26 U.S.C. § 6867 — Presumptions where owner of large amount of cash is not identified

(a) General rule If the individual who is in physical possession of cash in excess of $10,000 does not claim that cash—
(1) as his, or
(2) as belonging to another person whose identity the Secretary^* can readily ascertain and who acknowledges ownership of that cash, then, for purposes of sections 6851 and 6861, it must be presumed that that cash represents gross income of a single individual for the taxable year^* in which the possession occurs, and that the collection of tax will be jeopardized by delay.

(b) Rules for assessing In the case of any assessment resulting from the application of subsection (a)—
(1) the entire amount of the cash must be treated as taxable income for the taxable year in which the possession occurs,
(2) that income must be treated as taxable at the highest rate of tax specified in section 1, and
(3) except as provided in subsection (c), the possessor of the cash must be treated (solely about that cash) as the taxpayer^* for purposes of chapters 63 and 64 and section 7429(a)(1).

(c) Effect of later substitution of true owner If, after an assessment resulting from the application of subsection (a), that assessment is abated and replaced by an assessment against the owner of the cash, that later assessment must be treated for purposes of all laws relating to lien, levy^* and collection as relating back to the date of the original assessment.

(d) Definitions For purposes of this section—
(1) Cash the term “cash” includes any cash equivalent.
(2) Cash equivalent the term “cash equivalent” means—
(A) foreign currency,
(B) any bearer obligation, and
(C) any medium of exchange which—

(i) is of a type which has been frequently used in illegal activities, and (ii) is specified as a cash equivalent for purposes of this part in regulations prescribed by the Secretary.
(3) Value of cash equivalent Any cash equivalent must be taken into account—
(A) in the case of a bearer obligation, at its face amount, and
(B) in the case of any other cash equivalent, at its fair market value.

This section does not define the quoted term “cash”.