My 12 yr. old yellow lab started urinating in the house in the same spot while we are at work. We take him out before we go to work, when we come home from work and before we go to bed. If he has to go in the middle of the night we take him out. Last night he didn't wake us up to go out he went in the same spot he urinated before. What is going on.

12 years is getting old for a lab, have you had him checked out by a vet?
Perhaps he is sleeping in that spot while you are away and urinating in his sleep?
Incontinence is a common problem in older dogs and one that can be managed.