My 17 year old cat, Annie, had started to pee outside the litter box every single night. During the day, there was never an issue - but each morning, I would come down to find a puddle of pee right in front of the box. The set up that we have is a large tupperware tub set underneath a shelf - it has a large opening cut into it that she has to step into. We did this because with the flat boxes, she was half stepping in and would miss the box.
So, at first we enlarged the hole thinking that maybe she was having trouble stepping in, but the problem persisted. We made sure that the box was cleaned religiously every morning, afternoon after work and before bedtime thinking that maybe she was getting more fastidious.. same issue. We put pee pads in front of the box hoping that she would go there instead of on the tile, she missed the pee pads... So my husband jokingly said, maybe she can't see.
Ding ding ding!!!!! Her night vision is failing. We put a nightlight out that illuminates the box and the problem is solved. No more peeing outside the box at night!!! Hoping this can help someone else
I had to put him down in October and miss him terribly.