Can You Charge Late Payment Interest If Your Invoice Has No Due Date?

Guides · Updated October 2026

Can you charge late payment interest if your invoice has no due date? Probably not on that invoice, and I know that is not the answer you wanted. Here is the problem in one sentence: interest needs a starting line. Late means late relative to a date, and if no date was ever agreed, there is no moment when the payment crossed from on time to overdue. A client who never agreed to a due date, and never agreed to an interest rate, can reasonably say they owe you the invoice amount and nothing more. You can still ask. You can still negotiate. But adding interest to that invoice and expecting it to stick is a weak hand, and weak hands get ignored.

This comes up constantly with freelancers and small firms, because the invoice usually gets written in a hurry at the end of a job. The work is done, the client is happy, and the invoice goes out with an amount and a thank you, but no "due within 30 days" and no interest line. Months pass. The client pays slowly or not at all. Then the freelancer discovers late payment interest, runs the calculator, and wants to add three months of charges to the balance. The instinct is understandable. The timing is the problem. Interest terms have to exist before the payment is late, not after you get annoyed.

There are two exceptions worth checking before you give up. The first is your contract. If your contract, proposal, or terms of service say invoices are due within 30 days and carry interest at 1.5 percent per month after that, the invoice itself does not need to repeat the date. The contract controls, and the invoice is just the bill under it. Dig out the signed agreement before you decide you have no terms. The second exception is state law. Some states set a default interest rate for contract claims, often somewhere in the 5 to 15 percent per year range depending on the state and the type of claim. That is not the same as a clean contractual right to charge interest, and using it usually means a demand letter or a small claims filing, not a line you add to the invoice and hope for the best.

Can you charge late payment interest if your invoice has no due date? What to do instead

For the invoice already sent, the practical move is a demand with a deadline, not a surprise interest charge. Write to the client, state the amount owed, and give a specific payment date, say 14 days out. State that you will pursue the balance through collections or small claims if it is not paid. Keep the tone businesslike. What you are doing is creating a record that the debt is undisputed and that you asked clearly, which is worth more than an interest line the client will dispute. If the client offers partial payment, take it in writing and keep the remainder documented.

For the next invoice, the fix costs one line. Put the due date on the invoice itself, even if the contract already has one, and put the interest term right under it: "Due within 30 days. Balances unpaid after the due date accrue interest at 1.5 percent per month." That sentence does three jobs. It sets the date, it sets the rate, and it proves the client saw both before the payment was late. If the client pushes back on the term, that conversation happens before the work, when you still have leverage, instead of after the work, when you do not.

My opinion on rates, since people always ask: 1.5 percent per month is the standard small business figure for a reason. It is high enough to make slow payment cost something, and low enough that most clients will not call it punitive. Rates of 2 percent and above invite a dispute about reasonableness, and some states cap what you can charge regardless of what the contract says. Check your state's ceiling before you write a rate into your template, and never copy a rate from a blog post, including this one, without checking it against your own jurisdiction. This article is general information, not legal advice, and the state variation here is real.

One question I cannot answer for you, and I will leave it standing rather than pretend otherwise: whether your state's default rate applies to your specific invoice, given your contract, your client type, and how the debt arose. That depends on facts no article can see. If the amount is large enough to matter, a short consultation with a local attorney will cost less than the interest you are trying to recover. If the amount is small, the demand letter and the fixed template for next time are the right spend.

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Related: Late Payment Interest Clause for Your Contract · Charging Late Payment Interest With No Contract · What Is a Reasonable Late Payment Interest Rate?

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