Invoice Late Fee Calculator
An invoice that is 60 days overdue costs you more than patience — it costs the interest you never charged. This calculator turns your late-fee policy into a precise figure: enter the unpaid amount, how many days late it is, and the rate from your payment terms, and you get the fee, the total now due and the daily rate at which it keeps growing. It handles the two ways terms are usually written — a monthly percentage such as 1.5% per month, or an annual percentage — and shows both so you can quote whichever your contract uses. Use it before you send a reminder so the number in your email matches the number in your terms.
Days your terms allow before fees start.
1.5% per month is the common business default.
Late fee
$45.00
Accrued over 45 chargeable days.
- Original balance
- $2,000.00
- Total now due
- $2,045.00
- Cost per additional day
- $1.00
- Effective annual rate
- 18%
Quote this to show the client what waiting costs them.
Late fees are only enforceable if they appear in terms your client agreed to, and maximum rates are capped by local usury law. This is an estimate, not legal advice.
How to use Invoice Late Fee Calculator
- 1
Enter the overdue amount
Type the unpaid invoice balance. If a partial payment was made, use the remaining balance rather than the original total.
- 2
Set the days late and your rate
Enter how many days past due the invoice is, then the rate from your payment terms — for example 1.5% monthly. Add a grace period if your terms include one.
- 3
Read the fee and total due
The calculator shows the late fee, the updated balance and the daily accrual so you can state all three in your reminder.
Why use this tool
- Works with monthly, annual or flat-fee late charges
- Shows the fee, the new balance and the cost per additional day
- Optional grace period so you only charge from the day terms allow
- Compounding option for terms that charge interest on interest
- Runs entirely in your browser — invoice figures are never uploaded
Frequently asked questions
- What is a standard late fee for an invoice?
- The most common business late fee is 1.5% per month on the outstanding balance, which is 18% per year. Rates between 1% and 2% per month are typical. What matters more than the figure is that it appears in the payment terms your client agreed to before the work started.
- How do I calculate a 1.5% monthly late fee?
- Multiply the overdue balance by 0.015 to get one month of interest, then pro-rate it for the actual days late: balance × 0.015 × (days ÷ 30). On a $2,000 invoice 45 days late that is $2,000 × 0.015 × 1.5 = $45. This calculator does the pro-rating for you.
- Is there a legal limit on late fees?
- Yes. Maximum interest rates are set by state or national usury law and vary widely, and some jurisdictions cap what you can charge consumers more tightly than businesses. Check the rules where you operate, or ask a lawyer, before applying a high rate.
- Should I use a flat fee or a percentage?
- A flat fee is simpler to explain and works well on small, similar-sized invoices. A percentage scales fairly across large and small jobs and keeps pressure on a client who is months behind. Some businesses use both: a flat charge at the first missed deadline, then monthly interest after that.
- What is the difference between simple and compound late interest?
- Simple interest is charged only on the original overdue amount. Compound interest is charged on the balance including previously added fees, so it grows faster. Simple interest is the norm for commercial invoices unless your contract explicitly says otherwise.
- Can I charge a late fee if it was not in my contract?
- Generally no — a fee you never disclosed is hard to enforce and damages the client relationship. Add a clear late-payment clause to your terms, invoices and quotes going forward. For the current invoice, a polite reminder is usually the more productive route.
- Do my invoice figures get uploaded anywhere?
- No. The calculation runs in your browser with JavaScript. Nothing you type is transmitted, logged or stored on a server.
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