As a pet owner, there are few joys as great as the day you potty train your pet. With dogs, it's a lot of work. With cats, it's usually a lot easier. Cats are often more inclined to use their litter boxes. That's also why it can be so, so frustrating if, eventually, they stop.
If your cat is peeing or pooping outside of its litter box, you are no doubt looking for answers (that's probably why you're here in the first place, after all). Here are some reasons your cat might have starting doing his business outside of the litter box—because you can't start to correct the behavior until you know why it's happening in the first place.
Why did my cat suddenly start peeing or pooping outside the litter box?
If your cat was once a perfect litter box user and then suddenly changed his or her behavior, that's a signal that you should be looking for what changed in your cat's life. Maybe it's something obvious, like you just moved to a new house. Maybe it's something less obvious, like a new or developing medical condition. Whatever the cause, know that cats don't just start using the bathroom outside of their litter box for no reason, so this is a call to action for you as a pet owner.
Why older cats start peeing or pooping outside the litter box
Like humans, cats' bodies change as they age and sometimes that means that bodily functions that used to work perfectly start to work less perfectly. Middle aged and older cats, and larger breeds, are at an increased risk of developing urinary incontinence, or the lack of ability to control the bladder. If this is the case, your cat isn't going outside of the litter box on purpose, but because she can't hold it like she used to.
Obesity is the biggest risk factor associated with incontinence, so it's important to prioritize helping your cat maintain a healthy weight, especially as they get older. If your cat is getting on in years or if the accidents are small, but frequent (which would indicate urinary tract leakage), you should see your vet right away to diagnose the root cause of the incontinence.
You should also keep an eye on your elderly cat, especially if the accidents are happening really close to the litter box. Sometimes older cats develop physical limitations (think about older humans with arthritis) that can make it tough to get into top entry boxes and litter boxes with high sides. If this is the case, you might simply need to invest in a new kind of litter box that's easier for your aging cat to use.
Potential medical reasons your cat might be peeing or pooping outside of the litter box
Even young cats can struggle with using the litter box like they're supposed to if certain medical issues come into play. If your cat has started using the bathroom outside of the litter box, he might have a urinary tract infection, Feline Interstitial Cystitis, kidney stones or another blockage, according to the Best Friends Animal Society. If you think medical issues might be causing your cat's potty training regression, take them to the vet immediately for a proper diagnosis.
Other reasons cats start using the bathroom outside of the litter box
One of the most common reasons that a cat will stop using the litter box is one that is entirely within your control as a cat owner. Cats are very mindful of hygiene and cleanliness and they won't use a litter box that hasn't been cleaned as often as they'd like. If you've been skimping on cleaning the litter box, there's a very good chance that's the culprit in your cat's behavior change. If you have been cleaning it, try cleaning it even more frequently. It could be that your cat's cleanliness standards are just even higher than yours.
If you've just made a major life change—like moving, adopting a new pet, having a new baby, inviting a new S.O. or roommate to live with you (or breaking up with an S.O. or parting ways with an old roommate)—your cat has definitely noticed and that change could be stressing her out. Even changes that don't seem like they would affect the cat directly (like you being stressed out about a new job or in a bad mood because money is tight) can cause the cat stress. And, sadly, that stress can manifest in litter box regression.
If anxiety is the cause, Animal Planet suggests setting up the litter box in a quiet area with minimal household traffic, so your cat can have a calm space to do their business.
If you've just moved or invited a new cat into the house, your cat might start using the bathroom outside of the litter box as a form of marking, to make it known that the house is his territory. If your cat is engaging in marking, the urine will often show up on vertical surfaces (like walls and the sides of furniture), will appear in small amounts, and will likely smell especially strong. Sometimes, cats will even start marking if your neighbor gets a new cat and they can see it through the window.
To curb marking, the ASPCA recommends closing the blinds if your cat might be reacting to neighborhood cats, making sure that the cat in question is spayed or neutered, cleaning the marked areas up with an enzymatic cleanser designed to neutralize pet odors, using a synthetic cat pheromone in areas where the cat has marked, and finally consulting a vet about medications if the marking might be a result of anxiety. It's important not to react by rubbing your cat's nose in the urine, spanking the cat, or using an ammonia-based cleaner on the area.
They just don't like something about the litter box:
Cats are really finicky and they want things just right. If your cat isn't vibing with something about the litter box sitch, he'll just stop using it. The thing your cat doesn't like could be anything from the kind of litter you're using to the location of the litter box. If you've recently changed anything related to the litter box (or the room the litter box is in), that could definitely be the cause. If you haven't, it could be that your cat's tastes have changed and you're in for a lot of trial and error until you find a new combination that appeases Her Majesty.