I would have to agree with the other comments. Most likely, the cause may be due to a change in the kitty litter. If that isn't the case, then perhaps your cat has a weakened bladder.
If the litter isn't clean enough, then that's also another issue. One of my cats does this every now and then (I use silica litter, it absorbs the urine in the crystals) and because their sense of smell is so high, then I know it's a sign to get the litter completely changed.
Good luck!
Have you changed your kitty litter to a different brand? This happened to my cat and we discovered she didn't like her new litter.
But PrettyKitty1 has raised some good possible answers.
Best of luck.
AH!! Maybe UTI?? Why don't you take him to the vet see if he has any bladder infection? UTI causes pain when urinating, causing the cat to associate pain with the box. Have you noticed if he cries when he pees?
You haven't changed the litter, have you? Also, is the box clean? Make sure you scoop the box clean. Is there a new arrival? Is he stressed? (Loud noise, moving). Are you stressed? Has anything changed in the house? If you're stressed he'll sense it and become stressed as well, depending on how strong the bond is. Have you adopted another pet? Also, make sure there are no other cats wondering around the house. He may be marking...even fixed cats mark when they feel threatened by the presence of another cat.
I hope you find a way out of this mess. I know how you feel. One day my cat urinated in my brand new couch which I haven't even finished paying for. It hurt lol. The cause was litter change. I switched to feline pine. He didn't like it and went on my couch. I had to go back to Fresh Step. I could tell he had been holding it all night long, that poor thing didn't want to mess my couch but cats are fastidious creatures of habit.