Around 2 years ago I did a post on what you should do if you found a bank had made a mistake in your favour; crediting your account with money that wasn’t yours.
The advice back then was to own up, as the financial obudsman and/or lawyers would rule in favour of the bank unless you could prove that you thought “in good faith” that the money was yours.
This has been illustrated by a recent court case where a woman was wrongly credited with £135,000, and she decided to go and spend it.
Sarah Jane Lee, 20, from Blackburn in Lancashire, had a bank balance of £6.59 when she discovered that a mistake by the Abbey bank had caused the figure to rocket to £135,000. She allegedly spent the money, giving tens of thousands to friends and buying a holiday, various appliances and a new sofa. But it’s now end-of-the-line time after she admitted “retaining wrongful credit” and 11 specimen charges of theft.
The BBC website has more information on the legal ins & outs, and there’s also some interesting stories in the comments. The basic advice is to report the error immediately, and to leave it unspent.