Yes, as of January 1st, 2018 you will need to be 609 certified with the EPA in order to purchase 1234yf refrigerant. The only exception is buying for wholesale or when purchasing containers that contain less than two pounds of refrigerant. This new rule applies to R-134a cylinders as well.

For R-22, R-410a, R-404a, MO99, R-422D, and other HVAC refrigerants you must have a 608 license.