First, and simplest solution is to have the cat spayed or neutered (I assume the latter, since you said "he.") However, if he is already neutered, it could be due to a more deep-seeded problem. Another possibility is that he has a urinary tract infection, or is otherwise sick. Therefore, I would recommend that you take him for a checkup and discuss the problem with your vet.

In some cases, the cat may be reacting to a change in the household. For example, cats will sometimes decide to start marking their territory when a new cat or kitten has entered the house, or if the normal household routine has changed significantly - i.e. a new person moving in, a baby being welcomed to the family, a significant change in their owner's routine, etc.

As you may or may not already know, cats are different than dogs when it comes to punishment. Basically, you need to catch a cat in the act of doing something bad, and then act right at that moment.

I have had issues with cats deciding not to use a litter box and I would recommend some, or all of the following:
1. Get a new litter box - sometimes a larger, different shaped or covered one will help
2. Change the litter box more often
3. If the cat is urinating in the same spots repeatedly, limit his access to these spots by closing doors, etc.
4. Get a few litter boxes and place them where the cat is urinating, thereby "forcing" him to use the box
5. Try to pay more attention to the cat. In some cases, he may be "punishing" you because you are not spending enough time with him

These are some guide on how to effectively train your cat to use the litter box:

1. If your cat is avoiding the litter box, one probable reason is that he may dislike the type of litter you are using in the litter box. Generally, cats like clumping litter that is non-perfumed so try switching to a natural cat litter which is green and biodegradable, provides better odor control, free of dust and feel's soft on their paws.

2. Another reason he is avoiding the litter box is that he has encountered territorialism if there are other cats in the household. Or your cat may be having some physical problem like painful urination, difficulty passing stools, and more. He may associate pain with the litter box, so try adding another litter box to help prevent fighting, have your cat checked thoroughly by a veterinarian to rule out any physical problems and train her again and gradually re-introduce your cat to the litter box.

3. Cats need privacy so avoid placing your litter box in the middle of the living room or areas where there are high traffic. Choose a low-traffic, low-noise location in your house which will make them feel secure and secluded.

4. Be sure that your litter box is clean. Be sure to clean the litter box twice a day.

5.

The first step is to know why your cat is urinating outside the box.

If you have a well train cat, there are different reasons that can cause your cat urinate outside the little box.

1-Medical problems
- Urinary tract infection. UTI causes painful urination. Your cat will associate the litter box with the pain, and he will start peeing in different spots in the house.

- Diabetes is a medical problem that causes excessive urination.

2-The litter box is dirty

3-Replacing the old litter box for a new different one. If you have bought a new litter box, your cat will need some time to get use to it.

4-Your cat does not like the location of the litter box

5-Your cat does not know where the litter box

6-Your cat is spraying. Male cat spraying or marking may be triggered by a number of reasons: mating season, stress or different changes in the cat's life. Spraying is not a litter box problem. Your cat is marking its territory, leaving a message for other cats.

7-Stress and anxiety

Cats suffer from stress when they have changes in their life. Stress can cause your cat peeing outside the litter box. A cat can develop stress due to:

1. Travel
2. A new family member, human or animal
3. Visitors
4. Injuries or other medical conditions
5. A new cat in the neighborhood
6. Moving to a new house
7. Changes in diet or daily routine
8. Absence of a family member
9. Noise
10. Illness

8-More than one cat sharing the same litter box