If you decide to transfer your domain, your new provider will usually ask you for an authorization code, a unique 6- to 32-character code designed to prevent fraudulent or unauthorized transfers. This code is an extra safety feature — similar to a credit card verification code or PIN for your domain — that helps ensure that the customer transferring the domain is indeed the owner of that domain.
You can find the authorization code for a domain registered with Yahoo! on your Domain Control Panel. Learn how to find your authorization code.