bank wants to know where the money from the first deposit comes from

Origin of first deposit is part of customer due diligence

The bank does not ask this out of curiosity, but because customer due diligence under the Act on the prevention of money laundering and terrorist financing (Wwft) requires it. When opening a business account, the bank must determine where the first money comes from: the entrepreneur's own capital, a loan, an investment from a third party, or transferred balance from another account. This is separate from the question about the origin of the company's assets in the broader sense — which concerns the build-up of business assets as a whole, this specifically concerns that first transaction.

What the bank usually wants to see is a document that proves the source: a bank statement from the account where the money came from, a loan agreement, a notarial deed for capital contribution, or a shareholders' resolution for a capital deposit. If you do not have that supporting document readily available, the common answer is a brief description of the source plus an undertaking that the underlying document will follow. An empty field or "n/a" is often seen by banks as incomplete, even if the amount was small. Where a deposit is connected to the shareholding structure, it is logical that the same questionnaire also asks about the beneficial owners of the company — those two answers must match each other, otherwise a new question arises.

Where this follows from: the client due diligence under the Wwft

The obligation to investigate the origin of funds stems from customer due diligence as set out in the Wwft: banks must not only know who their customer is, but also have an understanding of the cash flows associated with the account. The information registered in the Trade Register — such as under the Trade Register Act 2007 — gives the bank the basic picture of the company, but says nothing about the source of a specific deposit. The latter must be demonstrated separately, and that is precisely why this appears as a separate question alongside questions about UBOs, sanctions lists and creditworthiness.