bank asks questions about a large payment on my account how do I respond

Origin and purpose of the transaction, not the bank itself

The bank is not asking this out of curiosity, but because the Act on the Prevention of Money Laundering and Financing of Terrorism (Wwft) requires it to conduct customer due diligence whenever a transaction deviates from the normal pattern. Usually it wants to know two things: where the money comes from and why it is coming in now, in this amount. That is a different question than with an insurer or in a sustainability questionnaire — why a bank asks something different than an insurer when it is about the same subject is precisely this difference in purpose.

As an answer, a short, factual description usually suffices: which agreement or invoice underlies the payment, who the counterparty is, and a copy of the underlying document — invoice, contract, or sales agreement. If you don't have that at hand, answer that you will look it up instead of filling in something you cannot substantiate; a guess that later turns out to be wrong is more troublesome than a day's delay. Origin of assets, moreover, is a broader question than just this one transaction — if the bank asks for that separately, it is about the source of the company's assets, not about this specific payment.

Basis: the customer due diligence from the Wwft

These questions arise from the customer due diligence that the Wwft imposes on banks: they must assess unusual transactions and report them if necessary, and for that they must be able to understand the background of the money. That is separate from the trade register — the Trade Register Act 2007 establishes who represents the enterprise, but says nothing about the origin of individual payments. If the question comes together with a request to confirm the UBOs, that is about another part of the customer due diligence; see for that who are the ultimate beneficial owners of the company.