Late Payment Interest Calculator

How to Calculate Late Payment Interest

Dealing with unpaid invoices is difficult enough without having to manually compute statutory interest across different legal frameworks. Whether you operate in the UK under the Late Payment of Commercial Debts Act, in the US, or elsewhere, knowing how to correctly calculate late payment interest is essential for fair compensation. Our Late Payment Interest Calculator automates this complex legal math, instantly providing accurate figures for your demand letters and court documents.

What is Statutory Late Payment Interest?

Statutory interest is a legal provision that allows B2B (business-to-business) suppliers to charge interest on excessively late invoices. It serves as a deterrent against late payers and compensates the creditor for the cost of not having that money available. Rates vary wildly by jurisdiction. For instance, the UK enforces a strict "Bank of England Base Rate plus 8%" rule, whereas certain US states rely on a flat statutory rate if no specific contract terms were agreed upon.

• Provides Leverage: Simply threatening to apply statutory interest often prompts immediate payment from sluggish accounting departments.
• Legal Right: In many jurisdictions, you are legally entitled to this interest even if it was not explicitly stated in your original contract.
• Recovers Costs: It helps cover banking fees, overdrafts, and administrative costs caused by your client's delay.

How to Use Our Calculator

Our tool makes interest calculation effortless. Enter the principal invoice amount, the original due date, and your jurisdiction. The calculator instantly determines the number of days the invoice is overdue and computes the legally applicable interest rate (or standard commercial default rate). The live preview updates in real-time, generating a clean, professional summary clause that you can copy-paste directly into your next reminder email, Letter Before Action, or Small Claims filing.

Frequently Asked Questions (FAQ)

Can I charge late payment fees in addition to interest?

It depends entirely on your jurisdiction. In the UK, the law allows you to charge both statutory interest and a fixed debt recovery cost (ranging from £40 to £100 depending on the invoice size). In other areas, such as specific US states, you may be restricted heavily unless it was explicitly written and signed in a master service agreement.

When does an invoice officially become late?

An invoice is considered overdue the day after the agreed payment terms expire. If you did not agree to specific terms, many legal frameworks default to 30 days after the invoice was received by the client or the service was delivered.

Should I actually invoice the client for this interest?

In most real-world scenarios, businesses use the threat of calculating and invoicing late interest as leverage to get the principal amount paid. If the client refuses to pay the principal, the calculated interest is typically bundled into the total amount claimed when filing a lawsuit in a small claims court.