The Internal Revenue Service plans to send expiration letters next week to tax practitioners who have not renewed their Preparer Tax Identification Numbers for 2014. 

The letters will be placed in PTIN holders’ online secure mailboxes within their PTIN accounts, the IRS said in an email to tax professionals Friday. Practitioners will be notified by email of the expiration and asked to check their mailboxes for more information. Letters will be mailed to practitioners who file by paper and do not have online accounts.

Even after a practitioner's PTIN has expired, he or she can still renew online or by paper, the IRS noted. The IRS will continue processing renewals throughout the year. 

To date, 554,000 practitioners have renewed 2013 PTINs for 2014, while 56,000 have registered for new PTINs for 2014.

For more information on renewing PTINs, click here.