SIX said the fine related to UBS's announcement of a strategy change in October 2012 to scale back further in investment banking, which followed related reports in the media.

"The company was not authorized to postpone the announcement while awaiting the decision of its board of directors, i.e. until the morning of 30 October 2012, because a potentially price-sensitive fact already existed prior to the board's decision and the conditions for a postponement of disclosure were no longer given," SIX said on Wednesday.

Listed companies must immediately make an ad hoc announcement following the leak of price-sensitive information to the public, SIX said, and UBS should have made a statement no later than Oct. 29.

The Swiss Federal Supreme Court's decision not to hear UBS's appeal request meant a ruling handed down by the bourse's Court of Arbitration on March 22, 2016 became final.

In an emailed statement, UBS said the Supreme Court "did apparently not recognize the significance of this case and for formal reasons did not see the necessity to establish legal clarity."

"UBS continues to believe that it was and is appropriate to issue an ad hoc announcement only after a final approval of the strategy by the Board of Directors," UBS, Switzerland's biggest bank, said in a statement.

(Reporting by Brenna Hughes Neghaiwi and Joshua Franklin. Editing by Jane Merriman)