FN25.   Although the regulation states that a contractor may elect to verify all employees hired after November 6, 1986 and shall initiate verification of all such existing employees “within 180 calendar days of (i) Enrollment in the E-Verify Program; or (ii) Notification to E-Verify Operations of the Contractor’s decision to exercise this option…” (48 C.F.R. 52.222-54(b)(4)), the October 21, 2009 Supplemental Guide for Federal Contractors (“Supplemental Guide”) suggests that the choice must be made at enrollment: “NOTE: If you choose to verify your entire existing workforce in E-Verify, you must verify all of your existing employees except those that are exempt . . .. Once you decide either to verify the entire workforce or to verify only those employees assigned to a contract with the FAR E-Verify clause, you are not permitted to change that decision.” USCIS, E-Verify Supplemental Guide for Federal Contractors (M-574A) 16 (Oct. 21, 2009) (emphasis added).  The Supplemental Guide can be found at this link.  Various groups are seeking clarification and/or modification of this guidance as it is not only inconsistent with the regulations, but it is inconsistent with the rationale underlying the 180 day option—to allow contractors that find it difficult to identify those assigned to the contract the option of querying the entire workforce.