Tax return preparers who prepare all, or substantially all, of a federal tax return for compensation are subject to certain requirements including registration in the IRS Registration System.
The ID number provided will take the form of the Preparer Tax Identification Number (PTIN) which is mandatory for all paid preparers as of January 1, 2011. Preparers who already have a PTIN still need to register in the new system.
For 2018, the IRS is not charging a fee to obtain or renew a PTIN.