Invoice Late Fee Calculator for Small Business

Overdue receivables tying up your cash flow? Work out the late fee, daily accrual, and total now due. No signup, no email.

For a small business, a consistent, documented late-fee policy protects cash flow without souring client relationships. Disclose it at onboarding, show it on every invoice, and apply it the same way every time.

How to charge late fees the right way

A late fee only works if it is agreed in writing before the work starts. You cannot spring a fee on a client after an invoice is already overdue and expect it to hold up. Put the exact terms in your signed contract or engagement letter, repeat them on every invoice, and you turn "please pay me" into a predictable line item clients expect.

The five steps

1. State the policy up front. Put your rate (for example 1.5% per month), the grace period, and when the fee starts into the contract the client signs. 2. Repeat it on the invoice. Show the due date and the late-fee terms on the invoice itself. 3. Send a reminder a few days before the grace period ends — most late payments are simple oversight. 4. Apply the fee as its own line item so the client can see the overdue period, the rate, and the new total. 5. Be consistent. Applying fees to some clients but not others makes the policy feel negotiable.

Percentage or flat fee?

A monthly percentage (1–2% is standard) scales with the invoice size and is easier to defend than a flat $25–$50 charge, which feels heavy on a small invoice and trivial on a large one. The freelancer standard is 1.5% per month, which is 18% per year.

Sample late-fee wording

“Invoices unpaid after the due date incur a late fee of 1.5% per month (or $50, whichever is greater) on the outstanding balance, added monthly until paid in full.” Adapt the numbers to your contract and confirm they are within your state’s limit.

FAQ

Should a small business charge late fees?

A clear, consistently applied late-fee policy improves on-time payment and protects cash flow. The key is disclosing it in the signed agreement before work begins and applying it consistently across clients.

How much can I charge as a late fee on an invoice?

The common business standard is 1% to 1.5% per month (12% to 18% per year) on the overdue balance. The legal ceiling depends on your state and on whether the relationship is commercial or consumer, so confirm your state's limit before setting a rate.

Can I charge a late fee if it wasn't in the contract?

Generally no. Late fees are enforceable only when they were disclosed in a signed agreement or accepted payment terms before the work began. Adding a fee to an invoice that is already overdue is hard to enforce and often disputed.

How is the late fee calculated?

Take the annual interest rate, divide by 365 to get a daily rate, multiply by the invoice amount and by the number of days overdue (after any grace period). Example: $5,000 at 18% per year for 30 days is $73.97.

What is a typical grace period?

Grace periods are a contract term you choose, not usually a state requirement. Five to fifteen days is common. Set it in your agreement and state it on the invoice.

Do I need to send a reminder before applying the fee?

It isn't legally required, but a short reminder a few days before the grace period ends resolves most late payments without friction and reduces disputes.

By state

Interest and late-fee rules vary by state — pick your state for the commonly cited reference. Other audiences: Freelancers · Contractors · Small business.