Proof of source of funds - who demands what from whom?

P.S. If one of our customers sells their property and the money is received by us due to the repayment of liabilities, we do not ask the buyer where the money comes from. What is important is that it comes from/through a German bank. And that can be €100,000,000 for a building (commercial).

As I said, I think there is a mix-up here. There are currently several news items like the EU abolishing cash. Then there is talk about proof of origin forms, but it is always about cash.

All your questions are very confusing and therefore hard to understand. If the money comes from a German bank and is deposited under your name into your current account and you pay the purchase price from there, no one asks questions. It becomes critical if the money comes from a different name and from abroad.

If the money is currently in a [depot] of a foreign bank and the tax office is possibly not supposed to gain insight, it will be difficult to use the money for the purchase.

If the money is currently in an account at a foreign bank and the tax office might not be allowed to have insight, it will be difficult to use the money for the purchase.

I believe there are only 11 or 12 countries in the world that do not transmit data to the German tax office, so don’t worry, they know exactly where someone has their money/account.

P.S. If one of our customers sells their property and the money is received by us due to the repayment of liabilities

And if they sell their property or securities which are then transferred by the stock exchange or its affiliated bank (Germany) - without repaying liabilities. Will there be an inquiry then?

Does the bank prefer to be informed in advance that a few hundred thousand euros will be received soon and why?