Free Invoice Due Date and Late Fee Calculator
"Net 30" means payment is due 30 calendar days after the invoice date. Enter your invoice date and terms below to get the exact due date. Add the amount and the late fee written in your terms to see how late an invoice is and what fee those terms allow.
It runs in your browser. Nothing you type is saved or sent anywhere. The numbers filled in below are a made-up example; change them to yours.
Late fee in your terms:
How the math works
- Due date = invoice date + the number of days in your terms. Net 30 counts calendar days, weekends included.
- Days late = days from the due date to the check date.
- Percent late fee here = amount × percent × each 30-day period (or part of one) after the due date and any grace period. A flat fee is added once.
Example (made up): a $1,200 invoice dated Oct 1, 2026 on Net 30 is due Oct 31, 2026. On Nov 20 it's 20 days late. With a 1.5% monthly late fee, the terms allow $18.00, so $1,218.00 is owed.
Only charge a late fee that was in your terms or contract before you did the work, and check your local rules, since some places cap late fees. A friendly reminder often gets paid faster than a fee. This is general information, not legal or financial advice.
Track every invoice and due date
The Freelancer Invoice Tracker ($9) is a printable invoice plus a client and payment tracker in one spreadsheet: the invoice log marks each invoice Paid, Open or Overdue with days late and totals what each client has paid. It doesn't send invoices or take payments. Works in Excel and Google Sheets.
Get the tracker on Gumroad – $9
This template is also in the Self-Employed & Small Business Bundle (what's inside): all 9 business tools for $29 (about $80 if bought one by one).
We make this template, so take that into account. The calculator above is free to use either way.
Related free guides
- Invoice Payment Terms Explained: Net 15, Net 30 and More
- How to Follow Up on a Late Invoice (Example Numbers)
- How to Track Freelance Invoices So Clients Pay on Time
- What to Put on a Freelance Invoice (Checklist + Example)
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