Originally, prisoners were denied the coronavirus stimulus money that was given out earlier this year (as part of the CARES Act).
However, on September 24, 2020, a judge in the Northern District of California issued an order certifying people incarcerated nationwide in state and federal prisons as a nationwide class, and said the federal government must stop withholding CARES Act payments to them. This includes an order to the IRS to reconsider all previous denials of such payments that were based on incarcerated status within 30 days.
Please note: claims must be filed before October 15, 2020 (according to the most recent information).
You can get more information on how prisoners can get their checks by visiting this website.