If it's because you want to be sure people know he belongs to someone, should he get lost, you could have his ears tattoo'ed. Vets' do that in Denmark when cats are spayed/neutered and get their shots.

A few years ago, a friendly kitty showed up in our backyard, I checked his ears, called the vet and asked if he knew the cat. He did. So he gave me the phone no. to his owner and they came to get him.