge period.
Enter the annual contract rate and any internal carrying cost rate.
Add fixed late charges, admin fees, reminder fees, and collection costs.
Select the interest method that matches your agreement wording.
Choose the day-count basis used for rate conversion.
Click the calculate button to view total delay cost, payable amount, and the growth graph.
Download CSV for records or PDF for reporting and claim support.

Frequently Asked Questions

1) What does this calculator measure?

It measures the total financial impact of a late payment. That includes contract interest, internal carrying cost, fixed fees, reminder charges, collection cost, tax on charges, and the final payable amount.

2) Why include carrying cost with late interest?

Late interest reflects contract compensation. Carrying cost reflects your internal funding pressure from delayed cash. Using both shows the external claim value and the internal business burden caused by payment slippage.

3) When should I use simple daily instead of compound daily?

Use simple daily when the contract states an annual rate applied proportionally by days. Use compound daily when the contract or policy allows interest to grow on accumulated interest during the overdue period.

4) What is the purpose of grace days?

Grace days delay the start of penalty charges. They are useful when a contract allows a short buffer after the due date before interest, fees, or default remedies begin.

5) Should tax apply to all charges?

Not always. Some agreements or local rules tax service-related fees, while others exclude pure interest. This calculator applies tax uniformly to charges so you can model a consistent scenario quickly.

6) Can I use this for partial payments?

Yes. Enter any amount already paid before settlement in the prepaid field. Add credit notes in credit adjustments. The calculator then applies delay charges only to the remaining outstanding principal.

7) Why does the graph start above zero sometimes?

If you entered fixed fees, admin charges, reminder fees, or collection cost, those charges exist as soon as the delayed-charge period starts. That is why the cost line may not begin at zero.

8) Is this calculator suitable for legal claims?

It is useful for estimating exposure and preparing support schedules. Final claim wording, tax treatment, recoverability, and enforceability should still be checked against the contract, governing law, and professional advice.