The number of registered voters in Shelby County changes every business day, as people register, or move out of the county.
Reports are run periodically. There is a column for active voters, one for inactive voters, and a total by precinct split. The .xlsx version contains tabs with pivot tables that detail registration in various districts. Current reports may be found using the links below.
February 1, 2020 Active and Inactive Voters by Precinct Split
Tennessee requires the Shelby County Election commission to run a report each six months listing the source of voter registration applications. This report also details the number of additions and cancellations for each precinct. Those reports can be accessed here.
Trent Cobb at the 2017 National Voter Registration Day Event.