You don't have to. There's no law that says that you need to and there's no registration fees like many counties and cities have for your intact rat like they do for dogs. But neutered rats can live longer and be healthier and it's best if you have females.
It is a good idea to neuter your pet rat to prevent certain prostrate cancers and unwanted baby rats if you have a pair. Males might also be more aggressive if unneutered.
