The mrs(who works for an energy supplier)says: 'Have you been getting quarterly statements? I'd go through those and check the readings on them and check the balance of your account, it is possible that if your payments haven't been covering what you've been using that you could have built that much debt over the year(average spend for gas and electric now is around £1000-£1200 a year) this should show a gradual increase in the debit ammount. Also check whether its the gas or the electric that's in debit as it's possible that a faulty boiler/electrical device could cause an increase in usage. How long have you lived there? If it is just for the last year it's possible that your move in reading was wrong and you've been billed for too much. Did you take a reading when you moved in? If your renting your estate agent should have copies of the move in readings. If it is a correct bill you don't have to pay it in one go, they will spread it over up to 12 months for you. If you need any more help let me know'