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Invoice Late Fee

Late payments are the most common cash flow problem freelancers face. Charging a late fee — and stating it clearly on your invoice — both compensates you for the delay and creates an incentive for clients to pay on time. Our late fee calculator computes the interest due on overdue invoices using either a flat fee, a percentage of the invoice, or a daily compound rate.

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%

Common: 1.5%/mo = 18%/yr

$

Total Late Fee Owed

Days Overdue
Interest Accrued
Flat Fee
Total Amount Due
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About the Invoice Late Fee Calculator

Late payments are the most common cash flow problem freelancers face. Charging a late fee — and stating it clearly on your invoice — both compensates you for the delay and creates an incentive for clients to pay on time. Our late fee calculator computes the interest due on overdue invoices using either a flat fee, a percentage of the invoice, or a daily compound rate.

How to use it

  1. Enter the original invoice amount and the invoice due date.
  2. Enter today's date (or the date you are calculating from).
  3. Choose your late fee method: flat fee, percentage (e.g. 1.5%/month), or daily compound.
  4. See the total amount due including accrued late fees.

Formula & methodology

Flat fee: Total = Invoice + Late fee amount. Monthly %: Total = Invoice × (1 + rate)^months_overdue. Daily compound: Total = Invoice × (1 + annual_rate/365)^days_overdue.

Common use cases

  • Calculating how much a client owes after 45 days past due
  • Sending a revised invoice with late fees added
  • Deciding whether late fees are worth the client relationship risk
  • Setting a late fee policy before signing new client contracts
  • Estimating total collections value on aged receivables

Frequently asked questions

1–1.5% per month (12–18% annually) is standard in the US. Some states cap late fees, so check local regulations. State the rate explicitly in your contract and on every invoice.
Legally it is difficult to enforce late fees that were not agreed upfront. Always include a late fee clause in your contract and repeat it on each invoice so the client cannot claim they were unaware.

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