Key takeaways
- The list of mandatory invoice details in Belgium is set out in Article 5 of Royal Decree no. 1, which transposes the EU VAT Directive.
- The core set covers the date, a unique sequential number, the identity and VAT number of the parties, the description of the goods or services, and the VAT breakdown per rate.
- Some transactions require specific wording, such as "Reverse charge" when the VAT is due by the customer.
- With Peppol e-invoicing these details do not disappear: they move into structured fields that compliant software checks before sending.
Why mandatory invoice details matter
An invoice is not just a receipt: it is the document that justifies a transaction and gives your customer the right to deduct VAT. That is why its content is framed by law rather than left to free drafting. In Belgium, the list of mandatory invoice details is set out in Article 5 of Royal Decree no. 1 of 29 December 1992, which transposes the EU VAT Directive (Directive 2006/112/EC).
The stakes are concrete. An incomplete invoice can be rejected by the authorities, deny the customer their deduction and trigger penalties. A compliant invoice, by contrast, is processed without friction, whether sent as a PDF or, increasingly, in a structured electronic format. This article details what must appear on a Belgian invoice, how to identify the parties correctly, and what the move to Peppol changes.
Royal Decree no. 1
lists the mandatory invoice details in Belgium
Directive 2006/112/EC
the harmonised baseline at EU level
issue deadline
by the 15th day of the month after the chargeable event
The mandatory invoice details in Belgium
The minimum content of an invoice is defined precisely. Most transactions fall under the same core set, listed below. An invoice that omits one of these items is incomplete for VAT purposes.
What a compliant invoice must show
The date of issue
The day the invoice is drawn up.
A unique sequential number
A continuous numbering that identifies the invoice with no duplicate or unexplained gap.
The supplier's identity and VAT number
Name or business name, address and VAT identification number of the issuer.
The customer's identity
Name and address; the customer's VAT number is required when the customer is itself a taxable person.
The date of supply or of the advance payment
The date of delivery or service, or of receipt of an advance payment, where it differs from the date of issue.
The description of the goods or services
Usual name and quantity, precise enough to identify the transaction.
The taxable amount per rate
The amount excluding VAT, broken down by applicable rate, plus any discounts not included in the unit price.
The VAT rate and amount
The rate applied and the total VAT due, expressed in euros.
Any specific wording
Any wording justifying an exemption, the reverse charge or a special scheme.
These details apply regardless of the medium. An invoice sent as a PDF, on paper or over the Peppol network must carry exactly the same information: it is the content that makes it compliant, not the format.
The VAT number and identifying the parties
Of all these details, identifying the parties correctly raises the most questions. The supplier's VAT number is always mandatory. The customer's is mandatory as soon as it acts as a taxable person: that covers almost all business-to-business relationships (B2B) and, without exception, intra-Community supplies, where the customer's valid VAT number determines the applicable regime.
In Belgium, the VAT number matches the enterprise number registered with the Crossroads Bank for Enterprises, prefixed with "BE". An error on this number is not trivial: it can be enough to have the deduction refused at the customer's end. Checking a partner's VAT number before invoicing is therefore a sound habit, all the more so as public validation tools exist.
Legal detail or good practice: do not confuse the two
Plenty of useful information appears on an invoice without being required by VAT law. Confusing it with the legal details leads either to thinking you are compliant when the essentials are missing, or to neglecting items that are commercially decisive. The table below sorts them out.
| Detail | Required by VAT | Strongly advised | |
|---|---|---|---|
| VAT number of the parties | |||
| Sequential number and date of issue | |||
| VAT rate and amount | |||
| Due date and payment terms | |||
| IBAN and structured reference | |||
| Customer's purchase order reference |
The due date illustrates the nuance well: it is not a VAT detail, but it is decisive for collection and for late-payment interest between businesses. Treating it as optional is a common mistake.
Special cases: reverse charge, exemption and advance payments
Some transactions change what the invoice must state. The most common is the reverse charge: when the VAT is due by the customer rather than the supplier, the invoice shows no VAT amount but carries the wording "Reverse charge". This mechanism applies notably to certain construction work between taxable persons and to intra-Community supplies of goods.
Exempt transactions follow the same logic: the invoice must cite the provision that justifies the absence of VAT. Finally, when an advance payment is invoiced before delivery, the date that advance is received becomes a detail in its own right as soon as it differs from the date of issue. Where a specific case is in doubt, the reference remains Article 5 of Royal Decree no. 1 and the guidance published by the FPS Finance.
Compliant invoices, without checking the details by hand
YouInv pre-fills the mandatory details, checks the VAT number and produces a compliant invoice, as a PDF or in the Peppol format.
Mandatory details and Peppol e-invoicing
The move to structured e-invoicing removes none of these details: it relocates them. Where a PDF shows the VAT number or the rate in a free layout, an e-invoice in the Peppol BIS Billing 3.0 format places each piece of information in a tagged field, read directly by the recipient's software.
The benefit is twofold. First, the mandatory details become automatically checkable: compliant software refuses to send an invoice that is missing a required field. Second, identifying the parties relies on the same enterprise number, used as the routing address on the network. To understand this format, see The UBL 2.1 format explained; for the Belgian calendar, Peppol in Belgium: the B2B mandate on 1 January 2026.
Further reading
- Invoicing in Belgium: rules and obligations: the general framework beyond the details alone.
- E-invoice or PDF: what is the difference: why content matters more than the medium.
- Peppol in Belgium: the B2B mandate on 1 January 2026: who is in scope and from when.
The reference sources are authoritative: Article 226 of Directive 2006/112/EC and the guidance of the FPS Finance.
What are the mandatory invoice details in Belgium?
An invoice must show the date of issue, a unique sequential number, the supplier's identity and VAT number, the customer's identity (and VAT number in B2B), the description and quantity of the goods or services, the taxable amount per rate, the VAT rate and amount, plus any wording justifying an exemption or the reverse charge. The list is set out in Article 5 of Royal Decree no. 1.
Is the VAT number mandatory on an invoice?
Yes. The supplier's VAT number is always required. The customer's VAT number is mandatory when the customer is itself a taxable person, notably in B2B and for intra-Community supplies.
When must the wording "reverse charge" appear?
When the VAT is due by the customer rather than the supplier, the invoice shows no VAT amount but carries the wording "Reverse charge". This applies, for example, to certain construction work between taxable persons and to intra-Community supplies of goods.
Is an invoice missing mandatory details still valid?
An incomplete invoice exposes the customer to a denial of VAT deduction and the supplier to administrative penalties. It can still be fixed: the supplier can issue a corrective invoice or a supplementary document carrying the missing details.
Do the mandatory details change with Peppol e-invoicing?
No, the legal details stay the same. A structured e-invoice in the Peppol BIS Billing 3.0 format carries the same information in tagged fields, and compliant software automatically checks that each one is present before sending.
