42 U.S. Code § 3543 - Preventing fraud and abuse in Department of Housing and Urban Development programs
(a) Disclosure of social security account number
As a condition of initial or continuing eligibility for participation in any program of the Department of Housing and Urban Development involving loans, grants, interest or rental assistance of any kind, or mortgage or loan insurance, and to ensure that the level of benefits provided under such programs is proper, the Secretary of Housing and Urban Development may require that an applicant or participant (including members of the household of an applicant or participant) disclose his or her social security account number or employer identification number to the Secretary.
For purposes of this section, the terms “applicant” and “participant” shall have such meanings as the Secretary of Housing and Urban Development by regulation shall prescribe. Such terms shall not include persons whose involvement is only in their official capacity, such as State or local government officials or officers of lending institutions.