(a) Income taxes—(1) General rule. (i) If a taxpayer omits from the gross income stated in the return of a tax imposed by subtitle A of the Internal Revenue Code an amount properly includible therein that is in excess of 25 percent of the gross income so stated, the tax may be assessed, or a proceeding in court for the collection of that tax may be begun without assessment, at any time within 6 years after the return was filed.

(ii) For purposes of paragraph (a)(1)(i) of this section, the term gross income, as it relates to a trade or business, means the total of the amounts received or accrued from the sale of goods or services, to the extent required to be shown on the return, without reduction for the cost of those goods or services.

(iii) For purposes of paragraph (a)(1)(i) of this section, the term gross income, as it relates to any income other than from the sale of goods or services in a trade or business, has the same meaning as provided under section 61(a), and includes the total of the amounts received or accrued, to the extent required to be shown on the return. In the case of amounts received or accrued that relate to the disposition of property, and except as provided in paragraph (a)(1)(ii) of this section, gross income means the excess of the amount realized from the disposition of the property over the unrecovered cost or other basis of the property. Consequently, except as provided in paragraph (a)(1)(ii) of this section, an understated amount of gross income resulting from an overstatement of unrecovered cost or other basis constitutes an omission from gross income for purposes of section 6501(e)(1)(A)(i).

(iv) An amount shall not be considered as omitted from gross income if information sufficient to apprise the Commissioner of the nature and amount of the item is disclosed in the return, including any schedule or statement attached to the return.

(2) [Reserved]

(b) Estate and gift taxes—(1) If the taxpayer omits from the gross estate as stated in the estate tax return, or from the total amount of the gifts made during the period for which the gift tax return was filed (see § 25.6019-1 of this chapter) as stated in the gift tax return, an item or items properly includible therein the amount of which is in excess of 25 percent of the gross estate as stated in the estate tax return, or 25 percent of the total amount of the gifts as stated in the gift tax return, the tax may be assessed, or a proceeding in court for the collection thereof may be begun without assessment, at any time within 6 years after the estate tax or gift tax return, as applicable, was filed.

(2) For purposes of this paragraph (b), an item disclosed in the return or in any schedule or statement attached to the return in a manner sufficient to apprise the Commissioner of the nature and amount thereof shall not be taken into account in determining items omitted from the gross estate or total gifts, as the case may be. Further, there shall not be taken into account in computing the 25 percent omission from the gross estate stated in the estate tax return or from the total gifts stated in the gift tax return, any increases in the valuation of assets disclosed on the return.

(c) Excise taxes—(1) In general. If the taxpayer omits from a return of a tax imposed under a provision of subtitle D an amount properly includible thereon, which amount is in excess of 25 percent of the amount of tax reported thereon, the tax may be assessed or a proceeding in court for the collection thereof may be begun without assessment, at any time within 6 years after the return was filed. For special rules relating to chapter 41, 42, 43 and 44 taxes, see paragraphs (c)(2), (3), (4), and (5) of this section.

(2) Chapter 41 excise taxes. If an organization discloses an expenditure in its return (or in a schedule or statement attached thereto) in a manner sufficient to apprise the Commissioner of the existence and nature of the expenditure, the three-year limitation on assessment and collection described in section 6501(a) shall apply with respect to any tax under chapter 41 arising from the expenditure. If a taxpayer fails to so disclose an expenditure in its return (or in a schedule or statement attached thereto), the tax arising from the expenditure not so disclosed may be assessed, or a proceeding in court for the collection of the tax may be begun without assessment, at any time within 6 years after the return was filed.

(3) Chapter 42 excise taxes. (i) If a private foundation omits from its annual return with respect to the tax imposed by section 4940 an amount of tax properly includible therein that is in excess of 25 percent of the amount of tax imposed by section 4940 that is reported on the return, the tax may be assessed, or a proceeding in court for the collection of the tax may be begun without assessment, at any time within 6 years after the return was filed. If a private foundation discloses in its return (or in a schedule or statement attached thereto) the nature, source, and amount of any income giving rise to any omitted tax, the tax arising from the income shall be counted as reported on the return in computing whether the foundation has omitted more than 25 percent of the tax reported on its return.

(ii) If a private foundation, trust, or other organization (as the case may be) discloses an item in its return (or in a schedule or statement attached thereto) in a manner sufficient to apprise the Commissioner of the existence and nature of the item, the three-year limitation on assessment and collection described in section 6501(a) shall apply with respect to any tax imposed under sections 4941(a), 4942(a), 4943(a), 4944(a), 4945(a), 4951(a), 4952(a), 4953 and 4958, arising from any transaction disclosed by the item. If a private foundation, trust, or other organization (as the case may be) fails to so disclose an item in its return (or in a schedule or statement attached thereto), the tax arising from any transaction not so disclosed may be assessed or a proceeding in court for the collection of the tax may be begun without assessment, at any time within 6 years after the return was filed.

(4) Chapter 43 excise taxes. If a taxpayer discloses an item in its return (or in a schedule or statement attached thereto) in a manner sufficient to apprise the Commissioner of the existence and nature of the item, the three-year limitation on assessment and collection described in section 6501(a) shall apply with respect to any tax imposed under sections 4971(a), 4972, 4973, 4974 and 4975(a), arising from any transaction disclosed by the item. If a taxpayer fails to so disclose an item in its return (or in a schedule or statement attached thereto), the tax arising from any transaction not so disclosed may be assessed, or a proceeding in court for the collection of the tax may be begun without assessment, at any time within 6 years after the return was filed. The applicable return for the tax under sections 4971, 4972, 4973 and 4974, is the return designated by the Commissioner for reporting the respective tax. The applicable return for the tax under section 4975 is the return filed by the plan used to report the act giving rise to the tax.

(5) Chapter 44 excise taxes. If a real estate investment trust omits from its annual return with respect to the tax imposed by section 4981 an amount of tax properly includible therein that is in excess of 25 percent of the amount of tax imposed by section 4981 that is reported on the return, the tax may be assessed, or a proceeding in court for the collection of the tax may be begun without assessment, at any time within 6 years after the return was filed. If a real estate investment trust discloses in its return (or in a schedule or statement attached thereto) the nature, source, and amount of any income giving rise to any omitted tax, the tax arising from the income shall be counted as reported on the return in computing whether the trust has omitted more than 25 percent of the tax reported on its return.

(d) Exception. The provisions of this section do not limit the application of section 6501(c).

(e) Effective/applicability date—(1) Income taxes. Paragraph (a) of this section applies to taxable years with respect to which the period for assessing tax was open on or after September 24, 2009.

(2) Estate, gift and excise taxes. Paragraphs (b) through (d) of this section continue to apply as they did prior to being removed inadvertently on September 28, 2009. Specifically, paragraph (b) of this section applies to returns filed on or after May 2, 1956, except for the amendment to paragraph (b)(1) of this section that applies to returns filed on or after December 29, 1972. Paragraph (c) of this section applies to returns filed on or after October 7, 1982, except for the amendment to paragraph (c)(3)(ii) of this section that applies to returns filed on or after January 10, 2001. Paragraph (d) of this section applies to returns filed on or after May 2, 1956.