Except as otherwise provided in this section, the amount of any tax imposed by this title shall be assessed within 3 years after the return was filed (whether or not such return was filed on or after the date prescribed) or, if the tax is payable by stamp, at any time after such tax became due and before the expiration of 3 years after the date on which any part of such tax was paid, and no proceeding in court without assessment for the collection of such tax shall be begun after the expiration of such period. For purposes of this chapter, the term “return” means the return required to be filed by the taxpayer (and does not include a return of any person from whom the taxpayer has received an item of income, gain, loss, deduction, or credit).

For purposes of this section, a return of tax imposed by this title, except tax imposed by chapter 3, 4, 21, or 24, filed before the last day prescribed by law or by regulations promulgated pursuant to law for the filing thereof, shall be considered as filed on such last day.

(1) Early return For purposes of this section, a return of tax imposed by this title, except tax imposed by chapter 3, 4, 21, or 24, filed before the last day prescribed by law or by regulations promulgated pursuant to law for the filing thereof, shall be considered as filed on such last day.

(2) Return of certain employment and withholding taxes For purposes of this section, if a return of tax imposed by chapter 3, 4, 21, or 24 for any period ending with or within a calendar year is filed before April 15 of the succeeding calendar year, such return shall be considered filed on April 15 of such calendar year.

(3) Return executed by Secretary Notwithstanding the provisions of paragraph (2) of section 6020(b), the execution of a return by the Secretary pursuant to the authority conferred by such section shall not start the running of the period of limitations on assessment and collection.

(4) Return of excise taxes For purposes of this section, the filing of a return for a specified period on which an entry has been made with respect to a tax imposed under a provision of subtitle D (including a return on which an entry has been made showing no liability for such tax for such period) shall constitute the filing of a return of all amounts of such tax which, if properly paid, would be required to be reported on such return for such period.

If a taxpayer fails to include on any return or statement for any taxable year any information with respect to a listed transaction (as defined in section 6707A(c)(2)) which is required under section 6011 to be included with such return or statement, the time for assessment of any tax imposed by this title with respect to such transaction shall not expire before the date which is 1 year after the earlier of—

(1) False return In the case of a false or fraudulent return with the intent to evade tax, the tax may be assessed, or a proceeding in court for collection of such tax may be begun without assessment, at any time.

(2) Willful attempt to evade tax In case of a willful attempt in any manner to defeat or evade tax imposed by this title (other than tax imposed by subtitle A or B), the tax may be assessed, or a proceeding in court for the collection of such tax may be begun without assessment, at any time.

(3) No return In the case of failure to file a return, the tax may be assessed, or a proceeding in court for the collection of such tax may be begun without assessment, at any time.

Where, before the expiration of the time prescribed for the assessment of any tax imposed by this title, except the estate tax provided in chapter 11, both the Secretary and the taxpayer have consented in writing to its assessment after such time, the tax may be assessed at any time prior to the expiration of the period agreed upon. The period so agreed upon may be extended by subsequent agreements in writing made before the expiration of the period previously agreed upon.

(A) In general Where, before the expiration of the time prescribed for the assessment of any tax imposed by this title, except the estate tax provided in chapter 11, both the Secretary and the taxpayer have consented in writing to its assessment after such time, the tax may be assessed at any time prior to the expiration of the period agreed upon. The period so agreed upon may be extended by subsequent agreements in writing made before the expiration of the period previously agreed upon.

(B) Notice to taxpayer of right to refuse or limit extension The Secretary shall notify the taxpayer of the taxpayer’s right to refuse to extend the period of limitations, or to limit such extension to particular issues or to a particular period of time, on each occasion when the taxpayer is requested to provide such consent.

(5) Tax resulting from changes in certain income tax or estate tax credits For special rules applicable in cases where the adjustment of certain taxes allowed as a credit against income taxes or estate taxes results in additional tax, see section 905(c) (relating to the foreign tax credit for income tax purposes) and section 2016 (relating to taxes of foreign countries, States, etc., claimed as credit against estate taxes).

(6) Termination of private foundation status In the case of a tax on termination of private foundation status under section 507, such tax may be assessed, or a proceeding in court for the collection of such tax may be begun without assessment, at any time.

(7) Special rule for certain amended returns Where, within the 60-day period ending on the day on which the time prescribed in this section for the assessment of any tax imposed by subtitle A for any taxable year would otherwise expire, the Secretary receives a written document signed by the taxpayer showing that the taxpayer owes an additional amount of such tax for such taxable year, the period for the assessment of such additional amount shall not expire before the day 60 days after the day on which the Secretary receives such document.

In the case of any information which is required to be reported to the Secretary pursuant to an election under section 1295(b) or under section 1298(f), 6038, 6038A, 6038B, 6038D, 6046, 6046A, or 6048, the time for assessment of any tax imposed by this title with respect to any tax return, event, or period to which such information relates shall not expire before the date which is 3 years after the date on which the Secretary is furnished the information required to be reported under such section.

(A) In general In the case of any information which is required to be reported to the Secretary pursuant to an election under section 1295(b) or under section 1298(f), 6038, 6038A, 6038B, 6038D, 6046, 6046A, or 6048, the time for assessment of any tax imposed by this title with respect to any tax return, event, or period to which such information relates shall not expire before the date which is 3 years after the date on which the Secretary is furnished the information required to be reported under such section.

(B) Application to failures due to reasonable cause If the failure to furnish the information referred to in subparagraph (A) is due to reasonable cause and not willful neglect, subparagraph (A) shall apply only to the item or items related to such failure.

(9) Gift tax on certain gifts not shown on return If any gift of property the value of which (or any increase in taxable gifts required under section 2701(d) which) is required to be shown on a return of tax imposed by chapter 12 (without regard to section 2503(b)), and is not shown on such return, any tax imposed by chapter 12 on such gift may be assessed, or a proceeding in court for the collection of such tax may be begun without assessment, at any time. The preceding sentence shall not apply to any item which is disclosed in such return, or in a statement attached to the return, in a manner adequate to apprise the Secretary of the nature of such item.

If a taxpayer fails to include on any return or statement for any taxable year any information with respect to a listed transaction (as defined in section 6707A(c)(2)) which is required under section 6011 to be included with such return or statement, the time for assessment of any tax imposed by this title with respect to such transaction shall not expire before the date which is 1 year after the earlier of—

(A) the date on which the Secretary is furnished the information so required, or

(B) the date that a material advisor meets the requirements of section 6112 with respect to a request by the Secretary under section 6112(b) relating to such transaction with respect to such taxpayer.

(11) Certain orders of criminal restitution In the case of any amount described in section 6201(a)(4), such amount may be assessed, or a proceeding in court for the collection of such amount may be begun without assessment, at any time.

In the case of any partnership adjustment determined under subchapter C of chapter 63, the period for assessment of any tax imposed under chapter 2 or 2A which is attributable to such adjustment shall not expire before the date that is 1 year after—

(A) in the case of an adjustment pursuant to the decision of a court in a proceeding brought under section 6234, such decision becomes final, or

(B) in any other case, 90 days after the date on which the notice of the final partnership adjustment is mailed under section 6231.

Except as otherwise provided in subsection (c), (e), or (f), in the case of any tax (other than the tax imposed by chapter 11 of subtitle B, relating to estate taxes) for which return is required in the case of a decedent, or by his estate during the period of administration, or by a corporation, the tax shall be assessed, and any proceeding in court without assessment for the collection of such tax shall be begun, within 18 months after written request therefor (filed after the return is made and filed in such manner and such form as may be prescribed by regulations of the Secretary) by the executor, administrator, or other fiduciary representing the estate of such decedent, or by the corporation, but not after the expiration of 3 years after the return was filed. This subsection shall not apply in the case of a corporation unless—

such written request notifies the Secretary that the corporation contemplates dissolution at or before the expiration of such 18-month period, (B) the dissolution is in good faith begun before the expiration of such 18-month period, and (C) the dissolution is completed;

(A) such written request notifies the Secretary that the corporation contemplates dissolution at or before the expiration of such 18-month period, (B) the dissolution is in good faith begun before the expiration of such 18-month period, and (C) the dissolution is completed;

such written request notifies the Secretary that a dissolution has in good faith been begun, and (B) the dissolution is completed; or

(A) such written request notifies the Secretary that a dissolution has in good faith been begun, and (B) the dissolution is completed; or

(3) a dissolution has been completed at the time such written request is made.

Except as otherwise provided in subsection (c)—

In the case of any tax imposed by subtitle A—

(A) General ruleIf the taxpayer omits from gross income an amount properly includible therein and— (i) such amount is in excess of 25 percent of the amount of gross income stated in the return, or (ii) such amount— (I) is attributable to one or more assets with respect to which information is required to be reported under section 6038D (or would be so required if such section were applied without regard to the dollar threshold specified in subsection (a) thereof and without regard to any exceptions provided pursuant to subsection (h)(1) thereof), and (II) is in excess of $5,000, the tax may be assessed, or a proceeding in court for collection of such tax may be begun without assessment, at any time within 6 years after the return was filed.

(B) Determination of gross incomeFor purposes of subparagraph (A)— (i) In the case of a trade or business, the term “gross income” means the total of the amounts received or accrued from the sale of goods or services (if such amounts are required to be shown on the return) prior to diminution by the cost of such sales or services; (ii) An understatement of gross income by reason of an overstatement of unrecovered cost or other basis is an omission from gross income; and (iii) In determining the amount omitted from gross income (other than in the case of an overstatement of unrecovered cost or other basis), there shall not be taken into account any amount which is omitted from gross income stated in the return if such amount is disclosed in the return, or in a statement attached to the return, in a manner adequate to apprise the Secretary of the nature and amount of such item.

(C) Constructive dividends If the taxpayer omits from gross income an amount properly includible therein under section 951(a), the tax may be assessed, or a proceeding in court for the collection of such tax may be done without assessing, at any time within 6 years after the return was filed.

(2) Estate and gift taxes In the case of a return of estate tax under chapter 11 or a return of gift tax under chapter 12, if the taxpayer omits from the gross estate or from the total amount of the gifts made during the period for which the return was filed items includible in such gross estate or such total gifts, as the case may be, as exceed in amount 25 percent of the gross estate stated in the return or the total amount of gifts stated in the return, the tax may be assessed, or a proceeding in court for the collection of such tax may be begun without assessment, at any time within 6 years after the return was filed. In determining the items omitted from the gross estate or the total gifts, there shall not be taken into account any item which is omitted from the gross estate or from the total gifts stated in the return if such item is disclosed in the return, or in a statement attached to the return, in a manner adequate to apprise the Secretary of the nature and amount of such item.

(3) Excise taxes In the case of a return of a tax imposed under a provision of subtitle D, if the return omits an amount of such tax properly includible thereon which exceeds 25 percent of the amount of such tax reported thereon, the tax may be assessed, or a proceeding in court for the collection of such tax may be begun without assessment, at any time within 6 years after the return is filed. In determining the amount of tax omitted on a return, there shall not be taken into account any amount of tax imposed by chapter 41, 42, 43, or 44 which is omitted from the return if the transaction giving rise to such tax is disclosed in the return, or in a statement attached to the return, in a manner adequate to apprise the Secretary of the existence and nature of such item.

If a corporation which is a personal holding company for any taxable year fails to file with its return under chapter 1 for such year a schedule setting forth—

(1) the items of gross income and adjusted ordinary gross income, described in section 543, received by the corporation during such year, and

(2) the names and addresses of the individuals who owned, within the meaning of section 544 (relating to rules for determining stock ownership), at any time during the last half of such year more than 50 percent in value of the outstanding capital stock of the corporation,

If a taxpayer determines in good faith that it is a trust or partnership and files a return as such under subtitle A, and if such taxpayer is thereafter held to be a corporation for the taxable year for which the return is filed, such return shall be deemed the return of the corporation for purposes of this section.

(1) Trusts or partnerships If a taxpayer determines in good faith that it is a trust or partnership and files a return as such under subtitle A, and if such taxpayer is thereafter held to be a corporation for the taxable year for which the return is filed, such return shall be deemed the return of the corporation for purposes of this section.

(2) Exempt organizations If a taxpayer determines in good faith that it is an exempt organization and files a return as such under section 6033, and if such taxpayer is thereafter held to be a taxable organization for the taxable year for which the return is filed, such return shall be deemed the return of the organization for purposes of this section.

(3) DISC If a corporation determines in good faith that it is a DISC (as defined in section 992(a)) and files a return as such under section 6011(c)(2) and if such corporation is thereafter held to be a corporation which is not a DISC for the taxable year for which the return is filed, such return shall be deemed the return of a corporation which is not a DISC for purposes of this section.

In the case of a deficiency attributable to the application to the taxpayer of a net operating loss carryback or a capital loss carryback (including deficiencies which may be assessed pursuant to the provisions of section 6213(b)(3)), such deficiency may be assessed at any time before the expiration of the period within which a deficiency for the taxable year of the net operating loss or net capital loss which results in such carryback may be assessed.

In the case of a deficiency attributable to the application to the taxpayer of a carryback under section 904(c) (relating to carryback and carryover of excess foreign taxes) or under section 907(f) (relating to carryback and carryover of disallowed foreign oil and gas taxes), such deficiency may be assessed at any time before the expiration of one year after the expiration of the period within which a deficiency may be assessed for the taxable year of the excess taxes described in section 904(c) or 907(f) which result in such carryback.

In the case of a deficiency attributable to the application to the taxpayer of a credit carryback (including deficiencies which may be assessed pursuant to the provisions of section 6213(b)(3)), such deficiency may be assessed at any time before the expiration of the period within which a deficiency for the taxable year of the unused credit which results in such carryback may be assessed, or with respect to any portion of a credit carryback from a taxable year attributable to a net operating loss carryback, capital loss carryback, or other credit carryback from a subsequent taxable year, at any time before the expiration of the period within which a deficiency for such subsequent taxable year may be assessed.

(1) In general In the case of a deficiency attributable to the application to the taxpayer of a credit carryback (including deficiencies which may be assessed pursuant to the provisions of section 6213(b)(3)), such deficiency may be assessed at any time before the expiration of the period within which a deficiency for the taxable year of the unused credit which results in such carryback may be assessed, or with respect to any portion of a credit carryback from a taxable year attributable to a net operating loss carryback, capital loss carryback, or other credit carryback from a subsequent taxable year, at any time before the expiration of the period within which a deficiency for such subsequent taxable year may be assessed.

(2) Credit carryback defined For purposes of this subsection, the term “credit carryback” has the meaning given such term by section 6511(d)(4)(C).

In a case where an amount has been applied, credited, or refunded under section 6411 (relating to tentative carryback and refund adjustments) by reason of a net operating loss carryback, a capital loss carryback, or a credit carryback (as defined in section 6511(d)(4)(C)) to a prior taxable year, the period described in subsection (a) of this section for assessing a deficiency for such prior taxable year shall be extended to include the period described in subsection (h) or (j), whichever is applicable; except that the amount which may be assessed solely by reason of this subsection shall not exceed the amount so applied, credited, or refunded under section 6411, reduced by any amount which may be assessed solely by reason of subsection (h) or (j), as the case may be.

For purposes of any tax imposed by section 4912, by chapter 42 (other than section 4940), or by section 4975, the return referred to in this section shall be the return filed by the private foundation, plan, trust, or other organization (as the case may be) for the year in which the act (or failure to act) giving rise to liability for such tax occurred. For purposes of section 4940, such return is the return filed by the private foundation for the taxable year for which the tax is imposed.

(1) In general For purposes of any tax imposed by section 4912, by chapter 42 (other than section 4940), or by section 4975, the return referred to in this section shall be the return filed by the private foundation, plan, trust, or other organization (as the case may be) for the year in which the act (or failure to act) giving rise to liability for such tax occurred. For purposes of section 4940, such return is the return filed by the private foundation for the taxable year for which the tax is imposed.

(2) Certain contributions to section 501(c)(3) organizations In the case of a deficiency of tax of a private foundation making a contribution in the manner provided in section 4942(g)(3) (relating to certain contributions to section 501(c)(3) organizations) attributable to the failure of a section 501(c)(3) organization to make the distribution prescribed by section 4942(g)(3), such deficiency may be assessed at any time before the expiration of one year after the expiration of the period within which a deficiency may be assessed for the taxable year with respect to which the contribution was made.

(3) Certain set-asides described in section 4942(g)(2) In the case of a deficiency attributable to the failure of an amount set aside by a private foundation for a specific project to be treated as a qualifying distribution under the provisions of section 4942(g)(2)(B)(ii), such deficiency may be assessed at any time before the expiration of 2 years after the expiration of the period within which a deficiency may be assessed for the taxable year to which the amount set aside relates.

The period for assessing a deficiency attributable to any election under section 30B(h)(9), 30C(e)(4), 30D(e)(4), 35(g)(11), 40(f), 43, 45B, 45C(d)(4), 45H(g), or 51(j) (or any revocation thereof) shall not expire before the date 1 year after the date on which the Secretary is notified of such election (or revocation).

For period of limitations for assessment and collection in the case of a joint income return filed after separate returns have been filed, see section 6013(b)(3) and (4).

(Aug. 16, 1954, ch. 736, 68A Stat. 803; Pub. L. 85–859, title I, § 165(a), Sept. 2, 1958, 72 Stat. 1313; Pub. L. 85–866, title I, §§ 80, 81, Sept. 2, 1958, 72 Stat. 1662; Pub. L. 86–69, § 3(g), June 25, 1959, 73 Stat. 140; Pub. L. 86–780, § 3(c), Sept. 14, 1960, 74 Stat. 1013; Pub. L. 87–794, title III, § 317(c), Oct. 11, 1962, 76 Stat. 890; Pub. L. 87–834, § 2(e)(1), Oct. 16, 1962, 76 Stat. 971; Pub. L. 87–858, § 3(b)(4), Oct. 23, 1962, 76 Stat. 1137; Pub. L. 88–272, title II, § 225(k)(6), Feb. 26, 1964, 78 Stat. 94; Pub. L. 88–571, § 3(b), Sept. 2, 1964, 78 Stat. 857; Pub. L. 89–44, title VIII, § 810(a), (b), June 21, 1965, 79 Stat. 169; Pub. L. 89–721, §§ 2(f), 3(a), Nov. 2, 1966, 80 Stat. 1150, 1151; Pub. L. 89–809, title I, § 105(f)(3), Nov. 13, 1966, 80 Stat. 1568; Pub. L. 90–225, § 2(c), Dec. 27, 1967, 81 Stat. 731; Pub. L. 91–172, title I, § 101(g)(1)–(3), title V, § 512(e)(1), Dec. 30, 1969, 83 Stat. 525, 639; Pub. L. 91–614, title I, § 102(d)(8), Dec. 31, 1970, 84 Stat. 1842; Pub. L. 92–178, title V, § 504(c), title VI, § 601(d)(1), (e)(2), Dec. 10, 1971, 85 Stat. 551, 558, 560; Pub. L. 93–406, title II, § 1016(a)(14), Sept. 2, 1974, 88 Stat. 930; Pub. L. 94–455, title X, §§ 1031(b)(5), 1035(d)(3), title XIII, §§ 1302(b), 1307(d)(2)(F)(vi), title XIX, § 1906(b)(13)(A), title XXI, § 2107(g)(2)(A), Oct. 4, 1976, 90 Stat. 1623, 1633, 1714, 1728, 1834, 1904; Pub. L. 95–30, title II, § 202(d)(4)(A), (5)(B), May 23, 1977, 91 Stat. 149, 151; Pub. L. 95–227, § 4(d)(4), (5), Feb. 10, 1978, 92 Stat. 23; Pub. L. 95–600, title II, § 212(a), title III, § 321(b)(2), title V, § 504(b)(3), title VII, §§ 701(t)(3)(A), 703(n), (p)(2), Nov. 6, 1978, 92 Stat. 2818, 2835, 2881, 2912, 2943, 2944; Pub. L. 95–628, § 8(c)(1), Nov. 10, 1978, 92 Stat. 3631; Pub. L. 96–222, title I, §§ 102(a)(2)(A), 103(a)(6)(G)(x), Apr. 1, 1980, 94 Stat. 208, 210; Pub. L. 96–223, title I, § 101(g)(1), Apr. 2, 1980, 94 Stat. 253; Pub. L. 97–248, title IV, § 402(c)(5), Sept. 3, 1982, 96 Stat. 667; Pub. L. 98–369, div. A, title I, §§ 131(d)(2), 163(b)(1), title II, § 211(b)(24), title III, § 314(a)(3), title IV, §§ 447(a), 474(r)(39), title VII, § 714(p)(2)(F), title VIII, § 801(d)(14), July 18, 1984, 98 Stat. 664, 697, 757, 787, 817, 846, 965, 997; Pub. L. 99–514, title XVIII, §§ 1810(g)(3), 1847(b)(12)–(14), Oct. 22, 1986, 100 Stat. 2828, 2857; Pub. L. 100–203, title X, §§ 10712(c)(2), 10714(c), Dec. 22, 1987, 101 Stat. 1330–467, 1330–471; Pub. L. 100–418, title I, § 1941(b)(2)(H), Aug. 23, 1988, 102 Stat. 1323; Pub. L. 100–647, title I, § 1008(j)(1), title IV, § 4008(c)(2), Nov. 10, 1988, 102 Stat. 3445, 3653; Pub. L. 101–239, title VII, § 7814(e)(2)(E), Dec. 19, 1989, 103 Stat. 2414; Pub. L. 101–508, title XI, §§ 11511(c)(2), 11602(b), Nov. 5, 1990, 104 Stat. 1388–485, 1388–500; Pub. L. 104–188, title I, §§ 1702(e)(3), 1703(n)(8), 1704(j)(4)(B), Aug. 20, 1996, 110 Stat. 1870, 1877, 1882; Pub. L. 105–34, title V, § 506(b), title XI, § 1145(a), title XII, §§ 1239(e)(2), 1284(a), title XVI, § 1601(g)(2), Aug. 5, 1997, 111 Stat. 855, 985, 1028, 1038, 1092; Pub. L. 105–206, title III, § 3461(b), title VI, §§ 6007(e)(2)(A), 6023(27), July 22, 1998, 112 Stat. 764, 809, 826; Pub. L. 108–357, title IV, § 413(c)(28), title VIII, § 814(a), Oct. 22, 2004, 118 Stat. 1509, 1581; Pub. L. 109–58, title XIII, §§ 1341(b)(4), 1342(b)(4), Aug. 8, 2005, 119 Stat. 1049, 1051; Pub. L. 109–135, title IV, § 403(y), Dec. 21, 2005, 119 Stat. 2629; Pub. L. 110–172, § 7(a)(2)(B), Dec. 29, 2007, 121 Stat. 2482; Pub. L. 110–343, div. B, title II, § 205(d)(3), title IV, § 402(d), Oct. 3, 2008, 122 Stat. 3839, 3854; Pub. L. 111–5, div. B, title I, §§ 1141(b)(4), 1142(b)(7), Feb. 17, 2009, 123 Stat. 328, 331; Pub. L. 111–147, title V, §§ 501(c)(2), (3), 513(a)(1), (2)(A), (b), (c), Mar. 18, 2010, 124 Stat. 106, 111, 112; Pub. L. 111–226, title II, § 218(a), Aug. 10, 2010, 124 Stat. 2403; Pub. L. 111–237, § 3(b)(2), Aug. 16, 2010, 124 Stat. 2498; Pub. L. 113–295, div. A, title II, § 221(a)(2)(E), Dec. 19, 2014, 128 Stat. 4037; Pub. L. 114–27, title IV, § 407(e), June 29, 2015, 129 Stat. 382; Pub. L. 114–41, title II, § 2005(a), July 31, 2015, 129 Stat. 456; Pub. L. 114–74, title XI, § 1101(f)(3), Nov. 2, 2015, 129 Stat. 637; Pub. L. 115–97, title I, § 13403(d)(2), Dec. 22, 2017, 131 Stat. 2137; Pub. L. 115–141, div. U, title II, §§ 201(b)(2), 205(b), title IV, § 401(a)(295), Mar. 23, 2018, 132 Stat. 1172, 1178, 1198.)