Trillions

Scott Hardie | December 2, 2007
The most experience any of us has with a bank error is drawing that community chest card in Monopoly. But one poor guy got an automated letter from his bank saying that he owed $211,010,028,257,303.00. Talk about ruining your credit. (link)

Makes me curious: You discover a large sum of money in your bank account by mistake, let's say six figures or more, and the bank seems unaware of their computer error. What do you do?

We have at least two bankers or bank employees here, so this could be interesting.

Eric Wallhagen | December 2, 2007
They'll notice sooner or later if it's 6 figures and up. There's really no hiding from that one I don't think. Would they stick it to ya if you never said anything, and they discovered it 6 months later... Probably not, as long as the money is there to pay back to them. They can't penalize you for not pointing out their mistake though. So I'd say just sit on it, don't spend it, and if it's still there a year later (after the bank has closed the books on that fiscal year) then take it and run with it, because if they haven't spotted the error by that point, they probably never will. I can't imagine that it'd take them more than a day or two to spot that error and fix it though.

Something close to that happeend to me one time, I noticed an extra like 1000 bucks in my account... the next day it was gone... asked the bank about it and it was an error on their part. They notice those things pretty quick, I mean after all... Money is their business.

Steve West | December 2, 2007
All banks have internal balancing procedures that are rigorously monitored.

They'll notice next day if they have an Item Processing department (not all banks do and contract that to a larger bank to do it for them). Item Processing monitors check activity and maintains control over account balances by clearing and depositing check items. The Accounting department ensures that branch activity corresponds to account activity as far as cash transactions are considered and that branch activity corresponds to Item Processing activity.

The customer bears the burden of knowledge to maintain his/her own account. Any funds in the account are their responsibility for knowledge of:
1) how it got there and
2) whether they have a right to those funds.

It is always considered unlawful gain to keep funds not legitimately acquired even if it is the bank's error initially. Spending it is probably foolish as the law (although it varies slightly from state to state) sides with the banking institution for the return of those funds. The penalties can be severe depending on the dollar amount.