why does the bank want to know how much cash I receive

Cash is a money laundering risk indicator for the bank

The bank asks this because a high share of cash turnover is more often associated with money laundering risk, and the bank is required to assess that risk as part of customer due diligence under the Act on the Prevention of Money Laundering and the Financing of Terrorism (Wwft). Cash is harder to trace to a source than a bank transfer, and therefore the bank wants to know whether the share of cash in your business is consistent with the nature of your activity. A hospitality business with high cash sales is different from a consultancy that would report 40% in cash — the latter is a red flag, not necessarily a problem in itself, but something the bank wants an explanation for.

What the bank asks for specifically varies by institution: sometimes a percentage, sometimes an estimate in categories ("less than 10%", "10-25%" etc.), sometimes an explanation of how that percentage is determined. If you do not have cash administration that shows this percentage directly, a substantiated estimate based on your accounting is usually sufficient — the bank does not expect an accountant's statement, but a plausible answer. This question is often linked to other questions from the same customer due diligence, such as the source of the company's assets and at which banks the enterprise maintains accounts — together they form the picture the bank needs to establish your risk profile.

Basis: client due diligence under the Wwft

This question follows from the customer due diligence obligation in the Wwft: banks must establish the nature and purpose of the business relationship and make a risk assessment, and the share of cash turnover is a standard indicator for this. This is separate from the question about the ultimate beneficial owners of the company, which follows from the same law but fills in a different part of the client picture: not the transaction risk, but the ownership and control structure.