Late Fee Calculator

What to charge when an invoice goes unpaid

Late payment is one of the most common — and most draining — parts of freelancing. A late fee does two jobs: it compensates you for the delay, and it gives clients a reason to prioritize your invoice over the ones without teeth. This calculator works out the fee and the new balance due, whether you charge a percentage per month or a flat amount.

Enter the invoice amount, how late it is, and either your monthly percentage or a flat fee. The tool converts days into months (days ÷ 30), applies the fee, and shows the updated total the client owes.

How much can you charge?

A typical freelance late fee is 1% to 1.5% of the invoice per month — roughly 12% to 18% a year. That's enough to matter without being punitive. Some states cap the maximum interest you can charge on overdue commercial invoices, so keep your rate reasonable and check your state's limit before setting anything higher.

Percentage or flat fee is your call. A percentage scales with the invoice and keeps growing the longer payment is late, which builds urgency on larger jobs. A flat fee is simple and predictable, which suits small fixed-price work. Set a flat fee in the tool and it overrides the percentage.

The rule that makes a late fee stick

Here's the part freelancers miss: a late fee is only enforceable if it was agreed in advance. Put it in your signed contract, and restate it on the original invoice ("Payments over 30 days late accrue a 1.5% monthly fee"). Tacking a fee onto an overdue invoice when the client never agreed to one is difficult to collect and can damage the relationship. Set the terms up front and you're simply enforcing what was agreed.

Actually collecting it

The fee is leverage; collection is process. When an invoice goes past due:

1. Send a polite, firm reminder that references your agreed terms and shows the new balance including the fee. 2. Follow up on a schedule — a few days after the due date, then weekly. Consistent, documented follow-up collects most late invoices. 3. For persistent non-payment, escalate to a formal demand letter and, if needed, small-claims court. Your contract and dated invoices are your evidence.

Automating reminders (many invoicing tools do this) removes the awkwardness and keeps the pressure steady without you having to send every nudge by hand.

What this is

A general contracting utility, not legal advice. Late fees are enforceable only when agreed in advance, and some states cap the rate you can charge — confirm your contract terms and local law before applying a fee.