The election is made by paying the PTE tax timely.  Read the instructions for Form 120S. 

There are significant issues to know:

1.  I advise learning how overpayments and underpayments of the PTE are treated by the AZ DOR.

2. What happens when some shareholders opt out?

3.  Who are eligible shareholders?

Note that you have until the extended due date!  That is really nice. California requires shareholders to pay by March 15.  So Arizona law is more favorable.

I have only 1 Arizona client, so I have not yet learned all there is to know. The snip shows what I know.  Please share what you learn, if you have time.