What to do if extra cash turns up in your bank account.

Ever been given the incorrect change at restaurant? Perhaps an extra $5 here and there? Well, how about being mistakenly given $5 million?

Bank errors on that scale might not be all that common in this day and age, but they do happen. Just ask that (un)fortunate Sydney woman who was arrested overnight, four years after $4.6 million was accidentally transferred into her account.

The 21-year-old was caught attempting to flee to Malaysia, and formally charged with dishonestly obtaining financial advantage by deception as well as knowingly dealing with the proceeds of crime.

See despite what that little Community Chest Monopoly card might have told you, a “bank error in you favour” does not mean you get to collect.

via NBC

Kat Lane, Principal Solicitor at the Financial Rights Legal Centre, says she frequently gets calls from people asking if they can spend money mistakenly transferred to them.

"It must be so tempting," she told Mamamia. "But the answer is always 'no'. You don't get to take other people's money that they've given to you by mistake."

So what should you do if you spot a bonus credited amount on your statement? The first step is simple: Put your hand up.

"We would always recommend that if you see an amount in your account that you don't recognise that you report it to the bank immediately," a Commonwealth Bank spokesperson told Mamamia.

Sadly, not only are you not allowed to keep the coin, you have to dob it in.

"You're not expected to look at every single thing in your bank account," said Lane. "But it's important that if any money comes in and you don't know what it is, just be very careful about not spending it."

That could see you prosecuted on charges such as those levelled against the Malaysian-bound accidental millionaire. However, in most small-time cases, you'll simply be required to pay the money back.

"If it's a small amount and you spend it by mistake there's usually no [legal] repercussions. You just repay it," said Lane.

But beware that the bank and authorities aren't likely to be as forgiving with large sums. Particularly if you try to skip off overseas.

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Of course, there are limitation periods on how long the payer has to recover the money. Generally six years, according to Lane, depending on which state or territory you're in. But it's highly unlikely that you'd be able to avoid detection for that long anyway.

The simple truth is if you only fancy wearing handcuffs in the bedroom, then do the right thing: Call the bank, report it.