How to Close an Apple ID
As of 2011, Apple does not allow users to close or cancel an Apple ID. However, you can change your password, credit card information, your Apple ID and any devices connected to your Apple ID. While these changes will not close an Apple ID account, they do accomplish the same objective. These changes will prevent individuals with current information about your Apple ID account from using the account to make unauthorized purchases.
Remove the credit card information linked to the Apple ID. According to Apple, you can change the credit card information linked to your Apple ID by going to My Apple ID, and selecting "Manage Your Account." You will see a field to change or remove your credit card information.
Change your Apple ID. Changing your Apple ID will make your old username and password inactive, and you can replace your old Apple ID with a new Apple ID. Similar to removing credit card information, to change an Apple ID visit My Apple ID and go to "Manage Your Account." You will be able to edit an Apple ID after you enter your current Apple ID and password. However, according to Apple, you cannot change a MobileMe and iChat Apple ID.
Reset your Apple ID password so that no one who currently has knowledge of your Apple ID will be able to access the account. As above, you can reset your password using the Manage Your Account feature on My Apple ID.
Deauthorize your Apple ID account on all devices linked to the account. This may include multiple computers, an iPod and an iPhone. For example, you can deauthorize a computer by viewing the Store Tab on iTunes and selecting deauthorize this computer.