Is your customer slow to pay an invoice? A good reminder letter may be all it takes to break the deadlock without damaging the business relationship. But how do you structure a powerful, polished and effective message? In this article, find out how to write a clear, well-argued and respectful customer reminder letter, following the best practices of credit management. We’ll also look at how dunning software like Aston Cash Collection can help you automate this process with precision.
To learn more, read our guide: Customer Follow-Up and Collection: Best Practices.
Table of contents
Why a well-written dunning letter makes all the difference
- It formalizes your collection approach while maintaining a courteous tone.
- It clarifies the situation for the customer (amount, due date, conditions).
- It can avoid a dispute by initiating a constructive discussion.
- It shows your professionalism and reinforces your credibility.
- It constitutes useful written proof in the event of a dispute.
The 7 essential elements of a good dunning letter
Here is a summary of the key elements to include in each letter:
1. Invoice reference
2. Exact amount due
3. Past due date
4. Clear subject (Reminder for unpaid invoice)
5. Polite but firm
6. Contact details for easy response
7. Mention of penalties (if provided for in your GCS)
🧠 Even the best letters lose their effectiveness if they’re not sent at the right time, to the right person, with the right message.
That’s exactly what Aston AI enables: automated, personalized, always professional reminders.
Simple example of a customer reminder letter - Level 1 reminder
Subject: Reminder for unpaid invoice
Dear Sir/Madam,
Unless there is an error or omission on our part, invoice no. [XXX], in the amount of € [XXX], due on [date]has not yet been paid.
We would be grateful if you could arrange payment as soon as possible.
Should you require any further information, please do not hesitate to contact us.
[Name / Company / Contact]
When should you send your dunning letters? The right timing
- Preventive reminder: 3 to 5 days before the due date.
- Amicable reminder (level 1): D+5.
- Insistent follow-up (level 2): between D+10 and D+15.
- Pre-contentious reminder: after D+30 (with or without formal notice).
Tip: Aston AI's automated clips
Reminder software such as Aston Cash Collection enables you to automate your letters while at the same time personalizing them with precision. Thanks to dynamic clips, each message automatically integrates the following data:
- Customer name
- Invoice reference and amount
- Expiry date
- Specific terms of payment
- Contact details for your accounting department
The result: considerable time savings and consistently professional, accurate communication.
With Aston Cash Collection, AI doesn’t just simplify your dunning: it anticipates delays, prioritizes your needs and gives you a clear view of your cash flow.
👉 Find out how artificial intelligence is revolutionizing customer collections in this article.
Real-life case: effective relaunching without damaging the customer relationship
A B2B consulting firm was using a home-made spreadsheet to keep track of its unpaid invoices. The result: oversights, duplicates and poor customer relations. With Aston AI, they industrialized their reminders:
- 70% of settlements obtained after the first reminder.
- Tone adapted to the customer’s profile.
- DSO reduced by 15 days in 4 months.
- Easing commercial tensions through a rigorous yet professional approach.
Comparison: manual or automated relaunch?
Here is a table comparing the two approaches:
Manual restart : | Automated relaunch (with Aston Cash Collection from Aston AI): |
+ Suitable for sensitive cases | + Fast, reliable, traceable |
Time-consuming and difficult to trace | + Customized with dynamic clips |
Risk of errors and omissions | + Integrated into DSO / WCR indicators |
Requires initial configuration |
Common mistakes to avoid
- Waiting too long to relaunch
- Use a tone that is either too aggressive or, on the contrary, too passive
- Omit key information: reference, deadline, amount
- Don’t include a quick contact option (phone, email)
- Don’t follow up regularly: a single reminder is rarely enough.
- Follow-up all customers in the same way, without segmentation
Mini-story: what happens when you don't raise?
In an industrial SME, a long-standing customer failed to pay two invoices for €8,000. No one reminded him, thinking that he would pay “as usual”. Three months later, the company filed for bankruptcy. The claim was lost. A simple reminder on D+5 could have changed everything. Dunning is not an aggression: it’s life insurance for your cash flow.
FAQ - Frequently asked questions
Q: Do I have to call back even a good customer?
A: Yes, preventively and courteously. It shows you’re thorough.
Q : Can I send a reminder by SMS or telephone?
A: Yes, but a paper trail is essential.
Q: What’s the difference between a reminder letter and a formal notice?
A: The dunning letter is amicable. A formal notice is legally binding on the debtor.
Q: When should I outsource collection?
A: From D+45 or if no action is taken despite several reminders.
Mastering the art of customer reminder means securing your cash and professionalizing your image. A well-written letter sent at the right time can make all the difference. And with reminder software like Aston AI, you can take your reminders to the next level: automatic, personalized, traceable and effective. Don’t let an unpaid invoice jeopardize your business.
See also: Customer follow-up via text message.
