common law marriage

My partner and I have been together for 17 years. We have lived in Utah for two of those. We are not legally married. Do we need to file state and federal taxes as single or married? Utah is a common law marriage state.

If my partner and I live together long enough, won't we have a common law marriage?
Contrary to popular belief, even if two people live together for a certain number of years, if they don't intend to be married and present themselves to others as a married couple, there is no common law marriage. More particularly, a common law marriage can occur only when:
a heterosexual couple lives together in a state that recognizes common law marriages
for a significant period of time (not defined in any state)
holding themselves out as a married couple -- typically this means using the same last name, referring to the other as "my husband" or "my wife" and filing a joint tax return, and
intending to be married.
Unless all four are true, there is no common law marriage. When a common law marriage exists, the couple must go through a formal divorce to end the relationship.
Which states recognize common law.
I copied this from "NOLO'S LEGAL ENCYLOPEDIA" NOLO.COM