The tank may need perodic inspection in order to permit filling. So you mght need to add that to your question.

I do know the 20 pound propane tanks need a pressure test every so many years..

the tank is placed in a container covered with water. its then pressured to capacity.
if the container holding the tank has water spill out the tank is expanding too much and has failed inspection. at least this is my understanding of what was explained to me many years ago.....

of course the tank exploding etc is also a failure...