Medical
Have you taken your cat to the vet and checked for a urinary tract infection or similar? Also pain can lead to stress so have your cat thoroughly checked out by your vet. This is an important starting point! How big are the puddles your cat makes? This can often indicate if it is behavioural or medical.
Behavioural causes and patterns
Does your cat have other behaviours that concern you? E.g. Night time activity/restlessness? Is there any pattern to the accidents? E.g.overnight, on rainy days, when you work late? Certain days in the week? After visitors? How often does it happen, daily/weekly?
Other cats/animals
How many other animals do you have? How much time does this cat spend with each of them? Do they get on with anyone? How many other animals is this cat exposed to (i.e. neighbours)? If you have other animals, how much time does this cat spend where they can’t be disturbed by any of them?
Environment and location specifics
Is your cat an inside and/or outside cat? Does your cat urinate on vertical surfaces? Or at doorways or windows? Describe the places they defecate outside the tray? I.e. behind the couch Where is the food and water? What do you feed the cat? How often?
Litter tray specifics
Where are the tray/s?
Do they use the tray at all?
What kind of litter is in the tray?
How often do you replace the litter completely?
What are the dimensions of the tray and is it covered? Is it self-cleaning?
How often do you clean it?
What do you clean it with?
What do you use to clean up his accidents?
Other questions
Does your cat play with toys? If yes, how often and with what? How long for? Who stops playing first?
Lastly, what have you tried already to fix the problem?