All banks check and have the right and obligation to check the origin of the assets of their customers pursuant to the Money Laundering and Terrorist Financing Prevention Act. The bank is obliged to understand how the client has earned the existing assets, and, in certain situations, the origin of the assets used in a specific transaction. When you receive the respective letter from the bank, the easiest thing to do is explain in your response to the bank how you became the owner of the money and, if possible, enclose the documents that prove this. Such documents may be a statement of your account in another bank, a purchase and sales contract, succession documents, loan agreements, etc.