Hi, is there a rug or something he is using near the box? I've had this exact problem with 2 older cats, they had never had a problem with it before. For one there was nothing we could do, he just refused to go #2 in his box, we tried everything, the other cat was going on a rug near her box and once we removed it she was back to using her box for everything. I'd say just keep the boxes clean and remove anything he may like on the floor. One theory I heard was that as they get older the digging in the box is harder on their little feet. You can try getting a box for him and putting pee pads for puppies in it instead of litter.