Accountants Late Payment Interest (Hourly) Calculator
Estimate simple late payment interest on an unpaid accountancy invoice using an annual interest rate and the exact number of overdue hours.
Overview
Use this Accountants Late Payment Interest (Hourly) Calculator to estimate simple interest on an unpaid accountancy invoice. Enter the outstanding amount, annual interest rate, and the overdue period in complete days plus extra hours to see the interest accrued and estimated total due.
How it works
The calculator first converts the overdue period into total hours. It converts the annual interest rate into an hourly simple-interest rate by dividing it by 365 days and 24 hours. It then multiplies that hourly rate by the outstanding invoice balance and total overdue hours. The result is added to the invoice balance to estimate the total amount due.
How to use this calculator
- 1Enter the unpaid invoice balance.
- 2Enter the annual late payment interest rate that applies.
- 3Add the number of complete overdue days.
- 4Enter any additional overdue hours.
- 5Review the estimated interest and total amount due.
Example Calculation
Outstanding invoice amount
$1,000
Annual late payment interest rate
8%
Complete overdue days
30
Additional overdue hours
0
Estimated late payment interest
$6.58
At an annual simple interest rate of 8%, a £1,000 invoice overdue by 30 days accrues an estimated £6.58 in interest, for an estimated total of £1,006.58.
Frequently asked questions
How is hourly late payment interest calculated?
The outstanding balance is multiplied by the annual interest rate converted to an hourly rate, then multiplied by the total number of overdue hours.
Does this calculator use simple or compound interest?
It uses simple interest. Interest is calculated only on the original outstanding invoice balance, not on previously accrued interest.
Why does the calculator use 365 days?
It converts the annual rate using a standard 365-day year. A contract or applicable rule may specify a different convention.
Can I use this calculator for a partially paid invoice?
Yes, enter only the unpaid balance for the period being calculated. If the balance changed during the overdue period, calculate each period separately.
Are fixed late-payment charges included?
No. The result covers interest only and does not include fixed compensation, collection costs, administrative fees, or court costs.
When does late payment interest start?
The start date depends on the payment terms, contract, invoice date, and applicable rules. Check the relevant agreement and local requirements.
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Assumptions and warnings
Assumptions
- The calculation uses simple interest rather than compound interest.
- The annual rate is divided by 365 days and 24 hours per day.
- Interest is calculated on the outstanding invoice amount only.
- The calculation does not include fixed compensation, debt recovery charges, VAT treatment, partial payments, or court costs.
- Results are estimates and may need adjustment for the contract terms and applicable law.
Warnings
- This calculator provides an estimate only and is not legal, financial, or tax advice.
- Late payment interest rules, contractual rates, start dates, and recoverable charges can vary by jurisdiction and agreement.