Ensure the cat is comfortable. If an animal shits in the corners because it does not like the tray, replace the capacity. Usually the pan is too small, it often requires two tanks – cats are very clean. Perhaps next to the tray there was an unpleasant cat smell air fresheners, cleaning supplies you clean carpets or furniture, etc.
Try to "scare" the cat from corners. You can try to kill the smell from cat marks by treating the surface with a special solution (available at pet stores) or improvised means (vinegar, detergent, mustard, iodine, etc.). Put in the corners or move furniture, that is, make this place inaccessible to cats. You can put her food bowl – cats do not crap where you eat. This method has two drawbacks – the smell may become stronger if the cat will continue to spoil, and can just move to another place, having chosen the next area.
Sterilize the animal. Hormonal medications or surgical sterilization will help to eliminate any physical problems, and the cat will become calmer. If the cat marks the corners, attracting suitors, it is the only effective solution.
Try to train the cat. Praise the pet every time it will visit the tray. Put the tray in the corner or lay down the newspaper, gradually move the "toilet" further from where she squatted. "Mark" territory with his dirty things (socks, sweaty t-shirt), carefully rubbing the fabric on the surface the cat needs to recognize your primacy in the house.
Show the cat the vet. That cat shit can be a symptom of diseases of the kidneys or bladder. To exclude pathology, the examination and get expert advice. You may need to change the feed and treat the animal, then the problem will stop.
Glue the corners. To discourage cats desire to get closer to the corners, stick on the floor with strips of double sided tape. Cats don't like dirty feet, and even adhered to the floor of the limb can lead her into a panic. Stressing out, stop cat fouling in the corners.