Estimate the extra amount due on an overdue invoice. Switch between a flat fee, a one-time percentage, or a recurring monthly penalty to match your payment terms.
Calculator
Results update as you edit the fields.
A one-time late fee applies once the grace period ends.
Model multiple fee styles without using a spreadsheet.
Show the total amount due before you send a reminder.
Use the example language below to explain the charge.
Insight
Use the late fee calculator after your invoice is officially overdue and after any grace period in your contract has passed. It helps you quote the charge consistently instead of improvising an amount in email.
Consistency matters because collection friction often comes from surprise, not from the amount itself. If your policy is stable and documented, clients are less likely to argue over the math.
Insight
A flat fee is simple and works well when invoice sizes are similar. A one-time percentage works well when you want the penalty to scale with the invoice amount. A monthly percentage is useful when you want overdue balances to keep getting more expensive over time.
If you invoice both small and large projects, many teams start with a grace period and then apply one consistent percentage rule across all clients.
Insight
Your invoice is now past due under the payment terms agreed in our proposal. As outlined in our billing terms, a late fee has been added to the outstanding balance. The updated amount due is shown below.
Keep your wording factual and calm. You do not need a dramatic collections tone for most first notices.
FAQ
Only if your contract, proposal, or invoice terms allow it, and only if the fee complies with the rules that apply to your state, country, and industry. Use this calculator for planning and communication, not as legal advice.
Flat fees are easier to explain on small invoices. Percentage fees scale better on large invoices. If your invoice sizes vary a lot, a grace period followed by one percentage rule is usually easier to defend.
Yes. Show the original balance, the late fee, and the updated total due so the client can see exactly what changed and pay without back-and-forth.
Related pages
Go straight to the next page that helps with the same billing issue.