While cats can be more convenient than dogs since you don’t have to walk them all the time, they can be troublesome if they don’t want to use their litter boxes properly. In case your cat has trouble using a litter box, you might want to check out some possible solutions.
For example, many cats prefer fine grained litter rather than coarser litter. The location of your litter boxes can also make a difference along with having enough litter boxes for all of your cats. Then again, most cats would prefer to do their business everywhere in the house and let you clean it up without complaining, so that might be the best solution of all (from the cat’s point of view).