The IRS has sent PTIN holders a notice and has posted on its website updated renewal rules for PTINs. Your PTIN will now expire on a calendar-year basis, so if you obtained or renewed your PTIN between September 28, 2010 and the present, it will expire on December 31, 2011. Therefore, your PTIN number will expire at the end of the calendar year rather than one year after you acquired it.
Here are the IRS FAQs on PTIN expiration:
PTIN renewal is expected to be available in October 2011. Check www.irs.gov/ptin for updates.
PTINs now expire on a calendar year basis. If you obtained or renewed your PTIN for the 2011 filing season (e.g., between September 28, 2010 - present), your PTIN expires on 12/31/2011.