That's mostly fixed the problem (occassionally when we're home another cat uses her litter box, so we also switched to cat genies, a type of automated box, so she has a fresh box that's hers and we don't have to clean that box immediately if another cat uses it). If it does, treating the problem will probably result in it using the litter box again (though it might take several days even after the problem is gone).Aside from urinary tract problems cats will pee outside if they are stressed out, marking territory (as in having a dispute with some other animal in the house), or if they smell urine already there. This is very difficult especially if the surface they peed on is porous. If so that is a good way to prevent it from revisiting the area in case there is some faint odor lingering (cats have a sense of smell that is much stronger than ours).Since then, he's started urinating all over in the basement.In the 8 years I've had him, he's never not used the litter box. If you aren't able to identify any changes (there's been a change, but sometimes it's hard to find), then start laying out litter boxes.We tried her on prozac, but that didn't help the litter box situation.Eventually, we set up her own litter box in the master bathroom, moved her food and water bowls to the bedroom, and made that her territory.If you don't get rid of the smell, the cat will continue to associate that spot as a place to urinate.
When it is a urinary tract problem a vet visit with treatment usually fixes the problem fast.
The behavioral squabbles over territory / smelling old spots is harder to deal with especially on carpeted areas... I won't repeat the information about having the vet verify that your cat is okay, but I would like to add some new information.
If the problem seems as though there's no solution, try adding another liter box to your home.
The universal rule of thumb tends to be While some single home cats can run flawlessly on one litter box, some cats need options.
On a personal note, my family has two dogs and one cat indoors.