Invoice late fee calculator
Enter an unpaid invoice, how many days late it is, and the late fee in your terms. You get the fee to add, the new balance, what each extra day costs the client, and a line of wording to put on your invoices.
Wording for your invoices
Get the Invoice Tracker Template Google Sheets + Excel, Payment Reminder Email Templates (Word + PDF), $9 one-time. Launch price: 50% off with FIRST10, first 10 buyers.
The % fee is simple interest, pro-rated daily on a 30-day month: amount x monthly rate x days / 30. The flat fee is added once the invoice is a day late. A late fee is only enforceable if the client agreed to it before the work started, and many US states cap the rate; in the UK, business invoices can carry statutory interest of 8% a year above the Bank of England base rate instead. This is math, not legal advice.
Stop writing awkward payment chasers
The Invoice Tracker Template Google Sheets + Excel, Payment Reminder Email Templates (Word + PDF) has 10 ready-to-send emails from the friendly reminder to the letter before action, payment terms and a late fee policy to add before the work starts, and the Invoice Chaser spreadsheet: it tracks every invoice, works out late fees, tells you who to chase today and writes the email with the client's name, amounts and dates filled in. Word, Google Docs, Excel and Google Sheets. One-time $9.
Get the Invoice Tracker TemplateNeed a custom Excel or Google Sheets tracker built around how you work? I build them on Fiverr, from $5. See the offer on Fiverr
How the late fee is worked out
Most freelancers and small businesses charge a late fee as a monthly percentage of the unpaid balance, often 1.5% a month (18% a year), sometimes with a small flat fee on top. Charging it daily from the due date means the client pays for exactly how late they are, and it gives them a reason to pay today instead of next week.
Late fee = invoice amount x monthly rate x days late / 30 + flat fee
Worked example
A $2,400 invoice is 45 days late. Your terms say 1.5% a month plus a $25 late fee. The percentage part is 2,400 x 0.015 x 45 / 30 = $54.00. Add the $25 flat fee and the late fee is $79.00, so the client now owes $2,479.00. Each extra day adds 2,400 x 0.015 / 30 = $1.20.
With a 15-day grace period the percentage only runs for 30 days: 2,400 x 0.015 x 30 / 30 = $36.00, or $61.00 with the flat fee.
Making a late fee stick
The fee has to be agreed before the work starts. Put it in your contract or proposal, print the wording above on every invoice, and mention it in your reminders from the first overdue email. A fee you add without warning is easy for a client to refuse, and it sours the relationship.
Keep the rate reasonable. In the US the legal maximum depends on your state; some cap late fees or interest well below 18% a year. In the UK, business-to-business invoices carry statutory interest of 8% a year over the Bank of England base rate, plus fixed compensation of £40, £70 or £100 depending on the debt, even if your contract says nothing. In the EU, the Late Payment Directive sets interest at least 8 points over the ECB reference rate plus €40.
The fee is a nudge, not the plan. What gets most invoices paid is a steady sequence of short, polite emails that ask for a specific payment date. The payment reminder email generator writes the right one for how late the invoice is.
Questions
What is a normal late fee on an invoice?
1% to 1.5% a month on the unpaid balance is common, often with a flat fee of $25 to $50. On a $2,400 invoice 45 days late, 1.5% a month comes to $54.00.
Can I charge a late fee if it wasn't in my contract?
Usually not in the US, unless the client agrees to it. In the UK, business invoices carry statutory interest and fixed compensation even without a clause. Add the fee to your terms before the next project.
Is 1.5% a month the same as 18% a year?
Yes, as simple interest: 1.5% x 12 = 18%. This calculator charges it daily, so 45 days at 1.5% a month is 2.25% of the invoice.
When should the late fee start?
The day after the due date, unless your terms give a grace period. A short grace period of 5 to 7 days avoids charging clients whose payment is already in transit.