What I don't think it being said very explicitly in other responses is that it depends on the law and the circumstances. In the case of anti-money laundering l

What I don't think it being said very explicitly in other responses is that it depends on the law and the circumstances. In the case of anti-money laundering laws, my belief[0] is that it is very illegal to tell a customer they are being flagged. On the other hand, if it's a copyright thing, or some kind of contract dispute? You're normally totally free to tell the customer. [0] No professional experience involved, just a lot of reading patio11/Matt Levine.