In August 2015, Mills released his mixtape titled SubTrap. The name stands for Suburban Trap or "Trap music with substance." The album features the singles "The Plug," "God Said Trap (King Trappy III)" and "Cookie Addiction" featuring BJ the Chicago Kid. It features production from Skhye Hutch, was mixed by Lo Mein, Tim Webberson, Matt Weiss, and Delbert Bowers. Project management for Subtrap was overseen by Blade Thornton, David Kuti, Clayton Barmore, Quinelle Holder and Ryan Booth. Mills' style of rapping has been compared to the early work of Kendrick Lamar, especially Lamar's 2011 album Section.80.
On June 22, 2016, Mills was announced as one of the performers at the 2016 Trillectro Music Festival. On September 9, 2016 Mills released his album Empty Bank and premiered it on Forbes Magazine. The album addresses having financial issues, an anxiety Mills wanted to tap into because it is widespread and taboo in the American mindset. Mills opened for Isaiah Rashad on his "The Lil Sunny" tour which started in January 2017.
On October 13, 2017, Mills released his debut studio album, IWasVeryBad, which was released through Adult Swim.