25 C.F.R. § 20.602
How does the Bureau verify eligibility for social services?
(a) You, the applicant, are the primary source of information used to determine eligibility and need. If it is necessary to secure information such as medical records from other sources, you must authorize the release of information.
(b) You must immediately report to your social services worker any changes in circumstances that may affect your eligibility or the amount of financial assistance that you receive.