from https://www.humanesociety.org/resources/preventing-litter-box-problems

Cats can be finicky about their bathroom habits, so unless you want to be dealing with a regular mess at home, keeping your cat's litter box up to their standards is very important. The following suggestions should keep your cat from "thinking outside the box."

Boxes & litter

How many?

The general rule of paw is one litter box for each cat in the home, plus one more. That way none of them will ever be prevented from eliminating in the litter box because it's already occupied.

Litter Box Items on Amazon.com

It's not possible to designate a personal litter box for each cat in your household, as cats may use any litter box that's available. That means a cat may occasionally refuse to use a litter box after another cat has been in it. In this case, you'll need to keep all of the litter boxes extremely clean, and you might even need to add additional boxes. However, it's best not to place all the boxes in one location because your cats will think of them as one big box and ambushing another cat will still be possible.

Covered boxes

Some people prefer to provide their cats with a covered litter box. While covered boxes can increase privacy and decrease the amount of litter that flies from the box when your cat buries their business, there are some potential downsides. An “out of sight, out of mind” little box is easy to forget about, which may lead to a dirty box with odors trapped inside (which is even less likely to be appealing to your cat). Covered boxes can also be difficult for larger cats to turn around and position themselves in, and may lead to easier ambushes upon exit.

Ultimately, if your cat doesn't like a covered box, they won't use it. To find out which type your cat prefers, you may want to experiment by offering both types at first.

Self-cleaning boxes

There are a wide variety of litter boxes available that offer convenience and automation in cleaning your cat’s litter. Buyers beware: some of these features may prevent a cat from wanting to use their litter box, so if your cat is used to a traditional box, it’s best to stick to what they know.

Pick of the litter

There are several different types of cat litter on the market. The most popular ones are traditional clay litter, scooping/clumping litter, crystal-based/silica gel litter and plant-derived/biodegradable litter.

Most cats prefer fine-grained litters, presumably because they have a softer feel. Newer scoopable and “clumping” litter have finer grains than typical clay litter and are very popular because they keep down the odor. But high-quality, dust-free clay litters are fairly small-grained and may be perfectly acceptable to your cat.

Once you find a litter your cat likes, stick with it. Switching litters constantly could result in your cat not using the litter box.

If your cat has previously been an outdoor cat and prefers dirt, you can keep them out of your houseplants by placing medium-sized rocks on top of the soil in the pots. You can also mix some soil with their regular litter to lure them in. A cat who rejects all types of commercial litters may be quite happy with sand.

Many people use scented litter or air freshener to mask litter box odors, but often times, these odors can be offputting to cats. A thin layer of baking soda placed on the bottom of the box will help absorb odors without repelling your cat.

Set up

Most people tend to place the litter box in an out-of-the-way spot to minimize odor and prevent cat litter from being tracked throughout the house. But if the litter box ends up in the basement next to a creepy appliance or on a cold cement floor, your cat may be less than pleased, so you may have to compromise.

 - Keep the litter box in a spot that gives your cat some privacy but is also convenient. If the box is too hard to get to, especially for a kitten or an elderly cat, they just may not use it.

 - Avoid placing litter boxes next to noisy or heat-radiating appliances, like the furnace or the washing machine. Noises can make a cat nervous, while heat from a dryer or furnace can magnify the litter box smell, which could make them stay away from the litter box.

 - Put the box far away from their food and water bowls. Place at least one litter box on each level of your house. That way your cat has options if access to their primary box is blocked (the basement door is closed or your dinner party has them holed up in the bedroom.) If you have more than one cat, provide litter boxes in several locations so that one cat can't ambush another cat using the litter box.

 - If you keep the litter box in a closet or a bathroom, be sure the door is wedged open from both sides to prevent your cat from being trapped inside or locked out. Depending on the location, you might consider cutting a hole in a closet door and adding a pet door.

Cleaning

To meet the needs of the most discriminating cat, you should scoop feces out of the litter box daily. How often you actually replace the litter depends on the number of cats you have, the number of litter boxes and the type of litter you use.

Twice a week is a general guideline for replacing clay litter, but depending on your circumstances, you may need to replace it every other day or only once a week. If you clean the litter box daily, you might only need to change clumping litter every two to three weeks. If you notice an odor or if much of the litter is wet or clumped, it's time for a change. Scrub the box every time you change the litter. Use mild dish detergent to clean it, as products with ammonia or citrus oils can turn a cat off, and some cleaning products are toxic to cats.

Liner notes

Box liners are strictly a convenience for the owner; supposedly, the liner can be gathered together and tied just like a garbage bag, but the truth is that most cats shred it to bits while scratching in the box. However, it might work if your cat doesn't work too hard to bury their waste.

Depth of litter

Most cats won't use litter that's more than about two inches deep. In fact, some long-haired cats actually prefer less litter and a smooth, slick surface, such as the bottom of the box. Adding extra litter won’t reduce the amount of cleaning necessary for a litter box.

Training

There's really no such thing as "litter training" a cat in the same way one would housetrain a dog. You actually don't need to teach your cat what to do with a litter box; instinct will generally take over. You do need to provide an acceptable, accessible litter box, using the suggestions above.

It's not necessary to take your cat to the litter box and move their paws back and forth in the litter. If you move to a new place, however, you will need to show your cat where the box is.

If problems begin

If your cat begins to go to the bathroom outside the litter box, your first call should always be to your veterinarian. Many medical conditions can cause a change in a cat's litter box habits. If your veterinarian examines your cat and gives them a clean bill of health, your cat may have a behavior problem that needs to be solved. Punishment is not the answer, nor is banishing your cat outdoors. For long-standing or complex situations, contact an animal-behavior specialist who has experience working with cats.

Adapted from material originally developed by applied animal behaviorists at the Dumb Friends League, Denver, Colorado. All rights reserved."