An energy company threatened to take a Manchester man to court - over an "unpaid" bill for £0.00p.
Dave Abrams, of Wythenshawe, was astonished when he received the letter from Powergen, reports The Daily Mirror.
Mr Abrams, who is in his 50s and lives alone, switched energy providers from Powergen to npower several months ago.
He heard nothing from Powergen until the legal warning notice came through the door.
The letter, dated October 19, warned Mr Abrams he owed the company £0.00 for gas and electricity and said if he did not pay up he would be visited by a debt collection agency.
It added that he could also be taken to court and, as a result, may find it difficult to obtain credit in future.
Mr Abrams said: "I was a bit nonplussed when I received the letter. I couldn't understand why they'd sent it, as I was on a pre-pay meter."
Powergen confirmed the letter had been sent out in error - but said Mr Abrams actually owed the company £502 after paying too little for his energy when the price went up.
But a spokeswoman said: "We have now withdrawn the balance because we made the mistake by not calibrating Mr Abrams' meter."
