By Brian Milligan
Business reporter, BBC News
Claire Logie: 'It's very easy to do'
Claire Logie has a cartoon on her desk which says "stop and think" - a painful reminder of the day when she failed to do exactly that.
She had been meaning to transfer a sum of £2,000 into her savings account.
But, after clicking the wrong box, she accidentally sent the cash to someone she had paid years ago, and whose details had been saved on her account.
"As soon as I'd done it I felt sick and very upset," she said, but assumed she would eventually get the cash back.
But six months on she is still to receive a refund.
'Easy to do'
Claire is no online novice, and even works for one of the big four high street banks, so is familiar with banking on the internet.
She says: "I am not a dizzy person. I am not an idiot. I made the mistake, and it is very easy to do."
So, why will the bank not return the money?
The bank concerned, the Alliance and Leicester, says it cannot force the person who received the money to return it.
They tried repeatedly to contact the customer concerned, but "regrettably" that customer has not responded.
A spokesperson told the BBC: "It wasn't our mistake, so we are unable to take any further action".
Furthermore, they would not even tell Claire the name of the customer, because of the Data Protection Act.
That means she is unable to take the case to the small claims court.
The Financial Ombudsman is also unable to help, because her complaint is not against the bank itself.
Cases like this are rare, because most people receiving money by mistake pay it back.
But Jemma Smith, of the Payments Council, which oversees the efficiency of bank payments, admits there's nothing in the banking code about how errors like this can be dealt with.
The only answer seems to be not to make the mistake in the first place.
"Everything your bank will tell you is going to be stressing how important it is that you have the correct account name and sort code," she says.
Instances like this are not necessarily regarded as theft.
Legally this is a grey area, as proving the recipient of the money had a guilty mind at the time he or she received it could be difficult.
Imagine giving £2,000 to someone who looked like your friend on the street, but turned out not to be.
If they ran off with the money, would you have a leg to stand on?
The police told the BBC it might be possible for them to investigate, but they could not guarantee the Crown Prosecution Service would agree to prosecute.
Alison Steed, a former Daily Telegraph journalist who has set up a financial website called MyMoneyDiva.com, believes the problem is much more widespread than has been realised.
She estimates up to 1% of all bank transfers go astray.
That would mean as much as £439m being paid to the wrong person every year in the UK, although the vast majority of such payments would be corrected.
She also believes the Financial Ombudsman service should set up a department to deal with such mistakes.
"Part of the Ombudsman service could be in a position to look at these cases, and take on some kind of arbitration," she says.
But she is not optimistic about Claire getting her £2,000 back.
"I hope she gets it back. But I think in reality the chances are pretty slim."
In the meantime, for anyone doing some online banking, it might be worth remembering to stop and think.
Having that cartoon on your desk, and acting on it, could really save you money.