25 C.F.R. § 171.535 – Why is BIA collecting this information from me?

(a) As part of doing business with you, we must collect enough information from you to properly bill and service your account.
(b) We are required to collect your taxpayer identifying number under the authority of, and as prescribed in, the Debt Collection Improvement Act of 1996, Public Law 104-134 (110 Stat. 1321-364).