Two inches of litter in the box seems to be the norm. Cats tend to like to dig all the way to the bottom of the box, dragging the litter up and over the waste. A deeper level of litter will make it too hard for your cat to reach the bottom of the box. Too little litter, and the cat will have to dig and scratch in too many locations in the litterbox, causing him to give up in frustration and decide that next time he ll just go behind the couch. Clean the litterbox at least once daily.
Cats dislike trying to cover up their latest addition while having to evade past deposits.
This is especially true in multicat households. Their own is bad enough, but cats will draw the line at having to dig through a housemate s deposits in order to do their business. Some cats are so picky that if they ve urinated in the box just once, they consider it too dirty to use again, which leads to defecation in inappropriate places. The most common seems to be the bathtub. The logical explanation for this seems to be that the bathtub is cleaned immediately upon discovery of the gift , and the cat can count on that area always being clean and fresh enough for his easily offended sensibilities.