You need to wait until you are no longer feeling the effects from the benzos. For benzos with a short half-life, 8-12 hours is fine.
I just wanted to mention that I have definitely had Xanax affect my intoxication when I drank at night even when I had taken the Xanax in the morning, so I would say to wait until the next day to drink even of you are no longer feeling the Xanax. My friend had the same experience, where he had taken a Xanax in the morning and figured he would be fine to drink at night, but ended up blacking out after drinking an amount of beer that definitely would not have caused any amnesia on its own.
Still closed.