As of September 2014, reactivating a Yahoo! account involves signing into the account, confirming the Yahoo! ID, filling in CAPTCHA verifications and selecting "Reactivate" on the screen. It may take up to 24 hours to reactivate the account, and emails may be deleted and unrecoverable. Any lost data during the time the account was inactive may not be recovered, such as contact information and preferences.
Recovering an account is not possible if the user violates the terms of service or the account does not have a login for 12 months. Violations of the terms of service include, but are not limited to, nonpayment of fees for certain Yahoo! services; exploiting proprietary programming of Yahoo!; and breaking state, federal and local laws.
Other violations of the terms include intending to harm minors; uploading harmful content that is hateful, incriminating and libelous; falsely representing someone else; transmitting copyrighted material; interfering with Yahoo! servers; and stalking someone. These terms of service were updated March 16, 2012.
Sometimes, a third party deletes a Yahoo! account without any violations of terms of service or lack of login. If this is the case, Yahoo! recommends changing the password on the account to prevent a third party from closing the account permanently or using Yahoo! services illegally.