You sent the invoice 45 days ago. The client finally responds saying they will pay next week. You want to add a late fee, but you are not sure if you can, what amount is fair, or whether you can actually collect it. Late fees work, but only if you set them up correctly before the invoice goes out.
Can You Even Charge a Late Fee?
You can charge a late fee if your contract or invoice clearly states it before the work is done. You cannot invent a late fee after the invoice is already overdue and expect it to stick.
Most states allow late fees as long as the rate is reasonable and disclosed in advance. A few states cap the maximum interest rate you can charge on consumer debts. If you are working for a homeowner, keep the rate moderate to avoid running into usury limits.
If your existing contract does not mention late fees, you can still ask for one, but the client can refuse and a court likely will not enforce it. Fix this going forward by updating your contract template today — and if the invoice is already unpaid with no fee on it, treat it as a straightforward unpaid-invoice problem instead.
How Much to Charge
There are two common ways to structure a late fee. Pick one and apply it consistently.
- Flat fee: a one-time charge like $50 or $75 added once the invoice passes the due date.
- Monthly interest: a percentage of the unpaid balance, typically 1% to 1.5% per month (12% to 18% annualized).
For most residential contractors, 1.5% per month is the standard. On a $4,000 invoice, that is $60 the first month, then $60 again the next month on the remaining balance. It is enough to get attention without looking predatory.
Check your state cap before you set the rate. Some states limit interest on unpaid consumer debts to 10% or 12% per year unless you have a signed agreement specifying otherwise.
Write It Into Your Contract and Invoice
The late fee clause needs to appear in two places: the original contract or work agreement, and the invoice itself. Both should use the same language and the same numbers.
Payment is due within 30 days of the invoice date. Invoices not paid by the due date are subject to a late fee of 1.5% per month (18% per year) on the unpaid balance, applied monthly until paid in full.
Put this in your contract under payment terms. Put it on every invoice in the footer or below the total. If the client signs the contract or pays earlier invoices without objecting, you have a much stronger case.
When to Apply the Fee
Do not slap on a late fee the day after the invoice is due. Send a polite reminder first. Most clients pay within a week of a nudge, and you keep the relationship intact.
A sensible schedule looks like this:
- Day 1 past due: friendly reminder email, no late fee yet.
- Day 10 past due: second reminder, mention the late fee that kicks in at day 15 or 30.
- Day 30 past due: apply the late fee, send an updated invoice showing the new total.
- Day 60 past due: apply the second month of interest, send a formal demand letter.
Always send the updated invoice with the late fee added as a separate line item. Do not bury it in the total. The client should see exactly what the fee is and why it was charged.
How to Actually Collect the Fee
Charging a late fee on paper is easy. Getting the client to pay it is the hard part. Clients will often pay the original invoice amount and ignore the fee, hoping you will let it slide.
If a client pays the base invoice but skips the late fee, apply the partial payment to the late fee first, then to the principal. Send a short email confirming you received the payment and noting the remaining late fee balance. Keep it factual.
If they refuse to pay the fee, you have a decision to make. For small amounts (under $100), it is often not worth the fight. For larger fees that have built up over months, treat the unpaid late fee as part of the overall debt and escalate it the same way you would any unpaid invoice.
Escalating When They Refuse to Pay
If the invoice and accumulated late fees go unpaid past 60 days, it is time for a formal demand letter. Include the original invoice amount, every late fee charge with dates, and the total owed. Reference the late fee clause in your contract.
Small claims courts will generally award reasonable late fees if you can show they were disclosed in advance and the rate is not excessive — see the small claims filing walkthrough for what to bring. Bring the signed contract, the invoice with the late fee terms, and a record of every reminder you sent.
Writing a clean demand letter that includes accrued late fees, references your contract terms, and points to your state's small claims limit is exactly what PaperHammer drafts. You fill in the invoice details, the fee schedule, and the dates. It produces three escalating versions you can send in sequence. $19, ready in about five minutes.