Invoice late fee calculator
Enter the unpaid amount and the dates, choose how you charge, and see the fee, how many times it applies and the new balance. It handles terms like 1.5% a month or a $25 fee after a grace period.
Late fees owed
$30.00
- Days late
- 45
- Times the fee was added
- 2
- Invoice amount
- $1,000.00
- New balance
- $1,030.00
First fee on day 1 after the due date, then every 30 days.
Watch how it works
Work out the late fee on an overdue invoice, as a percentage, a flat fee or interest.
1:18 · narrated, with on-screen captions
How it's calculated
Days late = paid date − due date
Percentage fee = unpaid amount × fee %, added on day (grace + 1), then every N days
Flat fee = the fixed fee, added on the same schedule
Yearly interest = unpaid amount × yearly rate ÷ 365 × days late after the grace period
New balance = unpaid amount + late fees (never more than the cap)
With the example numbers, a $1,000 invoice paid 45 days late with a 1.5% fee every 30 days and no grace period: the first fee is added on day 1 and the second on day 31, so 2 × $15.00 = $30.00 and a new balance of $1,030.00. Each fee is rounded to the cent.
Tick the compound box and each new percentage is worked out on the balance including earlier late fees: $15.00, then 1.5% of $1,015.00 = $15.23.
How to word a late fee on an invoice
Say exactly when the fee starts, how much it is and whether it repeats. Two examples you can adapt:
- “Payment is due within 30 days. A late fee of 1.5% of the unpaid balance is added every 30 days after the due date.”
- “A $25 late fee applies to payments received more than 15 days after the due date.”
Put the same wording in your quote or contract before you start the work, and repeat it on every invoice, so the fee never comes as a surprise.
Before you charge one
What you may charge depends on your agreement with the client and on the law where you and they are based. States and countries limit late fees and interest in different ways, so check the rules that apply to you before setting a rate.
A friendly reminder a few days before the due date often does more than a fee. Fees work best as the backstop, not the first message the client gets.
Common questions
How do I calculate a late fee on an invoice?
For a percentage fee, multiply the unpaid amount by the percentage: 1.5% of $1,000 is $15. For a flat fee, add the fixed amount. For yearly interest, multiply the amount by the yearly rate, divide by 365 and multiply by the number of days late.
What is the difference between 1.5% a month and 18% a year?
They look the same but are charged differently. On $1,000 that is 30 days late, 1.5% charged once is $15.00, while 18% a year by the day is $1,000 × 0.18 ÷ 365 × 30 = $14.79.
What is the standard late fee on an invoice?
There is no single standard. Businesses use a monthly percentage, a flat fee or daily interest, and what you may charge depends on your agreement with the client and on local law.
What is a grace period?
The number of days after the due date before any fee applies. With a 10-day grace period, the first fee is added on day 11.
Do late fees compound?
Only if your terms say so. By default this calculator works each percentage out on the original unpaid amount; tick the compound box to include earlier late fees in the balance.
Is anything I enter sent or saved?
Nothing is sent anywhere; the math runs in your browser. Your last numbers are kept in this browser so they are there next time, and Reset clears them.
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