Joanne Bowen said her son, William, checked his account balance at a Lloyds TSB branch and saw the $4 million sum, The Daily Mail reported Tuesday.

"He had several friends with him and they confirmed the figure," Bowen said. "A couple of adults also saw it and one of them reported it to a cashier later in the day."

She said he withdrew $600 from the account and immediately spent the funds on some new clothes and an iPod.

Bowen said she went to the bank and discovered the account was showing up as overdrawn by $600.

"(The bank manager) said at first it could not be possible. But when he saw the records he said he could not explain it and it must have been a fluke with the ATM," she said.

She said William plans to pay the money back.

Lloyds TSB said the incident is being investigated.