First of all, the only reason to put this in any bio is if a show has both union and non-union members in it.
It's a union requirement (...or at least it was for me a few years ago) to state that I was a member of Actors' Equity appearing in a "waiver" or "showcase" production. A lot of times, I've seen it indicated by an asterisk next to a performer's name, with a footnote somewhere saying "Member of Actors' Equity Association."
If you're on Broadway, or appearing in a union production anywhere in the U.S., there will always be a blurb in the program stating that the performers in the show are union members. In that case, it's not necessary or required that union members add in anything to their bios.
"Jaws is the Citizen Kane of movies."
blocked: logan2, Diamonds3, Hamilton22