Each cat is different, so it may take a few days or a few weeks. Some may need a longer training period.
Start off with moving the litter box closer and closer to the toilet. Then have the litter box on top of a closed toilet (this obviously works better if you have an extra bathroom that you don’t use often.) Once your cat gets used to the litter box on top of the toilet, you’re ready to open the lid.
There are a few different options. You can purchase a kit to help you integrate your cat to using the toilet. Or you can use a mixing bowl. The kits are generally pretty easy to use.
If you opt for a bowl, turn off the water so the toilet bowl is empty. Place litter in the bowl. As your cat gets used to using the bowl, slowly reduce the amount of litter you use and start adding a little water to the bowl. When you’re pretty sure your cat has learning how to balance on the bowl. Remove it and turn the water back on.
At any point, if you notice your cat having trouble, go back a step- your cat wasn’t ready to move forward.
Regardless of whether you have a kitten or an older cat, it is possible to train your cat to use the toilet.
Be patient throughout the process, and reward your cat every time you see him using the toilet. You want your cat to associate using the toilet as a litter box as a good change.