Late Fees on Contractor Invoices: How to Charge Them and What States Allow

A late fee is not a punishment; it is the price of the credit you extended when you let the invoice go unpaid. Charged correctly it moves slow payers to the front of the queue and costs you nothing in goodwill, because the customer agreed to it in advance. Charged incorrectly, sprung on an invoice after the fact or set above the state limit, it is unenforceable and sometimes a violation. Here is the correct version.

The rule that matters most: agree it before the work

No state lets you add a late fee the customer never agreed to. The fee has to be in the estimate or contract the customer approved, in plain words: the rate, when it starts, and how it is calculated. An invoice is not a contract; a fee that first appears there is a request, not a term. Put the sentence on the estimate, repeat it on every invoice, and mention it once in the reminder before it applies.

How much: the common rate and the state limits

The usual rate on contractor invoices is 1.5% per month on the unpaid balance, which is 18% a year, or a flat fee such as $25 or $50 on smaller invoices. Whether 1.5% is allowed depends on your state. There is no federal cap on late fees between businesses or on consumer service contracts, but state usury and consumer-protection laws set ceilings, and a few states cap the annual rate below 18%. The construction prompt-payment statutes give a useful reference point for what legislatures consider reasonable: Texas and Arizona use 1.5% per month, Pennsylvania and Connecticut 1% per month, Maryland 9% per year.

The safe way to write the clause is to state your rate and cap it at the legal maximum: “Late payments accrue interest at 1.5% per month (18% per year) or the maximum rate permitted by law, whichever is less, beginning 7 days after the due date.” That sentence stays enforceable in a state with a lower ceiling instead of failing entirely.

Percentage or flat fee

• Percentage of the balance: fair across invoice sizes and the norm on project work. On a $12,880 balance, 1.5% is $193.20 per month.
• Flat fee: simpler on small invoices, where 1.5% of $400 is $6 and not worth the line. A $25 flat fee is common for service work; keep it proportionate, a $50 fee on a $300 invoice reads as a penalty and may be challenged.
• Either way, apply it monthly, not daily, and show the fee as its own line on the invoice with the date it was applied.

Grace period and timing

A short grace period, 5 to 7 days after the due date, costs you nothing and removes the “the check was in the mail” argument. Apply the first fee on the day the grace period ends, then on the same day each month while the balance is open. Your reminder schedule should mention the fee exactly once before it applies, for example in the 7-day reminder: “per our agreement a late fee applies after day 14”.

When to waive it

Waive the fee when the customer pays the principal promptly after the first notice, when the delay was your fault (a wrong amount, a lost invoice), and for good customers who are late once. Waiving is a tool: “I will remove the $193 fee if the balance is paid by Friday” converts better than the fee itself. Never waive silently; send a corrected invoice so the record matches.

Late fees and lien rights

A late fee is separate from your lien rights. In most states a mechanics lien secures the contract price for labor and materials; whether it also secures contractual interest and fees varies, and lien deadlines run from the last day of work regardless of any fee. If an invoice is heading past 30 days, check your state’s preliminary-notice and lien deadlines before the fee math; the fee is leverage, the lien is security.

Wording you can copy

On the estimate and invoice: “Payment is due on the date shown. Balances unpaid 7 days after the due date accrue a late fee of 1.5% per month (18% per year) or the maximum permitted by law, whichever is less, until paid. Fees are shown as a separate line on the invoice.”

In the 7-day reminder: “Per our agreement, a late fee of 1.5% per month applies to balances unpaid 14 days after the due date. Pay from the link below to avoid it.”