Ms. or Dr. will do just fine
The large, chain supermarket I go to has instituted a new policy: cashiers are supposed to address customers by name. So what happens? Each time I go, the person at the register looks for my last name on my credit card, looks at me, and then guesses whether to go for "Miss" or "Mrs.". One time I asked a cashier why she had selected "Miss." "Oh," she said, "that’s an all-purpose title, for when we don’t know if you’re married or not."
Wrong.
My sister put "PhD" on her credit cards for a while, but reports that it just got her dirty looks.

In Britain–or at Cambridge at least–they’re much more assiduous about the Ms./Mrs. distinction (or at least they were 15 years ago). At the time I was very much a Miss so I couldn’t take offense at it.
Comment by Kristin — May 17, 2006 @ 3:58 am