Invoice numbering in Belgium: rules, series and credit notes

Every Belgian VAT invoice must carry a number that follows on from the previous one in its series and identifies that invoice, and only that invoice. The law lets you run one series or several, so a separate credit-note series or a counter that restarts each year is your choice. What you must never do is give two documents the same number, or change a number once your customer has the invoice.

This is the reference page for numbering in the OrdoGrid knowledge centre. It covers what the law requires, the choices it leaves you, how OrdoGrid assigns numbers, and how to handle year changes, deleted drafts, corrections and a move from another tool. For the other mandatory mentions, see Belgian invoice legal mentions.

What the law requires, and what it leaves to you

Article 5 §1 1° of Royal Decree no. 1 (the VAT invoicing decree) requires the issue date and ‘a sequential number, based on one or several series’ that identifies the invoice uniquely and under which it is entered in your outgoing invoice book. Simplified invoices need the same kind of number (art. 13). Credit notes and other rectifying documents are entered in the same book as the invoices they correct (art. 14 §2 2°), and must refer to the invoice concerned (art. 12).

Since 1 January 2025, businesses under the small-business franchise scheme are exempt from keeping the invoice books only if they file the invoices and documents they receive, issue or draw up in an uninterrupted series of classification numbers and keep the register of art. 14 §5 (art. 14 §4). That unbroken filing sequence is a condition of the exemption; it comes on top of the invoice's own sequential number. OrdoGrid keeps neither the filing sequence nor the register, so agree with your accountant how you file these documents.

Outgoing invoice book

The register (facturier de sortie / boek voor uitgaande facturen) in which a VAT-registered business enters every invoice and credit note it issues, under its number. Your accountant often keeps it as the sales journal.

Choose your series

Credit notes: same series or a separate one?

Both are lawful. RD no. 1 does not require a separate credit-note series; it requires a reference to the corrected invoice. We recommend a separate series such as NC-2026-0009: the invoice counter stays easy to check and credit notes are easy to find. It is also the only set-up OrdoGrid supports, because each document type has its own counter.

A partial credit note still gets its own credit-note number. Do not reuse the invoice number with a suffix such as ‘-bis’.

When the original was a structured e-invoice, the credit note must be issued in the same format, so in practice via Peppol (art. 53 §2bis VAT Code). OrdoGrid sends it as a UBL credit note whose billing reference (BT-25) carries the original invoice number. Peppol does not check whether a document duplicates an earlier one (FPS FAQ, Q4): spotting a reused or repeated number is up to you and your customer's software. More in credit notes on Peppol.

How OrdoGrid numbers documents

Document type names and most labels in the editor and settings are in French in every interface language.

Placeholders: {YYYY} year, {YY} two-digit year, {MM} month, {####} counter (the number of # sets the padding). Proposal quotes (Devis proposition) use {YYYY}-{CLIENT_SLUG}-{###} when the client has a Slug devis (quote slug). Quotes, receipts and payment requests never take invoice numbers.

Year and month come from the document's Date when OrdoGrid proposes the number (today's date when you open the editor), so a format with {YYYY} restarts at 0001 each year and one with {MM} each month. If you then change the Date to another year or month, N° is not recalculated: check it and correct it before the first save.

• Proposed: when you open Nouvelle facture (New invoice), OrdoGrid proposes the highest existing number in the same pattern plus one (Génération du numéro... appears meanwhile). You can overwrite it in N°.
• Committed: the number is stored the first time you save, even as a Brouillon (draft). Fix a saved draft; do not create a new invoice to get a fresh number.
• Unique: invoices, credit notes, receipts and payment requests share one pool per company. Saving a number that already exists fails.
• Not gap-free: typing F-2026-0150 after F-2026-0142 makes the next proposal F-2026-0151; the skipped numbers stay a gap.
• Deleting a draft with Supprimer (Delete) frees its number. Only drafts without payments, Peppol transmission, linked documents, payment link or an API external_id can be deleted. If it was the highest, the next document reuses it; otherwise its deletion leaves a gap.
• Locked: you cannot change a number while the document has attachments. Once a payment is recorded or a Peppol transmission is prepared, the number is locked with the financial content. Saved credit notes are locked too.

Change a numbering format

1. Open Profil entreprise (Company profile), tab Profil, section Paramètres de facturation (Billing settings). Owners and administrators can edit it; viewers cannot.
2. Under Formats de numérotation (Numbering formats), click Modifier (Edit) to unlock the fields.
3. Edit Format factures, Format notes de crédit, Format devis or Format reçus, or tick Année (Year) or Mois (Month) under Options d'affichage (Display options). Aperçu (Preview) shows the first number in the new format.
4. Click Sauvegarder (Save). Clicking Verrouiller (Lock) instead discards unsaved format changes.
5. Open Nouvelle facture and check the proposed N° before saving the first document.

A new pattern usually starts its own counter at 1, so a mid-year change creates a second series for that year. If the old numbers still fit the new pattern (for example when you only change the number of #), the counter continues instead; check the proposed N°. Change formats on 1 January where you can; otherwise note the date, the last number of the old series and the first of the new one.

Before and after sending: what may change under the same number

Traité in Peppol → Outbox means network delivery, not acceptance by your customer.

Worked example: Atelier Nord SRL

Atelier Nord SRL, a design studio in Liège, uses the default formats. Its last invoice of 2025 is F-2025-0188, dated 22 December 2025.

On 2 January 2026 it invoices December work for Imprimerie Dubois SA. The invoice is dated 2 January 2026, so OrdoGrid proposes F-2026-0001; the December period goes in the line Description. The deadline was 15 January 2026 (RD no. 1 art. 4: the 15th of the month after the chargeable event).

On 6 October 2026 it sends F-2026-0142 to Imprimerie Dubois SA via Peppol, and Peppol → Outbox shows Traité. On 7 October a draft F-2026-0143 for another client is dropped before anything is sent. It is the highest number, so deleting it lets the next invoice reuse F-2026-0143 without a gap.

On 8 October the client points out that 10 hours were agreed, not 12. F-2026-0142 is locked, so Atelier Nord selects it in Factures, clicks Note de crédit, sets the prefilled line to 2 hours and issues NC-2026-0009 on 9 October, referring to F-2026-0142 of 6 October 2026, then sends it via Peppol.

In the invoice's Settlement panel, Outstanding falls to €1,028.50. Neither number changed.

Moving from another tool during the year

No number may be issued twice, and anyone checking your books must see where one series ends and the next begins. OrdoGrid only knows the numbers it holds, so its first proposal in 2026 is F-2026-0001 until you act.

• Continue the same series (recommended). Set Format factures to the old tool's pattern, for example {YYYY}-{###} if your last number was 2026-041. Type 2026-042 in N° on your first OrdoGrid invoice; OrdoGrid then proposes 2026-043 and onwards. If the old tool already used F-2026-0041, just type F-2026-0042.
• Start a new series. Keep F-{YYYY}-{####} only if its numbers cannot collide with the old ones, and agree it with your accountant. Write down the switch date, the last old number and the first new one.

Do the same for credit notes. Do not retype old invoices with Nouvelle facture to move the counter: you would create a second record of invoices already issued. Keep the originals in the old tool's archive or export.

Importer (Import) on the Factures page is different: it brings in an issued invoice PDF with its original number and saves it as Envoyée (Sent) by default. Imported numbers that match Format factures count when OrdoGrid proposes the next number. Check that each import keeps its original number, and never send an imported invoice again by email or Peppol.

Common mistakes

For a draft that seems to have disappeared, follow recover a saved invoice before creating a new number. Quote conversions are covered in quote to invoice.

Evidence to keep

• Your outgoing invoice book or sales journal, usually kept by your accountant. OrdoGrid has no journal export; the Factures and Notes de Crédit lists (columns Number / Client / Amount / Date / Status) and their bulk Download button (‘Download as ZIP’) give you the documents.
• A numbering memo: each format change, each migration, and each missing number with its reason, for example ‘F-2026-0097: draft deleted 3 June 2026, never sent’.
• Peppol originals: in Peppol → Outbox, select the rows and download the ZIP with the XML and PDF.
• Retention: keep invoices and credit notes for 7 years from 1 January of the year after issue (art. 60 VAT Code, as amended by the Law of 18 December 2025); some documents linked to immovable property need longer. See invoice archiving.

FAQ

Must Belgian invoice numbers be consecutive without gaps?

The law requires a sequential number, in one or several series, that identifies each invoice uniquely. Avoid gaps and keep a written reason for any missing number, such as a draft deleted before it was sent. OrdoGrid does not enforce gap-free numbering, so that check is yours.

Can credit notes share the invoice series?

The law allows it, because it permits one or several series and does not require a separate credit-note series. OrdoGrid uses a separate series (NC-) for credit notes and links each one to its original invoice.

Can I restart numbering at 0001 every year?

The decree prescribes no format. With the year in the number, as in F-2026-0001, each number stays unique. OrdoGrid's default format restarts each year for this reason. Ask your accountant if your set-up is unusual.

I issued 41 invoices in another tool this year. How do I continue in OrdoGrid?

Set the invoice format to match the old pattern and type number 42 by hand on your first OrdoGrid invoice. OrdoGrid continues from the highest number in that pattern. Record the switch date and the last number issued in the old tool.

Can I delete a draft invoice and reuse its number?

Yes, if nothing left the company. Only drafts without payments, Peppol transmission, linked documents, payment link or an API external_id can be deleted. Deleting the highest draft lets the next invoice reuse its number; any other deletion leaves a gap to document.

Can I change an invoice number after sending it?

No. Once the customer has the invoice, its number is fixed. OrdoGrid locks it after a payment or Peppol transmission. To correct content, issue a credit note and, if needed, a new invoice with a new number.

Do quotes, receipts and payment requests use invoice numbers?

No. In OrdoGrid they have their own series (D-, R-, DP-). When a quote or receipt is invoiced, the resulting invoice takes the next number in the invoice series.

Can companies in one group share a counter?

Not as a rule. Unless the companies form a VAT unit, each one is a separate taxable person with its own outgoing invoice book and its own series. In a VAT unit each member still invoices with its own details, so keep a distinct series per member unless you agree another set-up with your accountant. In OrdoGrid, each company has its own formats and counters.