It depends on where they are doing time, what their charges and criminal history are. The federal system has a program called RDAP that can reduce a sentence by twelve months. Some state systems have reductions for work credits. All places have good time credits for inmates that have no incident reports.
https://www.inmateaid.com/ask-the-inmate/is-it-possible-for-and-inmate-to-get-a-sentence-reduction#answer
Accepted Answer Date Created: September 14,2014