Octopus Energy has accidentally undercharged thousands of customers on their energy bills over the winter and has confirmed that those affected don't need to pay a penny back.
Customers received an email from the supplier last week saying they had only been charged just 0.1% of the amount of gas they have used over the last past few months.
This 99.9% undercharge was a result of an "obscure technical error" by Octopus Energy.
