Tanner is expected to get as much as a year in prison at his sentencing, set for Nov. 20.
The 34-year-old actor was charged in April with selling 16 Social Security numbers and three bogus Social Security cards.
Tanner plays the character Skills in the CW series. Representatives for the network didn't immediately return a telephone call Saturday.
Tanner also appeared in the 2005 movie "Coach Carter," starring Samuel L. Jackson.