Hint: for more on related topics, see
There is proper litter box etiquette and a correct way to set-up your cat’s litter box. This affects the mannerism in which your cat relates to this territory. If your cat isn’t going in the litter box, It's time to take a closer look at their current litter box situation. Here are some basic rules.
One litter box plus one extra box for each cat. Your cat should have more than one place to do his/her business. Make sure the litter boxes are placed in different areas of your home.
Place litter boxes in separate, socially important areas. Litter boxes should not be in a dark corner in the basement, garage, or hidden. If your cat is marking outside the litter box, it’s important to put the boxes places where they’re marking. Litter boxes should be placed in areas where your cat spends the majority of their time (If your cat loves to hang-out in the living room, then that's where one of the litter boxes should be). Keeping litter boxes out in the open might not be your ideal scenario, but it’s ideal for your cat, and it can solve litter box issues. If you have multiple cats, do not place the boxes side-by-side, right next to each other.
Your litter box should have multiple exits. Cats need an escape route, they don’t like to feel cornered-in. If you have multiple animals in your home, and they’re approached while in the litter box, they don’t have a way out. One bad litter box experience can cause a cat to abandon it. If your only litter box is a deep box with one entrance, at least add a shallower one with multiple exits and/or an open pan (no lid) to your cat’s repertoire, and eventually try to replace them.