Sec. 6201 Assessment authority
(a) Authority of Secretary. The Secretary is authorized and required to make the inquiries, determinations, and assessments of all taxes (including interest, additional amounts, additions to the tax, and assessable penalties) imposed by this title, or accruing under any former internal revenue law, which have not been duly paid by stamp at the time and in the manner provided by law. Such authority shall extend to and include the following:
(1) Taxes shown on return. The Secretary shall assess all taxes determined by the taxpayer or by the Secretary as to which returns or lists (or payments under section 6225(c)(2)(B)(i)) are made under this title.
(2) Unpaid taxes payable by stamp.
(A) Omitted stamps. Whenever any article upon which a tax is required to be paid by means of a stamp is sold or removed for sale or use by the manufacturer thereof or whenever any transaction or act upon which a tax is required to be paid by means of a stamp occurs without the use of the proper stamp, it shall be the duty of the Secretary, upon such information as he can obtain, to estimate the amount of tax which has been omitted to be paid and to make assessment therefor upon the person or persons the Secretary determines to be liable for such tax.
(B) Check or money order not duly paid. In any case in which a check or money order received under authority of section 6311 as payment for stamps is not duly paid, the unpaid amount may be immediately assessed as if it were a tax imposed by this title, due at the time of such receipt, from the person who tendered such check or money order.
(3) Erroneous income tax prepayment credits. If on any return or claim for refund of income taxes under subtitle A there is an overstatement of the credit for income tax withheld at the source, or of the amount paid as estimated income tax, the amount so overstated which is allowed against the tax shown on the return or which is allowed as a credit or refund may be assessed by the Secretary in the same manner as in the case of a mathematical or clerical error appearing upon the return, except that the provisions of section 6213(b)(2) (relating to abatement of mathematical or clerical error assessments) shall not apply with regard to any assessment under this paragraph.
(4) Certain orders of criminal restitution.
(A) In general. The Secretary shall assess and collect the amount of restitution under an order pursuant to section 3556 of title 18 for failure to pay any tax imposed under this title in the same manner as if such amount were such tax.
(B) Time of assessment. An assessment of an amount of restitution under an order described in subparagraph (A) shall not be made before all appeals of such order are concluded and the right to make all such appeals has expired.
(C) Restriction on challenge of assessment. The amount of such restitution may not be challenged by the person against whom assessed on the basis of the existence or amount of the underlying tax liability in any proceeding authorized under this title (including in any suit or proceeding in court permitted under section 7422).
(b) Amount not to be assessed.
(c) Compensation of child. Any income tax under chapter 1 assessed against a child, to the extent attributable to amounts includible in the gross income of the child, and not of the parent, solely by reason of section 73(a), shall, if not paid by the child, for all purposes be considered as having also been properly assessed against the parent.
(d) Required reasonable verification of information returns. In any court proceeding, if a taxpayer asserts a reasonable dispute with respect to any item of income reported on an information return filed with the Secretary under subpart B or C of part III of subchapter A of chapter 61 by a third party and the taxpayer has fully cooperated with the Secretary (including providing, within a reasonable period of time, access to and inspection of all witnesses, information, and documents within the control of the taxpayer as reasonably requested by the Secretary), the Secretary shall have the burden of producing reasonable and probative information concerning such deficiency in addition to such information return.
(e) Deficiency proceedings. For special rules applicable to deficiencies of income, estate, gift, and certain excise taxes, see subchapter B.