Cats may periodically refuse to use their litter box. Below are 5 common causes of litter box refusal that can be corrected.

• Cleanliness. Or rather a lack of it. Cats are very clean creatures and they can be very fussy when it comes to a dirty litter box. Waste should be removed from the litter box on a daily basis, and the litter replaced each week. You should also periodically clean the litter box using warm water, mild soap and a thorough rinsing. Do not use ammonia as cats have an aversion to it.
• Illness. One of the most frequently seen symptoms of FUS, or Feline Urinary Syndrome, is a refusal to use the litter box. This can be a very serious illness so be sure to contact your veterinarian if you suspect that your cat has FUS.
• Overcrowding. Cats can be territorial and some may refuse to use a litter box that's also used by another cat. As a general rule of thumb you should have no more than two cats per litter box, though you may need to get one for each if necessary.
• Pick of the Litter. Many cats have preferences when it comes to the type of litter you use. Some prefer a conventional clay-type filler. When changing litters, do so slowly by mixing in a little bit of the new filler with the old and gradually increasing it.
• Privacy. Just as you like some privacy when going to the bathroom, so do many cats. Give your cat her privacy by keeping her litter box out of high-traffic areas.