In Washington anyone who serves, mixes, sells or supervises alcohol for drinking on the premises holds a MAST permit, within 60 days of being hired. Class 12 is for 21 and over and may mix and pour; Class 13 is for 18 to 20 and may serve but not mix or pour. A permit lasts five years, is not renewed - a new class is taken before it runs out - and has no grace period after. It belongs to the person.
Serving on the floor needs a permit in force that day, or the first 60 days. Behind the bar, mixing and pouring, needs a Class 12.