which SBI code must I enter in the insurer's questionnaire

The SBI code from the Trade Register, not your own assessment

The code you provide is the SBI code that is listed in the company's registration with the Chamber of Commerce, not a code you choose yourself based on what best fits the insurer's question. Insurers ask for the industry code to determine the risk profile — think of liability, cyber or business damage — and they typically verify this against what is officially registered. Entering a different code, even if it seems more substantively appropriate, is more likely to create discussion than clarity during a later inspection or claim.

If the company has multiple activities and thus multiple SBI codes in the Trade Register, the questionnaire usually asks for the main activity: the code that is registered first or as "main". If you are unsure which one that is, the extract from the Trade Register is the quickest way to check — the code is listed there exactly as registered. This aligns with the question in which sector is the enterprise activewhich appears in virtually every supply chain questionnaire and for which the same source applies. If the registration is outdated — for example following a change in business activities — updating it with the Chamber of Commerce is the proper course of action, not a correction only in the answer to the insurer.

Where the code comes from: the Trade Register Act

The obligation to register a company and its activities in the Trade Register, including the associated SBI code, follows from the Trade Register Act 2007. Because this is a legally established fact, this register is also the only source that should be used as an answer — not an interpretation of your own service provision. This puts the industry code in the same category as other identity details, such as the registration number under which the company is registered: they are fixed, verifiable facts, not choices.