6 U.S. Code § 969. Revalidation

The Secretary, acting through the Commissioner, shall develop and implement—
a revalidation process for Tier 2 and Tier 3 participants;
a framework based upon objective criteria for identifying participants for periodic revalidation not less frequently than once during each 4-year period following the initial validation; and
(3) an annual plan for revalidation that includes—
performance measures;
an assessment of the personnel needed to perform the revalidations; and
the number of participants that will be revalidated during the following year.