The statutory anchor is INA section 203(b)(5), and the source-of-funds regulation is at 8 C.F.R. section 204.6(j)(3). The Reform and Integrity Act of 2022 added INA section 203(b)(5)(L), which codifies the kinds of source-of-funds documentation USCIS may require, including tax returns, bank records, judgment statements, and evidence of lawful acquisition. Section L expressly contemplates inheritance, gift, and loan as recognized lawful sources, but does not reduce the documentary burden when the source is inheritance rather than earned income.
USCIS adjudicator guidance lives in the Policy Manual at Volume 6, Part G. The seminal case on lawful source remains Matter of Soffici, 22 I&N Dec. 158 (Assoc. Comm'r 1998), which holds that the petitioner's capital must be the petitioner's own and that lawful acquisition must be traced. In practice, for inheritance, USCIS expects you to document both who the decedent was and how the decedent lawfully accumulated the assets that flowed to you, and then to trace those assets through the estate administration into your accounts and onward to the new commercial enterprise.
The federal courts in Battineni v. Mayorkas, Civ. No. 22-1332 (D.D.C. Oct. 2, 2024), and Zhou v. Noem, Civ. No. 19-2650 (D.D.C. Feb. 6, 2025), have held that the source-of-funds inquiry is "narrow" and that the petitioner is not required to trace every penny beyond the immediate source. These rulings are useful as legal argument in inheritance cases where the decedent's records are decades old or partly missing. They are not binding on USCIS adjudicators outside the parties to those cases, however, and practitioners report that USCIS has not changed its requesting behavior in response to either decision. The prudent posture is to over-document and to preserve the legal argument as a backstop.
For inherited assets that pass through a foreign legal system, USCIS has historically accepted opinions from a qualified foreign legal expert explaining the relevant succession law. That is particularly common in jurisdictions with intestate succession, forced heirship, or community-property regimes that do not match U.S. probate norms. Whether a foreign-expert opinion is sufficient on any particular record depends on the entire record and the discretion of the adjudicating officer.