Rule out medical causes with a veterinarian
Clean accidents immediately with an enzymatic cleaner
Remove all odor traces from the carpet
Add more litter boxes
Place litter boxes in quiet, accessible locations
Scoop litter boxes daily
Change litter regularly
Use unscented litter
Try a different litter type if needed
Use a larger, uncovered litter box
Keep litter boxes away from food and water
Reduce stress and household changes
Block access to soiled carpet areas
Use deterrents on carpeted spots
Provide more play and enrichment
Feed the cat near problem areas
Reward litter box use with treats
Consult a cat behaviorist if the problem continues