What is the difference between a registered chihuahua and an unregistered chihuahua?

Registration papers are only important if you want to breed or show the Chihuahua. They don't really prove that the dog is purebred..But if the dog is registered, AKC can send you a family tree to help you know all of the dog's ancestry..That is very helpful for a serious breeder..
My spouse's aunt registered many un-purebred dogs, so there are about 100 falsely registered Chihuahuas out there from her bloodlines alone.( 30 years ago) ..plus the offspring of those through many generations..

A couple hundred dollars. =)

document difference.

The difference is the papers...AKC registered papers. The papers are documentation that they're purebred and shows their bloodline. Only important if you plan on breeding or want bragging material or to pay a lot more money for the animal.

It is simple...registered animals of whatever species are purebred animals which come with papers and traceable ancestry. Unregistered animals are just reportedly purebred and you must just go on the word of the breeder. Registered animals are typically 2-3X the price of unregistered animals

As others have said, the only difference is that one comes with registration papers and one doesn't. Don't be fooled that AKC registration (or any other breed registry) automatically equals quality. It doesn't. It only means that the dogs parents were purebred. Many people are very easily tricked into thinking that just because they bought a registered dog they got a very high quality dog. While, registration is a step in the right direction, it's not everything. If all you're after is a pet, I would recommend looking at your local shelters for a chihuahua, it's a popular breed that often ends up in shelters. If there aren't any near you, try finding a chihuahua rescue group in your area.

Don't be fooled into spending hundreds of dollars at a pet store or in the paper for a dog advertised as 'high' quality because it comes with registration papers. You'll find what you're looking for for next to nothing at a shelter or breed rescue.

unregistered chihuahuas are the ones that sneak across the border. They are annoying, registered or not.

haha...one had to jump the fence to get here :)

An unregistered one could possibly have another breed of dog in the bloodline. To make sure he is pure bred you want papers. If a dog is papered he is worth way more money anyway.

Registered means you can breed with other registereds and then you can sell the offspring with papers available that they are full blooded.