Late Payment Interest & Fee Calculator
Estimate overdue invoice interest and fees transparently. No signup. Enter your own figures, check the breakdown and save your inputs privately on this device.
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Editable sample valuesYour calculation
Results update as you edit. All amounts in USD unless a field states otherwise.
Not legal advice: interest and late fees must be permitted by your contract and applicable law. This tool does not calculate compound interest.
How to use the late payment interest & fee calculator
Estimate unpaid invoice balances using optional simple annual interest and flat fees. Start by replacing the editable example numbers with your own project, customer or business data. Your result changes immediately, making it easier to compare situations before quoting, budgeting or making operational decisions.
1. Add your real costs
Enter figures from your latest job, client brief, booking, contract or monthly operating budget. Use consistent time periods and units.
2. Review the breakdown
Don't rely only on the main number: examine the supporting costs, deductions and assumptions shown in the results panel.
3. Save for repeat visits
The Save button stores your inputs in this browser only. Return with the same device and browser profile to adjust your numbers next time.
4. Share a simple summary
Copy the calculated breakdown or choose Print / Save PDF for a print-ready copy. Verify your information before sharing it with customers.
Important considerations
Not legal advice: interest and late fees must be permitted by your contract and applicable law. This tool does not calculate compound interest. Use this tool for planning and transparent conversations—not as a substitute for contracts, required records, tax advice or a licensed professional where applicable.
Frequently asked questions
How is simple late payment interest calculated?
A common simple-interest illustration is principal times annual rate times overdue days divided by 365.
Can I charge any late fee I want?
No. Your contract and jurisdiction may restrict late fees and interest. Check before adding charges.
Does this calculate compounded interest?
No. It assumes simple interest with a 365-day year.
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