Writing a mise en demeure (formal notice) in France

A deposit that never comes back, an unpaid invoice, a builder who doesn't finish the job. In France, before going to court, there's almost always one step: the mise en demeure (formal notice). It's a letter that clearly asks the other side to do what they owe, within a set deadline. It's simple to write, and it often changes what happens next.

What a mise en demeure is for

It has two effects. The first is practical: many disputes stop there, because the other person understands you'll go further. The second is legal: the French Civil Code (Code civil) attaches consequences to it.

• The debtor is put on notice “by a summons or by an act containing a sufficient demand” (article 1344). A clear letter is enough.
• For a sum of money, late-payment interest at the legal rate runs from the formal notice (article 1344-1).
• Unless the failure to perform is final, you can only claim damages after giving the debtor formal notice to perform within a reasonable time (article 1231).

And in front of a judge, showing that you first tried to settle things amicably counts.

What it must contain

1. Your name and address, and the recipient's.
2. The place and date.
3. The words “mise en demeure” in the subject line. The letter has to stand apart from an ordinary reminder.
4. The facts, briefly: the contract, the date, the sum or the service at issue.
5. Exactly what you're asking for: pay a given sum, return a given item, finish given work.
6. A deadline: often eight or fifteen days. It has to be reasonable.
7. What you'll do if nothing happens: refer the matter to a conciliateur de justice (a free court-appointed mediator) or to the court.
8. Your signature.

Stay factual and polite. The letter may end up in front of a judge. Write it in French when the recipient is in France: it's what they, and a French judge, will read.

A sample: the rental deposit

After a tenant moves out, the landlord must return the deposit (dépôt de garantie) within one month if the move-out inspection report (état des lieux de sortie) matches the move-in one, or two months otherwise (article 22 of the law of 6 July 1989). After that, the amount owed is increased by 10% of the monthly rent excluding charges for each month of delay begun. Here's a letter to adapt, with fictitious people and amounts. It stays in French, since it goes to a French recipient; an English gloss follows.

In English, the letter says:

• Header: sent by registered letter with proof of delivery; subject: formal notice to return the deposit.
• Facts: I rented the flat at 5 rue Garibaldi until 31 July 2026; the move-out report matches the move-in report; I handed back the keys that day.
• The breach: the €800 deposit hasn't been returned, although the one-month deadline in article 22 of the law of 6 July 1989 has passed.
• The demand: I formally require you to pay me, within fifteen days of receiving this letter, €800 plus 10% of the monthly rent excluding charges for each month of delay begun, as that same article provides.
• What comes next: without payment by then, I'll refer the matter to the conciliateur de justice, then, if needed, to the competent court.
• Closing: the standard French formal sign-off (“Yours faithfully”), then the sender's name.

How to send it

The law doesn't always require a specific form. But you'll have to prove the letter left, and when it was received: the date of receipt is what starts the deadline you give. The usual way is the lettre recommandée avec accusé de réception (registered letter with proof of delivery). An email is easier to dispute, and an ordinary letter leaves no trace.

If the recipient doesn't collect the letter, read unclaimed registered letter. When a lot is at stake, a commissaire de justice (French court officer) can also serve a formal demand (sommation), which carries more weight but costs more.

Writing and sending it with an AI assistant

A mise en demeure is a good job for an AI assistant: you tell it what happened, with the dates and amounts, and it turns that into a clear letter in French, with the right articles. With Cachet connected, it can also send it: it checks the address, shows you the exact preview and the price, then gives you a payment link. The letter goes by registered letter with proof of delivery, from €9.99, and the assistant tracks its delivery. Always check the facts and amounts before approving: the letter goes out in your name.

The step-by-step is in send a letter with ChatGPT or Claude.

Frequently asked questions