The watchdog, Ofgem, said the disclosure breach relating to capacity at the Fiddler's Ferry power station under SSE's contract with National Grid could have had a "significant effect" on wholesale electricity rates.
SSE in a separate statement said their approach was not in line with Ofgem's requirement for disclosure to the market at an earlier stage. (https://bit.ly/32VkfWb)
OFGEM said that although the company had not "acted in bad faith," the fine "sends a strong message" to all entities in the energy market.
SSE qualified for a 30% discount on the predicted penalty because of early settlement and its cooperation during the investigation, the watchdog said.
The fine was the first of its kind in Britain and Europe for failing to disclose inside information in an "effective and timely" manner under the Regulation on Energy Market Integrity and Transparency (REMIT), it added.
(Reporting by Pushkala Aripaka in Bengaluru; Editing by Shailesh Kuber and Devika Syamnath)