A formal notice of default is an official notification informing another party that they have failed to meet their obligations. You describe the outstanding payment or breach, request that they fulfil their obligations or make payment, and give them a clear deadline to do so.
The difference between a reminder and a formal notice of default is not the tone, but the purpose. A reminder is part of your payment follow-up. A formal notice of default serves as evidence: it records that you have given the other party one final, specific opportunity to fulfil their obligations.
If nothing happens afterwards, you are in a stronger position to take further action or exercise additional rights under your contract and the applicable law.
For B2B invoices in Belgium, your general terms and conditions, the agreement itself and the legislation on late payments in commercial transactions also play a role.
Payment reminder, demand for payment or formal notice of default?
In practice, you rarely take just one step. Most cases follow a similar sequence, with each stage serving a different purpose.
| Step | Purpose | When should you use it? |
|---|---|---|
| Payment reminder | Remind the customer that an invoice is overdue | Shortly after the due date, while maintaining the customer relationship |
| Demand for payment | Increase pressure and set a new deadline | When the reminder has been ignored |
| Formal notice of default | Formally notify the debtor of their default and set a final deadline | When amicable follow-up is unsuccessful and you want legal clarity |
| Legal debt recovery | Enforce payment | Once the deadline has passed. If the invoice is undisputed, recovery may be possible through IOS. If it is disputed, you must go to court. |
A payment reminder, demand for payment or formal notice of default can be useful in practice to increase pressure and clearly document your case. However, a prior formal notice of default is not a mandatory step for the IOS procedure.
When should you send a formal notice of default?
As soon as it becomes clear that the other party is not fulfilling their obligations and ordinary follow-up is no longer sufficient. Typical situations include:
- Your customer has not paid your invoice despite several reminders.
- A supplier fails to deliver within the agreed timeframe.
- Completed work contains defects that have not been corrected.
- An agreed service has not been provided, even though the deadline has passed.
In each of these situations, a formal notice of default gives the other party one final, clear opportunity to fulfil their obligations, while also documenting that this opportunity was given.
Is a formal notice of default always mandatory?
No. A formal notice of default is not mandatory in every situation, and certainly not when starting an IOS procedure.
For outstanding B2B invoices, a formal notice of default can be useful to clarify your position, increase pressure and document your case more thoroughly. However, it is not a legal requirement for taking further action through IOS.
An additional reminder beforehand is generally not mandatory either. In practice, many businesses still choose to send one because a short reminder or demand for payment by email is often enough to achieve results.
What should a formal notice of default contain?
A good formal notice of default is clear, factual and specific. No vague threats or emotional language. The aim is not to impress, but to provide legal and practical clarity.
Include at least the following:
- The full details of both parties.
- A clear reference to the agreement, invoice or order.
- A specific description of the breach or outstanding debt.
- The amount or performance you are still demanding.
- A reasonable deadline for the other party to fulfil their obligations.
- An explicit statement that this is a formal notice of default.
- What action you will take if no response or payment follows.
- The date, name and signature, or clear identification of the sender.
That last point is often overlooked, but it is precisely where the pressure lies. "Further action" says very little. "Legal debt recovery through a bailiff" makes the consequences clear.
If you would like to use a template, you can download our example of a formal notice of default and complete it as needed:
Free formal notice of default template
What is a reasonable deadline?
That depends on what you are requesting. For a standard outstanding B2B invoice, a short, specific deadline is often used in practice, for example eight calendar days. If the matter involves repairs, replacement or a more complex obligation, a longer deadline is more appropriate.
What matters is that your deadline is realistic and appropriate for what you are requesting. An unreasonably short deadline can work against you if the matter is reviewed later.
Should you send it by email or registered post?
In practice, sending a formal notice of default or reminder by email is perfectly acceptable. What matters most is that you clearly communicate what remains outstanding, what you are requesting and by when.
Registered post is an option, but it is certainly not always necessary. You often want to avoid making the process unnecessarily complicated. In many cases, a clear reminder or formal notice of default by email is sufficient.
However, check your contract and general terms and conditions. They may specify how formal notifications must be sent. If so, it is best to follow those requirements.
Example of a formal notice of default
Here is what a short formal notice of default for an outstanding invoice could look like:
Subject: Formal notice of default, invoice [invoice number]
[Company name] hereby formally places [debtor's name] in default for non-payment of invoice [invoice number], amounting to [amount], which was due on [date].
Despite previous reminders sent on [dates], payment has not been received.
We request that you pay the full outstanding amount within [number] calendar days of receiving this letter, to account [bank account number], quoting reference [reference].
If payment is not received, we reserve the right to take further action and, where applicable, claim interest and costs and initiate legal debt recovery in accordance with the agreement and applicable legislation.
[Date, name, position, signature]
Use this as a starting point, not as a template to copy without making changes. Always adapt the facts, amounts, deadlines and contractual references to your own case.
Your customer does not respond. What now?
If the deadline passes without payment or a response, follow this checklist:
- Keep the formal notice of default and proof of sending. These documents now form part of your case.
- Check whether the deadline has actually passed. Calculate from the date of receipt, not the date of sending.
- Calculate the current outstanding balance, including any interest and costs under the contract and applicable law.
- Check whether your customer has disputed the invoice in any way. This determines which recovery procedure you can use.
- Decide whether amicable follow-up is still worthwhile or whether it is time to proceed with legal debt recovery.
For larger amounts, approaching limitation periods, signs of solvency problems or a dispute, it is better not to wait too long. Every month of inactivity reduces your chances of getting paid.
What Unpaid does for undisputed B2B invoices
For undisputed B2B invoices in Belgium, Unpaid is the logical next step when payment reminders and a formal notice of default have not produced results.
Unpaid is not a traditional debt collection agency, but a digital platform for the legal recovery of outstanding B2B invoices through the IOS procedure (Recovery of Undisputed Debts), without having to go through a lawyer or the courts yourself.
How it works
Within five working days of submitting your case, a bailiff appointed by us visits your customer to formally notify them that the case has entered the IOS procedure.
From that moment, a period of 38 days begins during which your customer can pay or request a payment plan. If neither happens, an enforceable title is subsequently obtained, allowing assets to be seized. It is therefore a legally enforceable procedure that your customer cannot simply ignore.
What it costs
The basic principle is that your customer bears all the costs. When payment is made, you receive 100% of the claimed amount, and you can also recover 21% of the contractual compensation through VAT.
To start a case, you pay an advance to cover the bailiff's costs. This is refunded in full once your customer pays. The amount depends on your claim and follows the statutory bailiff fees. You can find an overview in our FAQ under "How much does Unpaid cost?".
There is also no subscription, no minimum invoice amount and no exclusivity agreement.
When it is not suitable
The IOS procedure only applies to undisputed debts between businesses. If your customer disputes the substance of the invoice, whether the amount, the goods or services provided, or the terms, the case is no longer undisputed and a different approach is required. Different rules also apply to consumer debts.
Not sure whether your invoice qualifies? The Invoice Check gives you an initial indication in just a few minutes. This is an assessment, not a guarantee.
Has your customer ignored previous demands for payment, and are they still not responding? Then it is time to start the Unpaid procedure.
Frequently asked questions
Can I send a formal notice of default myself without a lawyer?
Yes. In many cases, you can prepare and send a formal notice of default yourself, provided the letter is clear, complete and you can prove that it was sent. For complex contracts or large amounts, however, it is advisable to have it reviewed.
Is a formal notice of default sent by email legally valid?
Yes. A formal notice of default sent by email is generally legally valid. You do not always need to send it by registered post. However, make sure you can prove what you sent and when. Also check your contract and general terms and conditions, as they may contain specific formal requirements.
What if my customer disputes the invoice?
In that case, you are no longer dealing with a straightforward recovery of an undisputed debt. You must first resolve the underlying disagreement about delivery, quality, price or contractual terms.
For Unpaid, the fact that the debt is an undisputed B2B claim is a fundamental requirement. Read more about what you can do if your debtor disputes the invoice.
Can I immediately charge interest and additional costs?
That depends on your contract, general terms and conditions and the applicable law. For commercial transactions between businesses, you may be entitled to charge interest and certain additional costs, but these must be calculated correctly.
Does a formal notice of default interrupt the limitation period?
Not automatically. An ordinary formal notice of default does not interrupt the limitation period. Under specific legal conditions, a formal notice of default sent by registered post by a lawyer or bailiff can interrupt the limitation period.
Therefore, do not wait until the last moment if your invoice has been outstanding for a long time or if you are unsure which limitation period applies.
When should I seek professional help?
Do you have an undisputed B2B invoice that remains unpaid after its due date? You can initiate an IOS procedure through Unpaid. A prior payment reminder or formal notice of default is not required.
The sooner you take action, the sooner you can start recovering your outstanding payment.
