The AI wrote it in English. In Flanders, that document is void.

Belgian companies adopt AI in English, because the tools, the prompts and the examples are all in English. Then someone uses it to draft an employee warning, a job description, a policy, an evaluation form — and produces a document that has no legal existence.

The rule

Language use between employer and employee is regulated by region, not by company preference and not by what the employee speaks:

• Flanders: Dutch.
• Wallonia: French (German in the German-speaking area).
• Brussels-Capital: depends on the employee's language.

The rule attaches to the location of the operating unit, not to the employee's nationality, the company's working language, or what everyone in the meeting actually speaks.

What "void" means in practice

Under the Flemish decree, a document in the wrong language is null. A judge establishes the nullity and orders replacement, and until it is replaced the document is deemed never to have existed.

Read that against a dismissal file. The warnings you carefully documented did not happen. The performance record that justified the decision is not in evidence. You are arguing a case with nothing behind you.

The nullity is also one-directional in the employee's favour. It may not harm the employee: under the majority case law they can rely on a clause in the void document that favours them, while invoking nullity against one that does not. So the risk is entirely yours.

On top of that sit fines — criminal fines of €400 to €4,000, or administrative fines of €100 to €1,000.

There is a genuine exception: the Court of Justice of the EU found the decree conflicts with free movement of workers for cross-border employment contracts, and Belgian courts apply that. It is narrower than most people hope.

Why AI makes this worse rather than better

Three reasons, and they compound:

1. English is the default. The assistant answers in the language of the prompt, and the prompt is in English because the examples were.
2. Volume. A generated warning letter takes two minutes instead of forty, so ten times as many get written — and a defect that used to appear once a year now appears monthly.
3. It reads well. A fluent, professional, correctly-formatted document does not look like a document with a legal defect. Nobody proofreads it for the one thing that is wrong with it.

What to do about it

Put the language in the tool, not in the training. If a skill drafts employee-facing documents, it should take the operating unit as an input and produce Dutch or French accordingly — not produce English and rely on someone remembering to translate. Anything you rely on a human to remember every time will fail at the rate humans forget.

Separate the two jobs. Drafting in English and translating is a different workflow from drafting in Dutch, and it produces different text. Belgian HR language has settled formulations; a translation from English reads like a translation, which is its own problem in a tribunal.

Decide which documents are in scope before you build. Employer-employee documents are covered. An internal analysis, a supplier email, a strategy memo are not. Draw that line once, in writing, rather than in each conversation.

Keep the human signature meaningful. Whoever signs is the one accountable for the language being right. If that person cannot read the output critically in the required language, the review is theatre.