Instructions
Place a second litter box in the new location, while leaving the first litter box in its original spot. Even though you may be inclined to simply move the original litter box to a new location, don't do it.
Introduce your cat to the second litter box. This can be done by carrying your cat to the new area and allowing her to sniff around and get used to the idea of having her bathroom relocated.
Move the first box, slowly. Every day move the original litter box a few feet closer to the one in the new location. This may sound like a time-consuming nuisance, but if you want your cat to get used to the idea while avoiding any negative behaviors, don't rush her.
Allow your cat to use both litter boxes for a few days once the original box has strategically made its way to where the second box has been placed. By allowing your cat to use both boxes in the same location, you will be helping to familiarize her with the area, which will make the final step a breeze.
Remove the original box from its current location, leaving behind the new box. At this point your cat should be fully transitioned and used to her new location. It may have seemed like an eternity, but the whole process should really only have taken approximately two weeks.
Place a piece of furniture or some other obstacle in the exact location of the original litter box. This will act as a deterrent, reminding your cat that her box is now in its new location.
How to Move a Litter Box
The thought of moving your cat's litter box may seem like no big deal to you, but to your cat, it can be a huge deal. Cats are creatures of habit, like everything in its place and do not often cope well with transition, especially when it comes to where they relieve themselves. A sudden change in the placement of a cat's litter box can result in spraying and urinating in areas that are unacceptable. For this reason, moving the litter box should not be done with haste.