How to Write a Demand Letter for an Unpaid Contractor Invoice

This guide explains when to send one, what to put in it and what to do afterward. It is general information, not legal advice.

When a demand letter makes sense

Send one when:

• You have sent at least two or three polite reminders with no payment.
• The client has stopped responding or has missed a promised payment date.
• You have ruled out a simple problem, like an invoice that went to spam or a wrong amount.

Hold off if the client has raised a specific, reasonable complaint about the work. Address that first. A demand letter on a genuinely disputed invoice usually hardens positions.

Check your lien deadline first

If the work was on real property, find your state’s mechanics lien deadline before you write anything. Lien deadlines usually run from your last day of work, not your invoice date, and some states require a preliminary notice early in the job. A demand letter does not pause those clocks. Your state legislature’s website has the statute, and many state contractor licensing boards publish plain-English summaries. For example, see California Civil Code 8412 or Florida Statutes 713.08.

Some states require a demand before you sue

In some courts, a written demand is a required or expected step before filing a small claims case. The California Courts self-help center, for example, says you must ask the defendant for payment before filing in small claims (selfhelp.courts.ca.gov). Check your own state court’s small claims page. Your letter doubles as proof that you asked.

What to include

Keep it to one page. Include:

1. Your business name, license number (if any) and contact details.
2. The client’s name and the job address.
3. What you did and when. One or two sentences. “Replaced the main electrical panel on August 4, 2026, per signed estimate #221.”
4. The amount owed. Invoice number, original amount, payments received, balance due. Add late fees only if your contract allows them.
5. Your prior attempts. Dates of reminders and calls.
6. A specific deadline. Use an exact date, usually 10 to 14 days out. “Payment must be received by October 24, 2026.”
7. How to pay. A payment link, mailing address or both. Make paying easier than ignoring.
8. What happens next. State the one or two steps you will actually take, such as recording a mechanics lien or filing in small claims court. Do not threaten things you will not do, and never threaten criminal charges or contacting the client’s employer.
9. An open door. Invite them to call if they believe something is wrong with the invoice.

How to send it

• Send by certified mail, return receipt requested, so you can prove delivery.
• Email a copy the same day so there is a timestamp and an easy way to reply.
• Keep copies of everything: the letter, the receipt, and any replies.

Sample demand letter

Rivera Electric LLC, License #000000
55 Oak Road, Springfield
(555) 010-2020 | billing@example.com

October 10, 2026

Pat Lee
18 Elm Street, Springfield

Re: Unpaid Invoice #221, panel replacement at 18 Elm Street

Dear Pat,

On August 4, 2026, we replaced the main electrical panel at 18 Elm Street under signed estimate #221. The work passed inspection on August 6. Invoice #221 for $3,850 was due on August 20, 2026. We have received no payment.

We sent reminders on August 22, September 3 and September 17, and called on September 24.

Please pay the balance of $3,850 by October 24, 2026. You can pay online at [payment link] or mail a check to the address above.

If payment is not received by that date, we plan to file a claim in small claims court for the balance and filing costs.

If you believe something about the work or the invoice is wrong, please call me at (555) 010-2020 before that date so we can talk.

Sincerely,
Alex Rivera, Owner

After you send it

• They pay. Send a thank-you and a receipt. If you recorded a lien, release it promptly.
• They want a payment plan. Put it in writing with dates and amounts, and keep an eye on lien deadlines, which do not move just because they promised.
• They dispute the work. Ask for specifics in writing. Decide whether a fix or a partial credit is fair.
• They ignore it. Follow through on exactly what you said, on the date you said.

Prevent the next one

Most demand letters are avoidable. Clear payment terms in the contract, a deposit, and steady, polite reminders starting the day an invoice is due recover most balances long before this point.

That last part is what Still Due is built for. It emails your clients polite reminders on a schedule with a Stripe Pay button, and payments go to your own Stripe account. It does not send demand letters for you, but it makes it a lot less likely you will need one.

See also the electrician overdue invoice email and the final reminder.

General information only, not legal advice. Rules for liens, small claims and collections vary by state.