Invoice Late Fee Calculator.
A $1,500 invoice that is 60 days overdue at 1.5 percent per month carries a $45 late fee. Enter the invoice amount, how late it is and your late fee terms to get the charge, the new total and ready-to-paste wording for your invoice.
Simple (non-compounding) interest. General information, not legal advice: outside the UK statutory scheme, a late fee is normally enforceable only if the customer agreed to it, and some places cap the amount. Runs in your browser.
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Start freeLate Fee Calculator is a free online tool from Neweb (neweb.ai) for small businesses, with no sign-up. A $1,500 invoice that is 60 days overdue at 1.5 percent per month carries a $45 late fee. Enter the invoice amount, how late it is and your late fee terms to get the charge, the new total and ready-to-paste wording for your invoice.
| Cost | Free, no account, no sign-up |
|---|---|
| Built for | Freelancers and consultants and other small businesses |
| Made by | Neweb, the AI website builder and online presence manager (free plan; paid plans from $9/month billed yearly) |
Facts checked October 2026.
What you'll get.
A real example of what this tool produces. Run it above with your own inputs.
A late fee is the extra amount a customer owes when an invoice is paid after its due date. Businesses charge it in one of three ways: a flat amount, a percentage of the invoice for each month it is overdue, or interest at an annual rate that builds up daily. This calculator handles all three, plus the UK's statutory interest scheme for business-to-business debts, and writes the wording to put on your invoice.
Enter the invoice amount and how many days late it is (or pick the two dates), choose your late fee type and rate, and you get the charge, the daily accrual, the new total and two pieces of text: a late fee clause for future invoices and a line for the reminder you send now.
UK statutory late payment interest, as of November 2026
In the UK a business can claim statutory interest from another business on a late commercial payment even if the contract says nothing about it. The rate is 8 percent plus the Bank of England base rate. Bank Rate has been 4 percent since 5 November 2026, so the statutory rate is 12 percent a year. If no payment date was agreed, a payment is late 30 days after the customer gets the invoice or the goods or service is delivered, whichever is later. You can also claim a fixed sum for debt recovery costs, once per late payment:
| Amount of debt | Fixed compensation |
|---|---|
| Up to £999.99 | £40 |
| £1,000 to £9,999.99 | £70 |
| £10,000 or more | £100 |
Sources: gov.uk, Late commercial payments: charging interest and debt recovery and the Bank of England Bank Rate page. Both rate fields are editable in the calculator for when Bank Rate changes.
The formula
Percentage per month: invoice amount × monthly rate × months overdue, where months are days ÷ 30, whole months only, or every started month, as you choose.
Annual rate charged daily (including UK statutory): invoice amount × annual rate ÷ 365 × days overdue.
Flat fee: the fee is added once the invoice is at least one day overdue. In every case the interest is simple, not compounded, and total due = invoice + late fee or interest + any fixed compensation.
How to use the late fee calculator
Enter the overdue invoice amount and pick the currency.
Choose the late fee type: percentage per month, flat fee, annual interest charged daily, or UK statutory interest.
Enter your rate or fee. For UK statutory interest the 8 percent and the current base rate are prefilled.
Type the days overdue, or select the due date and the date you are calculating to and the days fill in automatically.
Set your normal payment terms in days so the clause reads correctly.
Copy the late fee clause onto future invoices and the line onto the reminder or revised invoice.
Tips for better results
- Agree it first. Outside statutory schemes, a late fee generally holds up only if it was in the contract, quote or invoice terms the customer accepted before the work.
- Keep the rate reasonable. Many places limit late fees or interest on commercial or consumer debts, so check the rules where you and your customer are.
- State the due date as a date, not just "30 days", so nobody argues about when the clock started.
- Send a polite reminder before the due date and another the day after. Most late payments are forgotten invoices.
- When you add interest to money owed in the UK, send a new invoice showing it, as gov.uk advises.
- Create the invoice itself with the free invoice generator and paste the clause into its notes.
Example
A real-world walkthrough
A web developer's $1,500 invoice was due on 1 March and is still unpaid on 30 April, 60 days later. Her terms charge 1.5 percent per month, counted by the day. The calculator shows interest of $45.00 (1.5 percent × 2 months × $1,500), accruing at $0.75 a day, and a total now due of $1,545.00. It also gives her the line "Late payment interest: 60 days overdue at 1.5% per month on $1,500.00 = $45.00. Total now due: $1,545.00."
A Manchester print shop is owed £2,000 by another business, 45 days late, with no late fee in the contract. Using UK statutory interest at 12 percent (8 percent plus Bank Rate of 4 percent), the interest is £2,000 × 12% ÷ 365 × 45 = £29.59, plus £70.00 fixed compensation for a debt between £1,000 and £9,999.99. Total now due: £2,099.59.
Frequently asked questions
How do I calculate a late fee on an invoice?
For a monthly percentage, multiply the invoice amount by the monthly rate and by the number of months overdue: $1,500 × 1.5% × 2 months = $45. For an annual rate, multiply the amount by the rate, divide by 365 and multiply by the days overdue: £2,000 × 12% ÷ 365 × 45 days = £29.59. A flat fee is simply added once the invoice is overdue.
What is a typical late fee percentage?
Small businesses commonly charge between 1 and 2 percent of the overdue balance per month, which is 12 to 24 percent a year, or a flat fee on smaller invoices. What you may charge depends on your contract and on local law, which in some places sets a maximum. The rate fields here are yours to set; the calculator does not recommend one.
What is the UK statutory interest rate on late payments?
It is 8 percent plus the Bank of England base rate for business-to-business transactions. With Bank Rate at 4 percent since 5 November 2026, the statutory rate is 12 percent a year as of November 2026. You can also claim fixed compensation of £40 on debts up to £999.99, £70 from £1,000 to £9,999.99 and £100 on £10,000 or more. It does not apply if your contract sets a different interest rate.
Can I charge a late fee if it was not on the invoice?
Usually only where the law gives you the right, as the UK does for business-to-business debts. Elsewhere, a late fee generally needs to be part of the terms the customer agreed to before the sale. If it was not, add the clause to your future quotes, contracts and invoices and apply it from then on. This is general information, not legal advice.
What should late fee wording on an invoice say?
It should state when payment is due, what is charged if it is late, how it is calculated and that it runs until payment. For example: "Payment is due within 30 days of the invoice date. Overdue balances are charged interest at 1.5% per month, calculated daily on a 30-day month, until paid in full." The calculator writes this clause from the options you choose.
Does the calculator compound interest?
No. It uses simple interest on the original invoice amount, which is how most invoice late fees and UK statutory interest are worked out. If your contract compounds monthly, the true figure will be slightly higher for debts overdue longer than a month.
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