SSE has agreed to pay 1 million pounds for the submission of inaccurate and misleading annual statements to some pre-payment meter customers.
Regulator Ofgem found the energy giant sent 1.15 million of statements that are inaccurate and misleading than 580,000 customers between June 2014 and September 2015.
The guardian said that the problem had arisen as a result of a coding error.
An investigation was launched after SSE reported the matter to the regulator.
The company has reached an agreement for the payment of £1m in Ofgem’s fund consumer redress.
Ofgem found the annual statements that had incorrect information about the alternative cheapest tariff available to customers, and inaccurate estimates of how much they could save annually by switching to them.
Some of the statements also overestimated the annual savings that customers can make by changing their pre-payment meter to a standard credit meter payment by direct debit, as well as by the movement of the electronic billing.
The watchdog also said SSE was not able to act quickly to resolve the errors.
He added, however, that the impact on customers was “minimal”, as only a small proportion of households would have acted on the information by the change.
Ofgem confirmed that SSE had since improved its processes to avoid errors in instructions re-issued, including extra checks in the communication with the client.
SSE director of customer service operations, Gareth Wood, said: “we deeply regret the historical problems we have identified with some annual statements, for the pre-payment of the customers, relating to a coding issue, between 2014 and 2015.
“We proactively reported this to Ofgem once it is realized and, as Ofgem has acknowledged, we have done the right thing and now have two more measures to ensure that does not happen again.
“Although we are disappointed that do not meet the high standards expected of us in this example, we are pleased that the matter has already been closed with a voluntary payment that will directly benefit vulnerable customers.”