National Statistics on Deadly Force Transparency Act of 2021 This bill establishes a framework to require law enforcement agencies to collect data on the use of deadly force by law enforcement officers. Specifically, it requires federal, state, and local law enforcement agencies to collect, compile, and submit to the Department of Justice's (DOJ's) Bureau of Justice Statistics data on the use of deadly force by law enforcement officers. DOJ must reduce by 10% the allocation of funds under the Edward Byrne Memorial Justice Assistance Grant Program for a state or local government that fails to substantially comply.