From the About Phoenix Mailroom: 90 Day Warning

I received the following email from Don:

Judy,
I plan on moving to Arizona next year with my girl friend. I've been told that if you already live together and move to Arizona that you are considered married after living in the state together for three months. Is this true?

Well, Don, there are probably quite a few cohabitating couples in Arizona who just got serious palpitations just from reading your question!

Arizona does not have common law marriage. That means that in Arizona, if you want to be married, you have to go through the marriage license/ceremony process. If you had a common law marriage that was recognized by one of the states that does provide for those legally, then it would be recognized in Arizona. Just a word to calm some fears; just living together does not make a common law marriage, even in those states that have common law marriages.

I can't quite imagine where a "90 day cohabitation = marriage" rule idea might have come from--was someone trying to scare you? ;-)