Rule out medical problems with a veterinarian
Clean accidents with an enzymatic cleaner
Provide enough litter boxes
Keep litter boxes clean
Place litter boxes in quiet, accessible areas
Use unscented litter
Try different litter box styles
Reduce stress and household changes
Block access to previously soiled areas
Feed and play near problem areas
Spay or neuter the cat
Use pheromone diffusers
Increase daily play and enrichment
Separate cats if there is conflict
Avoid punishment
Consult a veterinarian or behaviorist if the problem continues