Very often, my cat peeing outside of the litter box is associated with bladder problems. Cystitis, kidney inflammation, and urolithiasis make the process painful, and the cat associates discomfort with the litter box. As a result, the cat is peeing outside the litter box because it is afraid of experiencing pain again.
If you notice blood in the urine, frequent visits to the litter box or plaintive meowing, urgently contact your veterinarian.