> If you are a money launderer are you going to make an accurate disclosure? How does the US/Authorities check the validity of these disclosures?

Someone has to file the paperwork. If you willingly misfile it, then you are an accomplice. The various offices that manage these papers also try to do minimal checks. Also if the filer is a professional agent/attorney they have strict requirements to keep various details about their clients. (Which are protected by attorney-client privilege, but if there's sufficient evidence then a judge can issue a warrant, so the investigation can try to follow the trail. So either the attorney was duped or it was complicit.)