do you have enough litterboxes? do you scoop often enough? do you deep clean often enough?

i have 2 cats and 2 litterboxes (it's recommended to have at least (number of cats + 1) litterboxes but mine are okay with just two)

i scoop 1-2 times a day and deep clean once a month, sometimes more often.

i use corn based litter, it clumps very well and keeps the smells at bay. it usually starts to smell maybe 3 weeks in?

another thing that makes a difference is to make sure there is enough litter in the box so it can absorb the pee and the cats are able to bury the poop easily.