What is a registered letter?
A registered letter is a letter sent via the postal service or an electronic registered service, where you receive proof of both posting and delivery.
It provides you with evidence of dispatch and receipt, which is useful if a customer later claims not to have received the invoice or formal notice.
In what form can a registered letter be sent?
In Belgium, you can send a registered letter in two ways:
- Physically by post, where you receive a paper receipt.
- Electronically registered, via authorised platforms (e.g., DIGICONNECT or Aangetekend), with digital proof of posting and delivery.
Both forms have the same legal standing and can be used as evidence in court proceedings.
Is a registered letter mandatory?
The short answer: no, sending a registered letter is not legally required to collect an unpaid B2B invoice in Belgium.
Once the invoice is overdue, your customer is in default, and you may take further (legal) action.
However, a registered formal notice is sometimes recommended:
- It demonstrates that you have formally requested payment from the customer.
- It strengthens your evidence in case of disputes or legal proceedings.
But remember: you do not have to send this formal notice by registered post. You may also send it as a document by email to your customer.
Step-by-step plan for collecting unpaid invoices
Following up on unpaid invoices is best done in a structured way. Follow the plan below to maximise your chances of payment and protect your cash flow.
1️⃣ Informal reminder
Send a friendly payment reminder by email or phone shortly after the due date. Sometimes a forgotten payment is quickly resolved with a simple prompt.
2️⃣ More formal reminder
If payment is still outstanding, send a more formal reminder by email or post clearly stating the invoice number, the amount due, and a new, short payment deadline.
3️⃣ Formal notice of default
Still no response? Send a formal notice of default, registered or not, formally demanding payment within a specific period (e.g., 8 days). Also state that you will take further (legal) action if payment is not made.
Download formal notice template
4️⃣ Legal recovery via Unpaid
No payment and no dispute? You can then easily recover your unpaid B2B invoice legally through Unpaid using the RUD procedure (Recovery of Undisputed Debts).
This expedited procedure has many benefits:
- Speed: faster than a traditional legal process through the courts
- Cost-efficient: no solicitor or court fees
- Simple: submission takes only a few minutes and is entirely online
5️⃣ Dispute? Then through the courts
If the invoice is disputed, the IOS procedure is not available. No matter how trivial the dispute may seem, only a judge can decide. You will therefore need to pursue your claim through the courts (with or without a solicitor).
A registered letter is not mandatory, but wise
Although a registered letter is not compulsory to recover a B2B invoice in Belgium, it is an important tool in your debt management to strengthen your evidence and apply pressure on your client.
If payment remains outstanding, don’t wait until your cash flow suffers due to late payers. Unpaid helps you recover your money quickly via the RUD procedure.