ChaseOwlLate Fee Calculator for Overdue Invoices
Find out how many days an invoice is overdue and how much late fee you can add. Choose a flat fee or a monthly percentage charged as simple interest, then copy a ready-made line for your invoice or reminder email.
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How the late fee is calculated
- Days overdue is the number of calendar days between the due date and today. Nothing is owed on or before the due date.
- Flat fee: one fixed charge once the invoice is overdue (after any grace period).
- % per month: simple interest, prorated by day. Fee = amount × monthly rate × (chargeable days × 12 ÷ 365). For example, 1.5% per month on $1,000 for 30 days is $14.79. Interest is not compounded.
- Grace period: optional days after the due date before any fee starts.
Before you charge a late fee
Only add a late fee if your contract, proposal or invoice terms said you would, and state the rate up front on every invoice. Many places cap the interest you can charge on overdue business debts, so check the rules where you and your client are based. This calculator is a convenience, not legal or tax advice. For wording, see our late payment email templates.
Let ChaseOwl chase this invoice automatically
Forward the invoice (PDF, Word, PayPal or Wise) and ChaseOwl sends polite, escalating reminders on the due date and at 3, 7 and 14 days late, signed with your name, until you mark it paid. Free for 2 invoices, no card needed.
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- Payment reminder email generator: Write a friendly, firm or final reminder email for an unpaid invoice in seconds, ready to copy and send.
- Free invoice template: Fill in a clean invoice in your browser, then print it or save it as a PDF. No login needed.