Section 162.610 - Implementation specifications for covered entities(a) The standard unique employer identifier of an employer of a particular employee is the EIN that appears on that employee's IRS Form W-2, Wage and Tax Statement, from the employer.(b) A covered entity must use the standard unique employer identifier (EIN) of the appropriate employer in standard transactions that require an employer identifier to identify a person or entity as an employer, including where situationally required.(c) Required and permitted uses for the Employer Identifier.(1) The Employer Identifier must be used as stated in § 162.610(b) .(2) The Employer Identifier may be used for any other lawful purpose. 67 FR 38020 , May 31, 2002, as amended at 69 FR 3469 , Jan. 23, 2004