Starting Jan.1, 2020 in aircraft that fly in the U.S. under IFR and where transponders are currently required, namely class A, B and C airspace ADS-B out equipment must be operational.
European Safety Standards for Private Operators
Operators must develop and implement safety management systems and perform other steps required to bring their aircraft and operations to a level of compliance. The new European rules for larger turbine airplanes and helicopters will affect all private operations and is now required for compliance.