Demand Letter Generator for Unpaid Invoices

Not legal advice. For significant or disputed amounts, have a licensed attorney review before sending.

1. The parties

2. The invoice

3. The interest

The rate stated in your contract or on the invoice.

4. The demand

About this page

This page assembles a letter from your inputs and public statutes; it is general information.

Before you send: read every line — you are responsible for the letter's contents. Verify the cited statute against the official source in the state table, and keep a copy of the letter, the invoice, and your delivery evidence together. Not legal advice.

How the interest is computed

Simple interest: interest = amount × (APR ÷ 365) × days overdue

Days overdue are counted from the invoice due date to today. The same formula (and the same verified state table) powers our late fee calculator — start there if you only need the number, come here when you need the letter.

Where the statutory rates come from

When you pick “use my state's statutory default”, the rate, the statute citation, and (optionally) the verbatim statutory text come from our 51-jurisdiction reference table — every row individually verified against the primary source with the verification date shown, and re-checked on a published schedule (changelog). States that set the rate by formula or periodic order link the official current-rate page instead of a frozen number.

Demand letter or final-demand invoice?

Short answer: send a demand letter when you need one formal document that sets out the debt, the interest and its basis, and a payment deadline. Re-send the invoice itself, marked as a final demand, when the client only needs the same invoice again to pay against. You can also do both: send the letter with the invoice attached.

When a demand letter fits

  • Your reminders have gone unanswered and you want a dated, formal record of the demand.
  • You are claiming interest and want the rate and its basis (your contract, or your state's statute) stated in writing.
  • You want to set a deadline and say what happens if it passes.

When re-sending the invoice fits

  • The client has not disputed the invoice, and their accounts team pays against invoice documents.
  • You want the amount due, the original invoice number and the due date on one page they can process as it is.

How to re-send the invoice as a final demand

  1. Choose the generator. The PDF from the free invoice generator on our home page always prints the heading "INVOICE". To print your own heading, use a generator whose template prints the Document Title field, such as the freelance invoice generator.
  2. Load or re-enter the original. Each generator keeps your last draft in this browser, so if you made the original invoice in that generator on this device, it reloads when you open the page. Otherwise, re-enter the original invoice.
  3. Keep what identifies the debt: the original invoice number, invoice date, line items and due date, so the document reads as the same invoice, not a new charge.
  4. Replace the editor's sample content. A new draft opens with sample values: replace the placeholder business and client details, payment details, line items, notes and terms, and set the tax label and rate to what the original invoice showed (rate 0 if it charged none). In the freelance generator, also set Deposit Paid to what the client has actually paid (0 if nothing).
  5. Change the Document Title (up to 100 characters) to, for example, "FINAL DEMAND — INVOICE". Leave Document Type on Invoice, because choosing a type rewrites the title. On the home page generator, where the heading stays "INVOICE", put the final-demand wording and the new deadline in the Notes field instead.
  6. Add interest only if you are entitled to it. If your contract or your state's rule allows it, add the interest computed on this page as its own line item, for example "Late-payment interest: [rate]% a year, simple, [days] days from [due date]", quantity 1. A percentage tax rate and any discount set in the editor apply to every line, including this one, so check the tax and the total before you download. The state table in the late fee calculator links a page for each state with its statute.

For the covering email, adapt the "Final Notice" script in our invoice payment terms guide.