why do I have to account for where the money for starting the business comes from

Origin of start-up capital is part of customer due diligence

The bank does not ask this out of curiosity, but because the Act on the prevention of money laundering and terrorist financing (Wwft) requires it to know where a customer's money comes from. That customer due diligence applies not only at the start of the relationship, but also later, for example with a capital deposit, a loan from a shareholder to their own private company, or a sudden increase in equity. This subject overlaps with the source of the company's assets: banks and sometimes also insurers pose this question in virtually identical form, only with a different format.

In practice, the bank asks about a concrete event: a deposit of personal savings, a family loan, a purchase of shares, a business credit. The supporting document that goes with it is usually a bank statement of the deposit, a loan agreement, or a notarial deed for capital contribution. If you do not have that at hand immediately, it is more usual to leave the question open than to give an answer that you cannot substantiate. With a private company with multiple shareholders, this question often also who the ultimate beneficial owners of the enterprise are, because the bank usually assesses the source of capital and the ownership structure in one go.

Basis: AML client due diligence, not the Commercial Register

The obligation to conduct this due diligence is set out in the Wwft and is an obligation of the bank as an institution in its own right, separate from what has already been established with the Chamber of Commerce under the Trade Register Act 2007. The Trade Register records who operates an enterprise and who is authorised to do so, but not where the money comes from — that is precisely the gap that the customer due diligence of the Wwft fills.