How should a small business charge late fees on invoices?

Start with clear payment terms

A late fee works best as part of a complete payment policy. State the due date or term—such as due on receipt, Net 15 or Net 30—and explain what happens after that date. A customer should not discover the fee for the first time after the invoice is overdue.

Choose a fee structure you can explain

Businesses commonly consider either a flat late fee or a percentage-based charge. The right structure depends on the size and frequency of your invoices, customer relationships, contracts and applicable law. Avoid copying another company's percentage without checking whether it fits your business.

Put the policy in more than one place

Include payment terms in the proposal, estimate or service agreement when practical, then repeat them on the invoice. Clear written terms reduce arguments about what the customer agreed to.

Send a reminder before escalating

A missed invoice is not always a refusal to pay. A useful sequence is a friendly reminder shortly before or after the due date, a second notice stating the overdue balance and applicable fee, then a firmer collection step if needed.

Do not let late fees replace good cash-flow practices

For larger jobs, deposits and progress billing may reduce the amount left exposed at the end. For smaller jobs, shorter terms can keep receivables from aging for weeks.

Track what is actually outstanding

Keep the original invoice amount, payments, credits, fees and current balance separate. That makes customer communication cleaner and helps you see whether slow payment is becoming a pattern.

Related: choosing payment terms and improving small-business cash flow.