Your domain name belongs to you until your registration expires, even if you cancel your plan. Yahoo! does not own your domain name.
If you registered your domain through Yahoo!, and you decide to cancel your plan:
If you used a domain you previously owned with your Yahoo! plan, and you decide to cancel:
Important: Before You Cancel
If you decide to cancel, we'll ask you a few questions to help you decide how to manage your domain name after you cancel your Yahoo! service. We strongly recommend that you make arrangements for your domain name before you complete the cancellation process.
If you intend to keep your domain name after you cancel, consider signing up for our basic Yahoo! Domains plan, which will allow you to continue managing your own domain with your Yahoo! tools — even if you'd like to associate your domain with another web hosting service. You can also transfer your domain to another provider.
If you choose not to renew your domain name when it expires, someone else may be able to buy it!