Over £7000 held in credit!

dunstonh

The original post was clear that the money was returned eventually. It's easy to blame the firm, because it's their fault.

These two items are not compatible. The bill and the amount you pay are separate. If you pay more than the bill, you will receive a refund.

Why do they need a credit balance of £7k even if the £400 a month was accurate. It's still 18 months worth of energy.

That decision rests with the account holder. Eventually, the energy company would have identified it, but they don’t review every account each day. Upon the account holder’s death, duties pass to the executor. And as mentioned above, the true reading is only known once the meter is read. We don't know how long the readings had been on estimates.

If the executor is a family member, then checking all the utilities could easily have been missed off their list of jobs to do, but that's no excuse for any company to be charging £400 a month for someone who is 7k in credit.

Again, you are overlooking a key point. A direct debit is drawn from a bank account. Upon death, for a sole account, all direct debits are cancelled. The direct‑debit cancellation notice would read: “Mandate cancelled due to death.” This informs the energy company of the reason. Therefore, the energy company would not have identified this area because the executor did not inform the bank. Even if they miss something, the bank account is not typically one of the things to miss.

My dad was with BG for energy at the time and their bereavement team were spot on dealing with his accounts. 

The bereavement team’s involvement indicates that someone has informed them of his death. That does not appear to have occurred in the op’s case. Or rather, not until over a year later.