I don't need my ITIN any longer. How can I cancel it?

If you no longer need an ITIN, you don't need to do anything to cancel it or deregister with the ITIN.  The ITIN will expire automatically three years from the assignment date that appears on the IRS letter (CP565).

Keep in mind that many people only discover their ITIN has expired when they try to use it after a long period of inactivity. In such cases, the IRS will inform them that they must renew their ITIN or risk delays and increased taxes.

If you decide to inform the IRS that you no longer need your ITIN, you may send them a letter stating your intent. However, this is not a necessary step.  

Internal Revenue Service
ITIN Operation
Mail Stop 6090-AUSC
3651 S. Interregional, Hwy 35
Austin, TX 78741-0000

Remember that ITIN expiration is automatic, and the IRS does not have a specific procedure for deregistration.