List 4 reasons a cat may refuse to use its litter box.

Too few litter boxes; Inappropriately positioned boxes (damp cellar, high traffic area); Inconvenient location (basement, second level); Hooded box (most cats dislike hoods); Box too dirty (not scooped/cleaned often enough); Box too clean (cleaned with harsh smelling chemicals, such as bleach); Liners (some cats are intimidated by plastic liners); Plastic underlay (convenient for the owner but not always accepted by the cat); Wrong type of litter (crystals or pellets); Litter not deep enough; Animosity between cats in the house (competition/guarding); or Difficulty getting into/out of the box, especially in elderly, arthritic cats