How old do kittens (male and female) have to be before they can be neutered?

You can neuter from 4 months, and spay (that's for females) from 5 months, but it is bst to do it around24-28 weeks old, which is around 6 months old. At that stage, the sexual organs are developed enough and the cat is big enough so the op is easy, but they will not have a chance to reproduce yet.

Silja (manager, Cats Protection Association ireland)

Thank you for your help silja.