More than a million UK energy customers that switched providers could have been overcharged due to errors made by suppliers.
According to Ofgem, the sector's biggest suppliers made mistakes, including Ovo Energy, Shell, British Gas, E.On, EDF, Npower, Scottish Power, SSE and Octopus.
Ovo and Shell were identified as the worst offenders.
In total 18 suppliers made errors leading to excess bills totting up to £7.2m ($10m), according to a report by the BBC. The refunds, plus compensation have meant payouts of £10.4m.
When a customer switches supplier, the rules laid out by the energy regulator say that they are protected from price rises while switching. A switch can take up to three weeks.
These companies failed to protect customers that had switched tariff or supplier after price rises had been set between 2013 and 2020.
Anna Rossington, interim director of retail at Ofgem said: "Customers should have confidence in switching and not be overcharged when doing so.
"This case sends a strong message to all suppliers that Ofgem will intervene where customers are overcharged and ensure that no supplier benefits from non-compliance."
Natalie Hitchins, head of home products and Services at Which?, said: “It is right the regulator has intervened and sent a clear message to suppliers that this kind of behaviour is unacceptable. Firms must now act quickly to help affected customers, making it clear who is owed a refund and then doing so swiftly and without hassle.”
Which? says that switching is still the best way to save money, so anyone looking for a better deal or improved customer service should look to change suppliers – you could save more than £150 a year.
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