The company agreed to make payments to compensate customers affected by additional bank charges and pay an additional 627,312 pounds to the energy redress fund, Ofgem added.

The majority of the affected payments were due to be taken in January 2021, but E.ON erroneously took payments on Dec. 24, 2020, due to a technical fault after a system change, the regulator said.

"This failure is a reminder to suppliers that when making changes to their systems, they need to undertake appropriate checks to avoid any unintended consequences for customers," Ofgem said.

E.ON reported the issue to Ofgem on Dec. 24 and has since also made redress and goodwill payments totalling 55,039 pounds to customers who contacted the supplier to say they had suffered additional bank charges, out of pocket expenses or other detriment, as a result.

Customers who have been affected and have not yet contacted E.ON should do so, Ofgem said.

($1 = 0.7179 pounds)

(Reporting by Nora Buli. Editing by David Goodman and Mark Potter)

By Nora Buli