Hundreds of customers of the collapsed firm Together Energy have wrongly been charged a £40 exit fee after being moved over to British Gas.
Households on a fixed tariff are now being urged to check their final statement in case they’ve been incorrectly billed.
It comes after Together Energy collapsed on January 18, leaving 176,000 homes without an energy supplier.
British Gas was later appointed by Ofgem to take on its customers from January 28.
The energy giant has told customers who’ve been affected that they won’t need to pay the charge, and confirmed the fee has not yet been taken.
Households should be sent a new bill with the correct charges, according to Money Saving Expert, which first reported on the error.
New supplier British Gas claims around 800 Together Energy customers were affected.
A British Gas spokesperson told MSE: "We’ve spoken to Together Energy’s administrators and they’ve confirmed this is a mistake impacting a small number of customers transferring over to us.
“The final bills which they issued showing the exit fees will be removed and customers will see this replaced with the correct bill."
Have you been wrongly charged an exit fee for leaving an energy supplier? Let us know: mirror.money.saving@mirror.co.uk
Since the beginning of 2021, more than 30 energy companies have ceased trading due to soaring wholesale gas prices.
Rising costs have also seen the regulator Ofgem push up its price cap by hundreds of pounds from April.
Ofgem has confirmed it is increasing its price cap by £693 from £1,277 to £1,971 for those who pay by direct debit- up by 54% and a huge hit to household bills.
Prepayment customers will be worse off, with a jump of £708 from £1,309 to £2,017.
The energy price cap sets a limit on the rates a supplier can charge for each unit of gas and electricity you use and is currently reviewed twice a year.
How to get help with your energy bills
If you’re really worried about your energy bills, you should speak to your energy provider first to see what support they can give you.
There are also lots of schemes you may be eligible for, particularly if you're in a low income household or claim benefits.
For example, there is the Warm Home Discount scheme, which offers £140 one-off payments for those who get the Guarantee element of Pension Credit or are on a low income.
There is also the Winter Fuel Payment scheme, where those getting the state pension can get between £100 and £300.
Low income households can also get £25 a week to help with energy bills during the winter thanks to the Cold Weather Payment scheme too.
You may also want to use the free grants search tool from debt charity Turn2Us to see what help is available where you live.
There are around 8,000 grants currently available.