Cash flow · 2026
Late Payment Fee Calculator
Enter the overdue invoice and your contract terms.
Enter only a rate stated in the signed agreement and permitted by applicable law. The default is an example, not a legal recommendation.
- Late fee accrued
- $112.50
- Equivalent annual rate
- 18.0%
- Accruing per day
- $2.50
- Months past due
- 2
Transparent method
How this calculator works
- Convert days late to 30-day months.
- Apply either simple monthly interest or fractional-month compounding to the unpaid invoice.
- Show the accrued fee, daily pace, and total balance.
- Worked example: $5,000 × 1.5% × 1.5 thirty-day months = $112.50 under the simple-interest setting.
What the result does not include
- Your signed contract and applicable law determine whether a fee is enforceable and how it accrues.
- The calculator does not decide statutory interest, collection costs, grace periods, or partial-payment allocation.
Common questions
What does a worked late-fee example look like?
For a $5,000 invoice 45 days late at 1.5% per 30-day month, simple interest is $5,000 × 0.015 × 1.5 = $112.50, so the modeled total is $5,112.50. Confirm signed terms, grace periods, partial payments, and applicable law before using it.
Can I charge a late fee if my contract does not mention one?
Do not assume you can add one after the fact. The contract and applicable state law control whether a fee is allowed and how it must be disclosed. Confirm the rule for your state before relying on this calculation. This is not legal advice.
Do late fees actually get paid?
Often they are waived as a goodwill gesture in exchange for immediate payment — which is exactly their value. The fee is leverage that makes your invoice the one that gets paid first, not a revenue line.