Dane Gillespie, from Belfast, woke on Wednesday morning to discover £8.9million in his account – considerably more than there had been the day before.
The 18-year-old had been reminded by his mother, Caroline, to ensure that a cheque of £8,900 from his grandmother had been cleared by the building society.
Dane Gillespie had paid the cheque in at a Nationwide branch on Donegall Place in Belfast. But unfortunately for him, his millions only lasted a few hours – as the building society realised its error
But when the Belfast Met student checked his account he was shocked to discover millions of pounds had been dropped in.
Recalling her son’s shocked reaction, Caroline told Belfast Live: ‘My husband messaged me with the photograph of his bank account details. It took me a wee while to click.
‘He’s going to me, “I’m gonna order a Porsche” and I said, “don’t be daft, that’s not our money, we need to get this sorted.”‘
Unfortunately for the excited teenager – who had used the Donegall Place branch – the mistake was quickly realised and the building society issued a correction.
The youngster had only been a millionaire for a couple of hours before his account was back to normal.
Caroline said: ‘We couldn’t believe it. My son thought he was a millionaire for a few hours.
‘It’s as well he told us and didn’t go and blow it all. He’s only 18.’
A spokeswoman for Nationwide told MailOnline that Dane would not have been able to spend all the mistakenly added money.
She said: ‘The customer paid the cheque in at the branch and unfortunately the wrong amount was keyed.
‘The error was noticed straight away and the balance was corrected in a matter of seconds.
‘While the amount was shown on his balance, cheques do not clear straight away, so the funds were never in is account.
‘Sadly he may have to wait a little longer to buy the Porsche he wants.’