Freelance Finance
Late Payment Interest Calculator
Calculate overdue days, grace-period impact, invoice interest, recovery fees, and the total amount due.
Total late-payment charge
£6.75
29 chargeable overdue days.
- Invoice amount
- £1,000.00
- Daily interest amount
- £0.23
- Interest accrued
- £6.75
- Fixed recovery fee
- £0.00
- Total amount due
- £1,006.75
- Overdue days
- 29
- Grace period
- 0
How to use this calculator
Enter the invoice amount, due date, payment or calculation date, annual interest rate, grace period, optional fee, and compounding method. If payment is early, on time, or still inside the grace period, interest is zero.
Methodology
The calculator counts calendar days from the due date to the payment or calculation date, subtracts any grace period, then applies simple or daily-compounded interest.
Formula
simple_interest = principal * annual_rate * overdue_days / 365
daily_compound = principal * ((1 + annual_rate / 365) ^ overdue_days - 1)Example
A £1,000 invoice at 8.5% annual interest that is 30 days overdue produces £6.99 of simple interest before any fixed recovery fee.
Important considerations
Contracts can replace statutory defaults, consumer debts may be treated differently, and public authority rules can differ. Keep evidence of payment terms and due dates.
FAQs
Does this handle leap years?
Yes. Date differences are counted by actual calendar days, while the annual interest denominator remains 365 as requested.
Can I use this for legal enforcement?
Use it only as arithmetic support. Ask a qualified professional before claiming interest or fees.
Related tools
Freelance Invoice Generator, Project Pricing Calculator, and VAT Calculator UK.
Disclaimer
This calculator does not provide legal advice and does not confirm that a late-payment charge is enforceable.