Late Payment Fees on B2B Invoices: How to Charge and Collect

Last updated: November 03, 2026

Late payment fees look like the obvious answer to overdue invoices: add a charge, and customers will pay sooner. In practice the clause only works if it is written well, communicated early and enforced with judgment. This guide covers how to decide whether to charge, what you can legally add, how to word the clause, and how to build a follow-up workflow so the fee is a lever rather than a threat you never carry out.

In this guide

• Why late payment fees matter
• What you can charge
• Writing the clause
• When to enforce and when to waive
• A fee-and-follow-up workflow
• Where automation helps
• FAQ

Why late payment fees matter

Late payment is the norm, not the exception. An Upflow report on B2B payments found that 57% of invoices were paid late on average across the industries analysed, and that 33% of overdue invoices were still unpaid 90 days after their due date. A separate compilation of statistics by a collections agency says 56% of US small businesses are owed money from late payments.

If more than half of your invoices arrive late, the cost is not abstract. Every extra week of waiting raises your days sales outstanding, ties up working capital and pushes your team into manual chasing. Our B2B playbook for reducing DSO shows how quickly those delays compound. A late fee is one of several tools that change the customer's incentive, alongside discounts for paying early, which we weighed in is a 2/10 net 30 discount worth it.

What you can charge

There are three common structures, and many companies combine two of them.

Flat fee

A fixed amount per overdue invoice is simple to explain and to calculate. It works well for smaller invoices, where a percentage would be too small to matter. The downside is that it does not grow with the delay, so a customer who is three months late pays the same as one who is three days late.

Percentage or interest

A monthly percentage on the overdue balance scales with both the invoice size and the delay. It is the most common approach for larger B2B invoices and is easy to apply with accounting software. State the rate, how it is calculated and when it starts to accrue.

Statutory interest and compensation

Some jurisdictions give suppliers a right even without a clause. In the UK, the Late Payment of Commercial Debts (Interest) Act entitles a supplier to a fixed sum of £40 for debts under £1,000, £70 for debts from £1,000 to under £10,000, and £100 for debts of £10,000 or more, on top of interest. A law-firm guide describes the interest rate as 8% above the Bank of England base rate. Other countries and US states have different rules, so check the law where you and your customer operate.

Writing the clause

A late fee you cannot point to in a signed document is hard to collect and easy to dispute. Before you rely on one, make sure these elements are in your agreement or order form:

• The payment term in plain language. Say whether the clock starts at the invoice date or the receipt date, and what counts as payment.
• The fee itself. A flat amount, a percentage per month, or both, with a note on whether it compounds.
• The start date. Many companies add a short grace period of a few days so a bank delay does not trigger a charge.
• Collection costs. If you reserve the right to recover reasonable collection costs, say so explicitly.
• The dispute route. Explain how a customer flags a problem with an invoice and what happens to the fee while it is reviewed.

Then repeat the term on every invoice and reminder. Customers rarely reread a contract, but they do read the footer of an invoice. Have your lawyer review the wording, because enforceability depends on jurisdiction.

When to enforce and when to waive

Consistency matters more than severity. If you enforce the fee for one customer and waive it for another without a reason, you invite disputes and weaken the clause for everyone. A simple policy helps your team decide quickly:

• Enforce when the invoice was correct, delivered on time and the customer simply paid late.
• Waive when the delay was caused by your error, a missing purchase order you should have requested, or an invoice that was sent to the wrong contact.
• Pause while a genuine dispute is open. Resolving the underlying issue first is usually faster, as we describe in how to settle invoice disputes faster.
• Trade the fee for a commitment. Offering to drop it in exchange for a firm payment date, or for a structured schedule like the ones in flexible payment plans that recover more B2B debt, often brings cash in sooner than insisting on the full charge.

A fee-and-follow-up workflow

The fee should be the third or fourth step in a sequence, not the first. A workable cadence looks like this:

1. Before the due date. Send a friendly reminder with the invoice, the due date and a payment link. Mention the late fee terms in neutral language.
2. On the due date. A short note confirming the invoice is due today and asking whether anything is blocking payment.
3. A few days after. A personal message that asks for a payment date and checks for disputes. Capturing a date matters; we cover how to make those commitments stick in improving your promise-to-pay kept rate.
4. At the grace-period end. Apply the fee, send an updated statement and explain the charge clearly.
5. Escalation. If silence continues, move the account to a senior contact or a formal collections step.

Review the results regularly. An accounts receivable aging report shows which buckets the fee is moving and which customers ignore every notice, and the collection effectiveness index tells you whether the whole process is working rather than just the fee.

Where automation helps

The hardest part of a late fee policy is not the clause. It is applying the same sequence to hundreds of invoices without your team spending hours on reminders, calls and exceptions. Automated reminders cover the early steps, as shown in automated payment reminders that get invoices paid, and AI-assisted dunning management can adjust tone and timing by account.

That is the gap Rio, Darwin AI's collections agent, is built for: it contacts customers over voice and messaging, asks for a payment date, records the promise and flags disputes or accounts that need a person, so your team handles the exceptions instead of the routine reminders. Whatever tool you use, keep humans in charge of waivers and sensitive accounts.

FAQ

Can I charge a late fee if it isn't in my contract?

Generally you should not count on it. In most places a late fee or interest needs a basis in your signed terms, so put the clause in your master agreement or order form before the first invoice goes out. Rules differ by country and state, so confirm with a lawyer. This article is general information, not legal advice.

How much can I charge in the UK?

Under the UK Late Payment of Commercial Debts (Interest) Act, a supplier is entitled to a fixed sum of £40, £70 or £100 depending on the debt size, in addition to statutory interest, which one law-firm guide describes as 8% above the Bank of England base rate.

Do late fees actually make customers pay faster?

They help most when they are visible before the due date and applied consistently. A fee that is never enforced teaches customers to ignore it, so pair the clause with reminders and a clear escalation path.

Should I waive a late fee?

Yes, selectively. Waive it when the delay was your error, when a genuine dispute is open, or in exchange for a firm payment date. Record every waiver so the exception does not become the rule.