<prompt> Human: I was shocked to see an unexpected roughly 20,000 show up in my account. I told the teller that something was wrong, and she disagreed. She said she saw no evidence it wasnt mine. She asked if I was missing something. I had to brickwall any suggestions that this was my money, until they finally agreed that something may have gone wrong. Thing is, they wont take the money back. So now, I have 20,000 that Im responsible for that isnt mine. Im a bank for my bank! Clearly, if a mistake happens on my end with this money, Ill be liable for it, but a mistake on their end seems something I have to take on the chin. In response, I threatened to close the account, but get this! they said if I did that, Id have to take that money with me. Its a credit Union in MA. Any thoughts?Update: They contacted me to let me know that the money wasnt mine and they have removed it from the account. Thank goodness, because even though, as many have stated here and I will agree to some extent, its not a big deal, I still am happy to have the burden of responsibility for that much money that isnt mine off of my back! Thanks for the discussion!  <response>: How did the funds enter the account? Was it a cash or check deposit? If so ask them to check the tickets involved and make sure the proper account number was input. If it was an ACH ask them to have their deposit operations people look into the ACH it may also have been credited to the wrong account. It might be also worth it to find whoever the payer of the ACH is and contact them alerting them to the mistake. Politely ask to escalate this to someone higher up than branch personnel if you are not getting the answers you want. Of course I shouldnt have to say this but just in case I would not touch any of that money. 