Tanner serves as the commissioner of the Georgia Department of Behavioral Health and Developmental Disabilities.

[5] Tanner is strongly anti-abortion, and voted in favor of the "fetal heartbeat bill" in the state House.

[7] In 2016, Tanner sponsored legislation to regulate the use of unmanned aircraft systems (drones) in Georgia.

[8] In 2016, Tanner was the lead sponsor of legislation to allow businesses to refuse services to same-sex couples on the basis of religious beliefs.

[13][10][14] The House legislation, which passed 104–70, also included a jet fuel tax break for airlines and a rural transportation package.

[15][16] He vowed to combat what he asserted to be "attempts to overthrow an election through this impeachment nonsense, socialists running for president, a resistance to support President Trump in building the wall, and Nancy Pelosi and the Socialist Squad trying to destroy our values.

[18] Following Governor Kemp's election to a second term, Tanner was selected to serve as the commissioner of the Department of Behavioral Health and Developmental Disorders.