Belgian Address Verification for SMEs: Cut Returns Fast

The hidden cost of wrong addresses

When you send 200 letters and 15 come back marked "Undeliverable", you lose more than 15 stamps. You also lose:

the 15 contacts — customers or prospects — you thought you had reached,
the time spent processing returns (opening, identifying, updating the CRM),
the perceived value of a reminder that never arrives,
sometimes a legal stake when a registered letter does not reach its destination (deadline blocked).

For an SME sending 1,000 to 5,000 items a year, the undeliverable rate is one of the least tracked and most expensive KPIs. If you send large batches regularly, our guide on bulk mailing for Belgian SMEs covers the full dispatch workflow from file preparation to post office drop-off.

What a correct Belgian address looks like

A clean Belgian postal address has five elements in a standardised order:

Recipient: person name or company name.
Complement (optional): department, floor, trade name.
Street + number + box: Rue de la Loi 12 bte 3.
Zip + locality: 1000 Bruxelles.
Country: Belgium (omit for national mail).

The Belgian postcode is a 4-digit integer between 1000 and 9999, no space or dash. A "B-1000" coming from a German ERP is an anomaly to fix.

The box number ("bus" in Dutch, "bte" in French) is too often missing on company addresses. Without it, an item intended for the law firm on the 3rd floor can land in the building's general mailbox.

The most common anomalies

In real CRM data, we always see the same issues:

Missing or non-numeric postcode ("B-1050", "1050 BXL").
Locality spelled in the other language (Brussel vs Bruxelles, Liège vs Luik). bpost accepts both, but your recipient prefers their own spelling.
Number and box fused together ("12/3" instead of "12 bte 3"). Often auto-fixed, not always.
Truncated addresses: line 1 cut at 30 chars in an old SAP system.
Companies that moved: the latest up-to-date address is rarely in the CRM — it is in the Crossroads Bank for Enterprises (CBE).

Reflex: cross-reference the CBE for business addresses

For a letter to an individual, you depend on the quality of your file. For a letter to a Belgian company, you have a public source of truth: the CBE. Each company has a registered office and active branches listed there.

Concretely, cross-referencing a business address against the CBE lets you:

check the company is still active (status "active", not "removed"),
pull the latest published official address,
spot a merger or transfer to another legal entity.

Bjet24 does this cross-check automatically when you enter a company number or when the system detects one in the imported CSV.

What Bjet24 checks automatically

On file upload or manual entry, Bjet24 checks:

postcode format (4 digits, valid range),
zip ↔ locality consistency (a 1000 must belong to Brussels, not Antwerp),
presence and plausibility of street number and box,
duplicates within the batch (same recipient at same address),
CBE status when a company number is provided.

Flagged rows come with a suggested fix; you stay in control to validate or exclude them. Businesses that also handle inbound correspondence can reinforce address quality at the reception stage with an inbound mail digitisation workflow for SMEs, which captures and structures sender data automatically.

Three habits that lower your undeliverable rate

Keep a single address master in the CRM and clean it quarterly. The longer you wait, the higher the cleanup cost.
Make the box number mandatory for recipients in buildings (web form, customer card).
Plug a verification service at the data entry point: it is far cheaper to fix 200 addresses on signup than to chase 200 after 3 years. If your system allows programmatic control, the Bjet24 API guide for developers shows how to validate and send in a single API call.

Summary

The bad reflex is to launch a mailing and discover the problems on the returns. The right reflex is to check upstream: format, consistency, CBE cross-check, duplicates. Five minutes of validation at upload time save you a week of returns and increase the share of items that actually reach their recipient. See how sending letters with Bjet24 works — no installation, no contract required.

Frequently asked questions

How do I verify that a Belgian postal address is correct?

A correct Belgian postal address includes a 4-digit postcode between 1000 and 9999, a locality consistent with that postcode, a street number and, where applicable, a box number (bte or bus). For company addresses, you can cross-reference against the Crossroads Bank for Enterprises (CBE), which publishes the registered office and active branches of every Belgian company. A service like Bjet24 performs this check automatically when you import a file.

What is a valid Belgian postcode?

The Belgian postcode is a 4-digit integer between 1000 and 9999, with no space, hyphen or prefix such as « B- ». It must match the stated locality: for example, 1000 belongs to Brussels, not Antwerp. A postcode written as « B-1050 » or « 1050 BXL » is an anomaly that should be corrected before sending.

Why do mail items come back marked as undeliverable?

The most common causes of undeliverable returns are: an incorrect or inconsistent postcode, a missing box number for a multi-unit building, a company that has moved but whose address was not updated in the CRM, or a truncated address field. An undeliverable rate of 5 to 10 % is typical in uncleaned files; upstream verification significantly reduces this figure.

How does the CBE help verify a Belgian company address?

The Crossroads Bank for Enterprises (CBE) is the official register of all Belgian companies. For each active entity it publishes the registered office and branches with the current address. Cross-referencing an address against the CBE lets you detect a move, a merger, or a deregistration. This can be done manually via the public portal or automatically through integrated services.

What is the difference between a street number and a box number in a Belgian address?

The street number identifies the building (e.g. 12); the box number (bte in French, bus in Dutch) identifies a separate space within the building, such as a flat, a floor or an office (e.g. bte 3). For company addresses in a shared building, the box number is essential: without it, mail may be deposited in the communal letterbox or returned to the sender.