Can You Charge a Late Fee on a Contractor Invoice?
Yes — but only if the terms were in writing before the work started. Here is what makes a late payment fee legally defensible, how much to charge, and exactly what to put on your invoices and contracts.
Yes. Contractors can charge a late payment fee on overdue invoices. But slapping a fee onto an invoice after the fact and expecting a client to pay it is a different matter entirely. According to AllLaw, you must have a written agreement in place that outlines your late payment policies, and your fees need to stay within the limits set by your state's laws. No written agreement, no enforceable fee.
This article covers what makes a late payment fee legally defensible, how much to charge, and exactly what to write on your invoices and contracts so the fee holds up if a client pushes back.
The Written Agreement Requirement
A late payment fee is only enforceable when two conditions are met: the client agreed to it in advance, and the terms were in writing.
According to AllLaw, when a client misses a due date, you as the business owner become a de facto creditor. You are extending credit and giving them more time to pay. As with any credit transaction, you must spell out the terms in advance and in writing to legally impose the charge. Both you and the client should sign the agreement.
This means you cannot decide to add a late payment fee after a client is already overdue on an invoice that never mentioned one. According to Hiveage, you cannot retroactively decide to add a fee after a payment is already late. The language you use forms the legal basis for your right to collect.
Where does this written agreement live? In two places:
- Your contract or service agreement. This is the primary legal document. It should state the payment terms (e.g., Net 30), the late fee amount or percentage, and when the fee kicks in.
- Your invoice. Restate the late fee terms on every invoice you send. The contract is the legally binding document, but the invoice serves as a reminder and keeps the terms visible.
How Much to Charge
Under the law, a late payment fee cannot be used to penalize a client or collect extra revenue. According to AllLaw, you can charge only an amount that covers the costs and losses you incurred as a direct result of the late payment, such as the interest you would have earned had the money been deposited on time, and the time and supplies required to follow up.
In practice, most contractors land on one of two structures:
Percentage-based fees. The standard range is 1% to 1.5% of the invoice amount per month, according to both AllLaw and FreshBooks. At 1.5% monthly, that works out to 18% annually. QuickBooks puts the typical range at 1% to 2% monthly.
Flat fees. Business.com notes that flat fees typically run $25 to $50, charged when payment becomes overdue. A flat fee works well when you know the invoice amount at contract signing, because you can confirm it falls within state limits. But if you bill hourly and the final total is unknown, a percentage-based fee is easier to keep compliant.
You can also combine both. According to PaidNice, a combined policy is common: a fixed fee once an invoice is overdue, then interest on the outstanding balance. Spell out clearly when each part applies.
AllLaw suggests that limiting your fees to a maximum of 10% per year should generally keep you from running afoul of state laws across the board.
State Limits You Need to Check
Late fee limits vary by state, and ignoring them can make your entire fee clause unenforceable. Most states regulate this through usury laws, which cap the interest rates you can charge.
According to PaidNice's 2026 state-by-state guide, more than 30 US states have no statutory maximum late fee for B2B invoices. But several states do impose specific caps and grace period requirements. Before setting your rate, look up the rules for your state. If you operate across state lines, the client's state may apply.
If your client challenges a fee in court and the court finds it excessive, AllLaw warns that you can end up paying more in penalties than the fee you originally charged. Keeping rates reasonable protects you even in states with no explicit cap, because courts in every state can void fees they consider punitive rather than compensatory.
What to Write on the Invoice
Your invoice needs four things related to late fees, according to AllLaw:
- The date of the invoice
- The balance owed
- The payment terms (e.g., "Net 30 days")
- A statement of the late fee that will apply
FreshBooks recommends keeping it simple and brief. Their example: "Payment is due within 30 days. Please be aware that we will charge 1.5% interest per month on late invoices."
Here are three templates you can adapt, depending on your fee structure:
Percentage-Based
Payment due within 30 days of invoice date. Invoices not paid within 30 days will incur a late payment fee of 1.5% per month on the outstanding balance.
Flat Fee
Payment due within 30 days of invoice date. A $50 late payment fee will be applied to any invoice not paid by the due date.
Combined (Flat Fee + Interest)
Payment due within 30 days of invoice date. A $25 administrative fee applies to overdue invoices. Additionally, a 1.5% monthly interest charge will accrue on the unpaid balance beginning 30 days after the due date.
Whichever template you use, the same language should appear in your contract. The invoice restates it; the contract establishes it.
Put It in the Contract, Not Just the Invoice
An invoice is a request for payment. A contract is a legally binding agreement. If a client disputes your late payment fee, the contract is what matters.
According to FreshBooks, because a contract is legally binding, it is important to clearly state your late fee terms within the contract. Including your late fee terms in your contracts also ensures clients know the policy before any work begins.
Here is a sample contract clause adapted from Hiveage's templates:
Late Payment. If payment is not received by the due date stated on each invoice, Client agrees to pay a late payment fee of 1.5% per month (18% per annum) on the outstanding balance. This fee will begin accruing the day after the due date. If the invoice remains unpaid after 60 calendar days, [Your Company Name] reserves the right to suspend work until the balance, including all accrued late fees, is paid in full.
Notice that this clause includes the rate, when it starts, and the consequence of continued nonpayment. All three elements matter.
When to Bring Up the Policy
Timing matters as much as wording. The worst moment to introduce a late payment fee is after a client has already missed a deadline. At that point, it feels punitive and you have no legal standing to enforce it.
Bring it up during the contract negotiation, before any work starts. FreshBooks recommends giving clients a heads-up about your billing policy. You can do this by email, phone, or in person, but have the discussion with each client and allow them to ask questions so they are not caught off guard.
For existing clients who never signed a late fee clause, you have two options:
- Amend the contract. Send a contract addendum that includes your new late payment policy, and have the client sign it before it takes effect.
- Apply it to new projects only. The next time you sign a scope of work or project agreement, include the clause. This avoids any retroactive enforcement issues.
Late Fees vs. Payment Reminders
A late payment fee is a financial incentive. A payment reminder is a communication tool. They work together, but they are not interchangeable.
The fee gives clients a reason to prioritize your invoice. The reminder makes sure they do not forget it. Hiveage notes that 55% of all B2B invoices in the US were paid late in 2023. Many of those late payments were not deliberate. The client's AP person was busy, the email got buried, or the invoice sat in a queue behind others.
A well-timed reminder sequence catches those cases before a late fee ever needs to apply. Send a reminder a few days before the due date, another on the due date, and escalate if the invoice goes past due. For a complete breakdown of how to time reminders and which channels convert best, see our invoice payment reminders guide. The late payment fee is your backstop for clients who still do not pay after repeated follow-up.
If you have a late payment policy in place, your reminders should reference it. Something like: "Per our agreement, a 1.5% monthly late fee applies to invoices not paid within 30 days." That connects the reminder to the contractual obligation without being aggressive.
What Happens If a Client Refuses to Pay the Fee
If your late fee clause was in the signed contract and the amount is within state limits, the client is legally obligated to pay. That does not mean they will.
Your escalation path typically looks like this:
- Send a revised invoice with the late fee itemized as a separate line. Make it visible.
- Follow up in writing. Reference the contract clause and the specific section that covers late fees. Keep the tone professional.
- Send a formal demand letter. This is a written notice that you intend to pursue collection if payment (including the late fee) is not received by a specific date.
- File in small claims court or hand off to collections. Courts routinely enforce reasonable late fee clauses that were agreed to in writing. AllLaw notes that you can include the late fees in a collections action or small claims filing.
Most clients pay before step 3. The demand letter signals that you take your payment terms seriously and have the documentation to back them up.
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