Here is the detailed, timeline-based guide to when Louis achieves (and loses) the title of Senior Partner. Louis Litt officially becomes Senior Partner for the first time in Season 5, Episode 10 ("Faith") , which takes place approximately 5 years into the show's timeline.
This is a reference to the legal drama (and its sequel series Suits LA ). The character Louis Litt (played by Rick Hoffman) has a long, complicated journey to becoming Senior Partner. when does louis become senior partner