Quasar has only voided inappropriately outside his trays on 3 occasions. He is 2 years old.
1) as a young kitten, the litter we were using had been changing from bag to bag and turned into a fine, heavy consistency. He peed outside the box. I changed the litter. He peed inside the box. Problem solved.
2) we were on a trip to Yellowstone NP and had been away from the hotel box for almost 11 hours. I offered him the travel box a few times, but he could not ever settle down to use it. We were on our way back to the hotel and he settled down on the floor of the back seat of our truck and started to pee on hubby's jacket. We stopped the truck quickly and let him out on his leash. After a long walk off the main road, Q was able to settle down and poop on hard, clear ground, behind a sagebrush. Poor guy.
3) after a foot surgery, I was unable to descend the stairs for about 5 days and, so, his favourite box was not getting scooped daily. The day I made it downstairs, I arrived in the room where his box is located to find him looking at me abashedly and peeing on the floor beside his box. His box was disgusting. I certainly could not fault him for that.
While camping or hiking, on a few occasions, Q has peed in sandy places. Not inappropriate voiding, but certainly outside the box!
The last occasion (#3) was almost 1 year ago. We have had no problems since. He has 3 boxes, 1 on every level of our home but usually uses the basement one. Every 3 or 4 weeks, I find a clump in one of the other boxes.