Can we sell boxes of coffee a month past the date on clearance?

A customer stopped me to point out the coffee is "expired". I tried to tell him I'm not sure about our policy, but it's not really expired. Just passed the best by date.

That's probably why it's on clearance. I did reiterate I think not that I was sure. He got agitated and kept repeating it's expired like I didn't understand. Wouldn't leave til I took those boxes to back.