Why an invoice gets forgotten
An invoice sent by email is quickly buried in an inbox. With a business customer, it sometimes waits for an accounts department that processes payments in batches once a week. With a private customer, it is simply put off until later, with no bad intent. In both cases, silence means nothing in particular: it is up to you to follow up, at a pace that rises gradually from a polite reminder to a formal notice.
The three follow-up stages
An effective follow-up runs to a clear rhythm: a reminder email around D+8 after the due date, a more direct SMS around D+20, then a formal notice letter from D+30 if nothing has moved. Each stage changes tone and channel, but never politeness: a customer who feels accused pays more slowly than a customer who simply feels reminded.
This rhythm assumes you know, for each invoice, which stage it has reached. With a handful of cases, a table is enough. Past a dozen open invoices, most tradespeople and shopkeepers lose track: one follow-up goes out twice, another never goes out at all. It is this gap between the planned pace and the real pace that lets an unpaid invoice drag on well beyond 30 days.
Stage 1, D+8: the reminder email
“Hello, I wanted to let you know that invoice no. [number] of [date], for [amount], does not seem to have been paid yet. It may simply have been overlooked: do tell me if you need it sent again or need more time. Have a good day, [first name].” This first message stays light. It assumes good faith and offers an easy way out.
Stage 2, D+20: the text that adds pressure
“Hello, invoice no. [number] for [amount] has been unpaid since [date]. Please settle it within 8 days or contact me to discuss it. [first name], [company].” An SMS is almost always read within the hour, unlike an email. It sets a firm deadline without being aggressive: you ask for a payment or a call, and the two options never stay open indefinitely.
Stage 3, D+30: the formal notice letter
“Dear Sir or Madam, despite our reminders of [dates], invoice no. [number] for the amount of [amount], due on [date], remains unpaid to date. We hereby give you formal notice to settle this sum within 15 days of receipt of this letter. Failing that, we reserve the right to begin the recovery proceedings provided for by law.” This letter is sent by recorded delivery with proof of receipt. It is the first document that counts legally if the matter ever has to go further.
The late payment penalties to mention
French law provides for late-payment penalties between businesses from the day after the due date, along with a fixed recovery-costs allowance. These terms should already appear in your terms of sale and on your invoices: repeat them in the formal notice letter, without inventing them or negotiating them case by case. For the exact rate applicable to your activity, your accountant or the tax authorities remain the source to consult.
With a private individual, these penalties between businesses do not apply in the same way: better to keep a firm but courteous tone, and save any mention of debt recovery for the case where the formal notice has no effect. In both cases, the point of the letter is not to intimidate, it is to leave a dated written record before considering a heavier step.
What you should never write
Avoid anything that sounds like a judgement on the person: “you never pay on time”, “this is unacceptable”. Stick to the facts: the invoice number, the amount, the due date. A factual follow-up also protects your position if the case ends up in court: aggressive or vague messages do more harm than good. Avoid promises you will not keep too, such as threatening legal action in the very first follow-up: keep that option for the formal notice letter, when it actually means something.
The version that runs itself
The real obstacle is not writing those three messages, it is remembering them for every invoice, at D+8 then D+20 then D+30, without ever missing one. That is what we automate for invoice follow-ups: each stage goes out at the right moment, in the right tone, and stops as soon as the payment arrives. To go further on the method and the timings, our article on how to follow up unpaid invoices sets out the full cadence.