why do I have to fill everything in again from scratch at a new bank

Every bank conducts its own customer due diligence

That is because every bank is required to conduct customer due diligence itself, and that investigation may not be taken over from another bank. This is called the customer due diligence under the Act on the prevention of money laundering and financing of terrorism (Wwft). The previous bank has built up its own file on your company, with its own risk assessment and its own records. A new bank cannot rely on that: they must conduct the customer due diligence independently, even if the questions and answers are virtually identical to what you filled in elsewhere before.

In practice, these are largely the same topics: who are the ultimate beneficial owners of the companyor one of the directors or interested parties a politically exposed person is, or if a sanctions list check is needed, and what the origin of the funds is. Every bank asks those questions in its own format and at its own time, but the underlying facts about your company do not change. That is precisely why it is useful to record those answers once in a supply chain file: not to take over the bank's obligation, but to make filling in each new application faster. See also how ubo data is filled in a questionnaire for the approach that banks expect in this regard.

Where this follows from: the Wwft and the Trade Register

The customer due diligence of the Wwft requires every bank to determine the identity and risks of a client itself, without being able to rely on investigation by another institution without its own verification. Some of the data, such as the directors and the registration of the company, are set out in the Trade Register on the basis of the Trade Register Act 2007 — but that register does not replace customer due diligence, it is merely one of the sources that the bank consults.