Late Fees on Invoices: What You Can Charge and How

A late fee is a contractual term. To bind your client it must have been part of the agreement before the work — in the contract, the quote they accepted, or terms they were given and accepted at the outset. Printing it on the invoice alone means introducing a term after the deal was struck, and that generally does not stick.

Where a statutory right to interest exists, this matters less, because that right applies whether or not anything was agreed. Outside those regimes, the contract is the whole of your entitlement.

The second universal principle is that a late charge should compensate rather than punish. Courts across many jurisdictions will strike down a charge that functions as a penalty — set far above any plausible cost of being kept out of your money — while upholding one that reasonably reflects the cost of late payment. A rate anchored to a recognised benchmark is far more defensible than a round number chosen because it sounded discouraging.

For commercial debts between businesses, and for public sector customers, the Late Payment of Commercial Debts (Interest) Act 1998 gives a supplier a statutory right to interest and compensation. It applies automatically — no clause required — although a contract may provide its own substantial remedy instead.

Statutory interest runs at 8 percentage points above the Bank of England base rate. The reference rate is fixed in six-month blocks: for debts becoming late between 1 January and 30 June you use the base rate as at the previous 31 December, and for debts becoming late between 1 July and 31 December you use the rate as at 30 June. Interest runs from the first day the payment was late until it is paid.

On top of interest, there is fixed compensation per overdue invoice, tiered by the size of the debt:

The EU operates a similar regime under the Late Payment Directive (2011/7/EU), implemented through each member state’s own law. It entitles a creditor in a business-to-business transaction to statutory interest of at least 8 percentage points above the European Central Bank reference rate, plus a minimum flat compensation of €40 per overdue invoice — payable automatically from the moment payment is late, with no reminder required.

Two details matter in practice. The reference rate is republished twice a year, taking effect on 1 January and 1 July, so the applicable rate depends on which half-year the debt fell late in — check the currently published figure rather than relying on a number quoted in an article, including this one. And member states may exceed the minimum: Germany applies a higher margin for business-to-business transactions than the Directive floor, and France higher still.

The Directive also constrains how long payment terms can be. Business-to-business terms beyond a set period are permitted only where expressly agreed and not grossly unfair to the creditor, and public authorities are held to tighter limits. A client insisting on very long terms may be on weaker ground than they assume.

There is no federal equivalent. In the US, your right to charge a late fee comes from the contract, which makes the agree-it-first rule decisive rather than merely advisable.

The constraint is state law. Usury statutes cap the interest that may be charged, the caps vary considerably between states, and some states regulate late charges on particular transaction types specifically. A rate that is unremarkable in one state can be unenforceable in another, and the governing law is the state named in the contract rather than necessarily where you are based.

Common commercial practice sits around 1% to 1.5% per month, which is 12% to 18% annualised. That range is widely used, but it is a convention rather than a safe harbour: confirm it against the governing state’s cap before adopting it, particularly at the upper end or when billing consumers, who typically enjoy additional protection.

Effective wording states four things: when a payment becomes late, the rate and how it is calculated, how often it compounds if it compounds at all, and any grace period. Something along the lines of "Invoices unpaid 30 days after the invoice date accrue interest at 1.5% per month on the outstanding balance, calculated daily from the due date" is clear enough that both sides compute the same answer.

A grace period of a few days is worth including. It absorbs bank timing and payment-run mechanics, which prevents the fee triggering on clients who did nothing wrong — and it makes the charge more defensible when you do apply it, because it demonstrates the fee targets genuine lateness.

The strategic point is that late fees rarely earn much money. Their value is as a signal that terms are real, and that value comes almost entirely from consistency. Applying the fee sometimes, to some clients, teaches clients it is negotiable. Many businesses find the better play is to charge it reliably and then waive it explicitly as a goodwill gesture — the fee has done its work either way, and an explicit waiver is worth more than silence.