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.
In the email, the energy supplier told customers that it "had a confession to make" and informed them of the "unintentional discount".
The energy firm told customers that the issue had something to do with "reading factors" and "unit flags" which meant customers had only been billed a "tiny fraction" of the gas they had used.
The email then reassured the customers affected that they would not now face a new bill for the missing gas charges from the winter months.
Instead, Octopus Energy was going to waive the bill as it was their mistake.
In the email, the energy firm said: "Don't worry about the gas we've already billed you for: that was our mistake, and we have no intention of re-issuing your bills or trying to charge you for it.
In its statement about the news, Octopus said the error related to customers with old gas meters which run with imperial measurements rather than metric ones – causing a temporary system error.
In its statement to the I paper, an Octopus Energy spokesperson said: “We spotted a system error affecting a very small group of customers with older gas meters which still used imperial measurements.
“The customers in question got a 99% discount on their gas usage for a short period of time over winter, which we have honoured up to their latest bill.
"Customers don’t need to worry, the error is now fixed and all those affected have already been contacted.”
The energy firm said that everyone affected by the mistake had already been contacted and had asked customers who did not receive the email to not contact Octopus to find out if they received the discount.
This is because the firm's phone lines are facing high demand from customers due to the current energy crisis and it needs to able to have the resources to help those struggling with their bills.
Mirror Money has contacted Octopus Energy directly for comment on this story.
