It's a cliche that dates back to Monopoly: A bank error in your favor leaves you with an unexpected windfall. But for Parijat Saha, an Indian schoolteacher, the Community Chest card came to life in a big way when he discovered that his bank account suddenly held $9.8 billion.

"I was expecting an amount of a little more than 10,000 rupees ($200)," Saha told the BBC. The teacher, whose monthly salary is roughly $700, was stunned to find his account filled with a Buffett-level balance. He quickly notified bank officials, who subsequently announced that the huge sum was listed as "uncleared," which means that Saha couldn't have withdrawn it.

Saha's honesty is commendable, but it raises an interesting question: What should bank customers do when they find themselves the beneficiary of a bank error?

The other route, grabbing the money and hitting the road, can be alluring -- for awhile. In 2009, a New Zealand couple, Leo Gao and Kara Hurring, were surprised to discover that a bank error had left them with a $6.2 million overdraft account. The two quickly withdrew about $2.3 million and went on the lam. In 2011, Hurring voluntarily returned to New Zealand, and Gao was arrested a few months later. She's scheduled to go on trial in February and he is being held pending a bail hearing.

While among the most impressive accidental millionaires, Gao and Hurring are hardly the only people who have found themselves on the wrong side of the law after falling victim to the temptation to take advantage of a bank's blunder. In 2008, Pennsylvania couple Randy and Melissa Marie Pratt used a bank mistake to make off with $177,250. They were later apprehended in Florida, and ended up behind bars. Similarly, when Susan R. Madakor, a Brooklyn, N.Y., woman, spent part of a $701,998 windfall that mysteriously appeared in her Chase Manhattan account, she ended up doing two years in prison for bank larceny and bank fraud.

But bank error stories don't always end up quite so badly. In 2007, Harriet and Herbert Starbird, another Pennsylvania couple, spent about half of $280,276 that their bank erroneously deposited in Mr. Starbird's account. When the case came to court, they were forced to repay the money, but didn't end up doing time. While there are several reasons that Herbert Starbird got off relatively easily, the fact that he didn't try to flee and repeatedly tried to return the money likely factoring in heavily.

The moral is clear: if you see a mistake in your balance, contact your bank immediately. The statute of limitations on bank errors that benefit customers can vary from state-to-state, but most jurisdictions give banks several years to discover their mistakes and seek restitution. And, needless to say, customers who spend their ill-gotten gains will likely find themselves facing the wrath of hordes of well-paid bank lawyers.

Bruce Watson is a senior features writer for DailyFinance. You can reach him by e-mail at bruce.watson@teamaol.com, or follow him on Twitter at @bruce1971.