I managed to get it to work by including an IF function:
CY =
VAR CURRENTITEM = TRIM(SELECTEDVALUE( ‘Summary P&L template’[Income Statement Items] ))
RETURN
SWITCH( TRUE() ,
CURRENTITEM = “Total Revenues”, CALCULATE( [Subject IS], ‘Subject Hotel Summary’[Items (Normalized)] = “Total Revenues”) ,
IF(Metric[Table Data] = “% TORE” , FORMAT(CALCULATE( [Subject IS] , FILTER(‘Subject Hotel Summary’ , ‘Subject Hotel Summary’[Items (Normalized)] = CurrentItem)) , “0.0%”) , CALCULATE( [Subject IS] , FILTER(‘Subject Hotel Summary’ , ‘Subject Hotel Summary’[Items (Normalized)] = CurrentItem))))