100% Free Online Tool

B2B Invoice Late Fee & Interest Calculator

Calculate legally enforceable late payment interest and overdue penalties on unpaid commercial invoices. Generates compliant formal demand notices for accounts payable.

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How to Use B2B Invoice Late Fee & Interest Calculator

Step 1
Enter Invoice Amount
Type the original invoice balance and days past due.
Step 2
Set Penalty Terms
Choose standard contractual interest (e.g. 1.5%/month) or statutory rates.
Step 3
Generate Demand Letter
Copy the updated balance and formal payment demand notice.

Key Features

  • Statutory Interest Models: Supports standard commercial 18% APR and UK statutory late payment interest.
  • Formal Notice Generator: Instant copy-pasteable overdue demand letter for accounts payable teams.

Frequently Asked Questions

Can I legally charge late fees on unpaid B2B invoices?

Yes, provided your contract terms or purchase agreement state late payment terms, or through statutory commercial late payment legislation.