[Code of Federal Regulations]
[Title 26, Volume 13]
[Revised as of April 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 26CFR]

[Page 486-494]
 
                       TITLE 26--INTERNAL REVENUE
 
    CHAPTER I--INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY 
                               (CONTINUED)
 
Procedure and Administration--Table of Contents
 
Sec.  1.6662-4  Substantial understatement of income tax.

    (a) In general. If any portion of an underpayment, as defined in 
section 6664(a) and Sec.  1.6664-2, of any income tax imposed under 
subtitle A of the Code that is required to be shown on a return is 
attributable to a substantial understatement of such income tax, there 
is added to the tax an amount equal to 20 percent of such portion. 
Except in the case of any item attributable to a tax shelter (as defined 
in paragraph (g)(2) of this section), an understatement is reduced by 
the portion of the understatement that is attributable to the tax 
treatment of an item for which there is substantial authority, or with 
respect to which there is adequate disclosure. General rules for 
determining the amount of an understatement are set forth in paragraph 
(b) of this section and more specific rules in the case of carrybacks 
and carryovers are set forth in paragraph

[[Page 487]]

(c) of this section. The rules for determining when substantial 
authority exists are set forth in Sec.  1.6662-4(d). The rules for 
determining when there is adequate disclosure are set forth in Sec.  
1.6662-4 (e) and (f). This penalty does not apply to the extent that the 
reasonable cause and good faith exception to this penalty set forth in 
Sec.  1.6664-4 applies.
    (b) Definitions and computational rules--(1) Substantial. An 
understatement (as defined in paragraph (b)(2) of this section) is 
``substantial'' if it exceeds the greater of--
    (i) 10 percent of the tax required to be shown on the return for the 
taxable year (as defined in paragraph (b)(3) of this section); or
    (ii) $5,000 ($10,000 in the case of a corporation other than an S 
corporation (as defined in section 1361(a)(1)) or a personal holding 
company (as defined in section 542)).
    (2) Understatement. Except as provided in paragraph (c)(2) of this 
section (relating to special rules for carrybacks), the term 
``understatement'' means the excess of--
    (i) The amount of the tax required to be shown on the return for the 
taxable year (as defined in paragraph (b)(3) of this section), over
    (ii) The amount of the tax imposed which is shown on the return for 
the taxable year (as defined in paragraph (b)(4) of this section), 
reduced by any rebate (as defined in paragraph (b)(5) of this section).
    The definition of understatement also may be expressed as--

Understatement = X - (Y - Z)
where X = the amount of the tax required to be shown on the return; Y = 
the amount of the tax imposed which is shown on the return; and Z = any 
rebate.

    (3) Amount of the tax required to be shown on the return. The 
``amount of the tax required to be shown on the return'' for the taxable 
year has the same meaning as the ``amount of income tax imposed'' as 
defined in Sec.  1.6664-2(b).
    (4) Amount of the tax imposed which is shown on the return. The 
``amount of the tax imposed which is shown on the return'' for the 
taxable year has the same meaning as the ``amount shown as the tax by 
the taxpayer on his return,'' as defined in Sec.  1.6664-2(c), except 
that--
    (i) There is no reduction for the excess of the amount described in 
Sec.  1.6664-2(c)(1)(i) over the amount described in Sec.  1.6664-
2(c)(1)(ii), and
    (ii) The tax liability shown by the taxpayer on his return is 
recomputed as if the following items had been reported properly:
    (A) Items (other than tax shelter items as defined in Sec.  1.6662-
4(g)(3)) for which there is substantial authority for the treatment 
claimed (as provided in Sec.  1.6662-4(d)).
    (B) Items (other than tax shelter items as defined in Sec.  1.6662-
4(g)(3)) with respect to which there is adequate disclosure (as provided 
in Sec.  1.6662-4 (e) and (f)).
    (C) Tax shelter items (as defined in Sec.  1.6662-4(g)(3)) for which 
there is substantial authority for the treatment claimed (as provided in 
Sec.  1.6662-4(d)), and with respect to which the taxpayer reasonably 
believed that the tax treatment of the items was more likely than not 
the proper tax treatment (as provided in Sec.  1.6662-4(g)(4)).
    (5) Rebate. The term rebate has the meaning set forth in Sec.  
1.6664-2(e), except that--
    (i) ``Amounts not so shown previously assessed (or collected without 
assessment)'' includes only amounts not so shown previously assessed (or 
collected without assessment) as a deficiency, and
    (ii) The amount of the rebate is determined as if any items to which 
the rebate is attributable that are described in paragraph (b)(4) of 
this section had received the proper tax treatment.
    (6) Examples. The following examples illustrate the provisions of 
paragraph (b) of this section. These examples do not take into account 
the reasonable cause exception under Sec.  1.6664-4:

    Example 1. In 1990, Individual A, a calendar year taxpayer, files a 
return for 1989, which shows taxable income of $18,200 and tax liability 
of $2,734. Subsequent adjustments on audit for 1989 increase taxable 
income to $51,500 and tax liability to $12,339. There was substantial 
authority for an item resulting in an adjustment that increases taxable 
income by $5,300. The item is not a tax shelter item. In computing the 
amount of the understatement, the amount of tax shown on A's

[[Page 488]]

return is determined as if the item for which there was substantial 
authority had been given the proper tax treatment. Thus, the amount of 
tax that is treated as shown on A's return is $4,176, i.e., the tax on 
$23,500 ($18,200 taxable income actually shown on A's return plus 
$5,300, the amount of the adjustment for which there was substantial 
authority). The amount of the understatement is $8,163, i.e., $12,339 
(the amount of tax required to be shown) less $4,176 (the amount of tax 
treated as shown on A's return after adjustment for the item for which 
there was substantial authority). Because the $8,163 understatement 
exceeds the greater of 10 percent of the tax required to be shown on the 
return for the year, i.e., $1,234 ($12,339 x .10) or $5,000, A has a 
substantial understatement of income tax for the year.
    Example 2. Individual B, a calendar year taxpayer, files a return 
for 1990 that fails to include income reported on an information return, 
Form 1099, that was furnished to B. The Service detects this omission 
through its document matching program and assesses $3,000 in unreported 
tax liability. B's return is later examined and as a result of the 
examination the Service makes an adjustment to B's return of $4,000 in 
additional tax liability. Assuming there was neither substantial 
authority nor adequate disclosure with respect to the items adjusted, 
there is an understatement of $7,000 with respect to B's return. There 
is also an underpayment of $7,000. (See Sec.  1.6664-2.) The amount of 
the understatement is not reduced by imposition of a negligence penalty 
on the $3,000 portion of the underpayment that is attributable to the 
unreported income. However, if the Services does impose the negligence 
penalty on this $3,000 portion, the Service may only impose the 
substantial understatement penalty on the remaining $4,000 portion of 
the underpayment. (See Sec.  1.6662-2(c), which prohibits stacking of 
accuracy-related penalty components.)

    (c) Special rules in the case of carrybacks and carryovers--(1) In 
general. The penalty for a substantial understatement of income tax 
applies to any portion of an underpayment for a year to which a loss, 
deduction or credit is carried that is attributable to a ``tainted 
item'' for the year in which the carryback or carryover of the loss, 
deduction or credit arises (the ``loss or credit year''). The 
determination of whether an understatement is substantial for a 
carryback or carryover year is made with respect to the return of the 
carryback or carryover year. ``Tainted items'' are taken into account 
with items arising in a carryback or carryover year to determine whether 
the understatement is substantial for that year.
    (2) Understatements for carryback years not reduced by amount of 
carrybacks. The amount of an understatement for a carryback year is not 
reduced on account of a carryback of a loss, deduction or credit to that 
year.
    (3) Tainted items defined--(i) In general. Except in the case of a 
tax shelter item (as defined in paragraph (g)(3) of this section), a 
``tainted item'' is any item for which there is neither substantial 
authority nor adequate disclosure with respect to the loss or credit 
year.
    (ii) Tax shelter items. In the case of a tax shelter item (as 
defined in paragraph (g)(3) of this section), a ``tainted item'' is any 
item for which there is not, with respect to the loss or credit year, 
both substantial authority and a reasonable belief that the tax 
treatment is more likely than not the proper treatment.
    (4) Transition rule for carrybacks to pre-1990 years. A 20 percent 
penalty under section 6662(b)(2) is imposed on any portion of an 
underpayment for a carryback year, the return for which is due (without 
regard to extensions) before January 1, 1990, if--
    (i) That portion is attributable to one or more ``tainted items'' 
(as defined in paragraph (c)(3) of this section) arising in a loss or 
credit year; and
    (ii) The return for the loss or credit year is due (without regard 
to extensions) after December 31, 1989.

The preceding sentence applies only if the understatement in the 
carryback year is substantial. See Example 2 in paragraph (c)(5) of this 
section.
    (5) Examples. The following examples illustrate the rules of 
paragraph (c) of this section regarding carrybacks and carryovers. These 
examples do not take into account the reasonable cause exception under 
Sec.  1.6664-4.

    Example 1. (i) Corporation N, a calendar year taxpayer, is a C 
corporation. N was formed on January 1, 1987, and timely filed the 
following income tax returns:

[[Page 489]]



                                                  [In dollars]
----------------------------------------------------------------------------------------------------------------
                                                                                      Tax Year
                                                                  ----------------------------------------------
                                                                                                          1990
                                                                      1987       1988         1989      (before
                                                                                                         NOLCO)
----------------------------------------------------------------------------------------------------------------
Taxable income...................................................     30,000     100,000    (300,000)     50,000
Tax liability....................................................      4,575      22,250  ...........      7,500
----------------------------------------------------------------------------------------------------------------

    (ii) During 1990, N files Form 1139, Corporation Application for 
Tentative Refund, to carry back the NOL generated in 1989 (NOLCB). N 
received refunds of $4,575 for 1987 and $22,250 for 1988.
    (iii) For tax year 1990, N carries over $50,000 of the 1989 loss to 
offset $50,000 of income earned in 1990 and reduce taxable income to 
zero. N would have reported $7,500 of tax liability for 1990 if it were 
not for use of the net operating loss carryover (NOLCO). N assumes there 
is a remaining NOLCO of $120,000 to be applied for tax year 1991.
    (iv) In June 1991, the Service completes its examination of the 1989 
loss year return and makes the following adjustment:

Taxable income per 1989 return............................    ($300,000)
Adjustment: Unreported income.............................      310,000
                                                           -------------
Corrected taxable income..................................      $10,000
Corrected tax liability...................................       $1,500


    (v) There was not substantial authority for N's treatment of the 
items comprising the 1989 adjustment and N did not make adequate 
disclosure.
    (vi) As a result of the adjustment to the 1989 return, N had an 
understatement of $4,575 for tax year 1987; an understatement of $22,250 
for tax year 1988; an understatement of $1,500 for tax year 1989; and an 
understatement of $7,500 for tax year 1990. Only the $22,250 
understatement for 1988 is a substantial understatement, i.e., it 
exceeds the greater of (a) $2,225 (10 percent of the tax required to be 
shown on the return for the taxable year (.10 X $22,250)) or (b) 
$10,000. The underpayment for 1988 is subject to a penalty rate of 20 
percent.
    Example 2. The facts are the same as in Example 1, except that in 
addition to examining the 1989 return, the Service also examines the 
1987 return and makes an adjustment that results in an understatement. 
(This adjustment is unrelated to the adjustment on the 1987 return for 
the disallowance of the NOLCB from 1989.) If the understatement 
resulting from the adjustment to the 1987 return, when combined with the 
understatement resulting from the disallowance of the NOLCB from 1989, 
exceeds the greater of (a) 10 percent of the tax required to be shown on 
the return for 1987 or (b) $10,000, the underpayment for 1987 will also 
be subject to a substantial understatement penalty. The portion of the 
underpayment attributable to the adjustment unrelated to the 
disallowance of the NOLCB will be subject to a penalty rate of 25 
percent under former section 6661. The portion of the underpayment 
attributable to the disallowance of the NOLCB will be subject to a 
penalty rate of 20 percent under section 6662.
    Example 3. Individual P, a calendar year single taxpayer, files his 
1990 return reporting taxable income of $10,000 and a tax liability of 
$1,504. An examination of the 1990 return results in an adjustment for 
unreported income of $25,000. There was not substantial authority for 
P's failure to report the income, and P did not make adequate disclosure 
with respect to the unreported income. P's correct tax liability for 
1990 is determined to be $7,279, resulting in an understatement of 
$5,775 (the difference between the amount of tax required to be shown on 
the return ($7,279) and the tax shown on the return ($1,504)). Because 
the understatement exceeds the greater of (a) $728 (10 percent of the 
tax required to be shown on the return (.10 x $7,279)) or (b) $5,000, 
the understatement is substantial. Subsequently, P files his 1993 return 
showing a net operating loss. The loss is carried back to his 1990 
return, reducing his taxable income for 1990 to zero. However, the 
amount of the understatement for 1990 is not reduced on account of the 
NOLCB to that year. P is subject to the 20 percent penalty rate under 
section 6662 on the underpayment attributable to the substantial 
understatement for 1990, notwithstanding that the tax required to be 
shown on the return for that year, after application of the NOLCB, is 
zero.

    (d) Substantial authority--(1) Effect of having substantial 
authority. If there is substantial authority for the tax treatment of an 
item, the item is treated as if it were shown properly on the return for 
the taxable year in computing the amount of the tax shown on the return. 
Thus, for purposes of section 6662(d), the tax attributable to the item 
is not included in the understatement for that year. (For special rules 
relating to tax shelter items see Sec.  1.6662-4(g).)
    (2) Substantial authority standard. The substantial authority 
standard is an objective standard involving an analysis of the law and 
application of the law to relevant facts. The substantial authority 
standard is less stringent than the more likely than not standard (the 
standard that is met when there is a greater than 50-percent likelihood 
of the position being upheld), but more stringent than the reasonable 
basis standard as defined in Sec.  1.6662-3(b)(3).

[[Page 490]]

The possibility that a return will not be audited or, if audited, that 
an item will not be raised on audit, is not relevant in determining 
whether the substantial authority standard (or the reasonable basis 
standard) is satisfied.
    (3) Determination of whether substantial authority is present --(i) 
Evaluation of authorities. There is substantial authority for the tax 
treatment of an item only if the weight of the authorities supporting 
the treatement is substantial in relation to the weight of authorities 
supporting contrary treatment. All authorities relevant to the tax 
treatment of an item, including the authorities contrary to the 
treatment, are taken into account in determining whether substantial 
authority exists. The weight of authorities is determined in light of 
the pertinent facts and circumstances in the manner prescribed by 
paragraph (d)(3)(ii) of this section. There may be substantial authority 
for more than one position with respect to the same item. Because the 
substantial authority standard is an objective standard, the taxpayer's 
belief that there is substantial authority for the tax treatment of an 
item is not relevant in determining whether there is substantial 
authority for that treatment.
    (ii) Nature of analysis. The weight accorded an authority depends on 
its relevance and persuasiveness, and the type of document providing the 
authority. For example, a case or revenue ruling having some facts in 
common with the tax treatment at issue is not particularly relevant if 
the authority is materially distinguishable on its facts, or is 
otherwise inapplicable to the tax treatment at issue. An authority that 
merely states a conclusion ordinarily is less persuasive than one that 
reaches its conclusion by cogently relating the applicable law to 
pertinent facts. The weight of an authority from which information has 
been deleted, such as a private letter ruling, is diminished to the 
extent that the deleted information may have affected the authority's 
conclusions. The type of document also must be considered. For example, 
a revenue ruling is accorded greater weight than a private letter ruling 
addressing the same issue. An older private letter ruling, technical 
advice memorandum, general counsel memorandum or action on decision 
generally must be accorded less weight than a more recent one. Any 
document described in the preceding sentence that is more than 10 years 
old generally is accorded very little weight. However, the 
persuasiveness and relevance of a document, viewed in light of 
subsequent developments, should be taken into account along with the age 
of the document. There may be substantial authority for the tax 
treatment of an item despite the absence of certain types of authority. 
Thus, a taxpayer may have substantial authority for a position that is 
supported only by a well-reasoned construction of the applicable 
statutory provision.
    (iii) Types of authority. Except in cases described in paragraph 
(d)(3)(iv) of this section concerning written determinations, only the 
following are authority for purposes of determining whether there is 
substantial authority for the tax treatment of an item: Applicable 
provisions of the Internal Revenue Code and other statutory provisions; 
proposed, temporary and final regulations construing such statues; 
revenue rulings and revenue procedures; tax treaties and regulations 
thereunder, and Treasury Department and other official explanations of 
such treaties; court cases; congressional intent as reflected in 
committee reports, joint explanatory statements of managers included in 
conference committee reports, and floor statements made prior to 
enactment by one of a bill's managers; General Explanations of tax 
legislation prepared by the Joint Committee on Taxation (the Blue Book); 
private letter rulings and technical advice memoranda issued after 
October 31, 1976; actions on decisions and general counsel memoranda 
issued after March 12, 1981 (as well as general counsel memoranda 
published in pre-1955 volumes of the Cumulative Bulletin); Internal 
Revenue Service information or press releases; and notices, 
announcements and other administrative pronouncements published by the 
Service in the Internal Revenue Bulletin. Conclusions reached in 
treatises, legal periodicals, legal opinions or opinions rendered by tax 
professionals

[[Page 491]]

are not authority. The authorities underlying such expressions of 
opinion where applicable to the facts of a particular case, however, may 
give rise to substantial authority for the tax treatment of an item. 
Notwithstanding the preceding list of authorities, an authority does not 
continue to be an authority to the extent it is overruled or modified, 
implicitly or explicitly, by a body with the power to overrule or modify 
the earlier authority. In the case of court decisions, for example, a 
district court opinion on an issue is not an authority if overruled or 
reversed by the United States Court of Appeals for such district. 
However, a Tax Court opinion is not considered to be overruled or 
modified by a court of appeals to which a taxpayer does not have a right 
of appeal, unless the Tax Court adopts the holding of the court of 
appeals. Similarly, a private letter ruling is not authority if revoked 
or if inconsistent with a subsequent proposed regulation, revenue ruling 
or other administrative pronouncement published in the Internal Revenue 
Bulletin.
    (iv) Special rules--(A) Written determinations. There is substantial 
authority for the tax treatment of an item by a taxpayer if the 
treatment is supported by the conclusion of a ruling or a determination 
letter (as defined in Sec.  301.6110-2 (d) and (e)) issued to the 
taxpayer, by the conclusion of a technical advice memorandum in which 
the taxpayer is named, or by an affirmative statement in a revenue 
agent's report with respect to a prior taxable year of the taxpayer 
(``written determinations''). The preceding sentence does not apply, 
however, if--
    (1) There was a misstatement or omission of a material fact or the 
facts that subsequently develop are materially different from the facts 
on which the written determination was based, or
    (2) The written determination was modified or revoked after the date 
of issuance by--
    (i) A notice to the taxpayer to whom the written determination was 
issued,
    (ii) The enactment of legislation or ratification of a tax treaty,
    (iii) A decision of the United States Supreme Court,
    (iv) The issuance of temporary or final regulations, or
    (v) The issuance of a revenue ruling, revenue procedure, or other 
statement published in the Internal Revenue Bulletin.

Except in the case of a written determination that is modified or 
revoked on account of Sec.  1.6662-4(d)(3)(iv)(A)(1), a written 
determination that is modified or revoked as described in Sec.  1.6662-
4(d)(3)(iv)(A)(2) ceases to be authority on the date, and to the extent, 
it is so modified or revoked. See section 6404(f) for rules which 
require the Secretary to abate a penalty that is attributable to 
erroneous written advice furnished to a taxpayer by an officer or 
employee of the Internal Revenue Service.
    (B) Taxpayer's jurisdiction. The applicability of court cases to the 
taxpayer by reason of the taxpayer's residence in a particular 
jurisdiction is not taken into account in determining whether there is 
substantial authority for the tax treatment of an item. Notwithstanding 
the preceding sentence, there is substantial authority for the tax 
treatment of an item if the treatment is supported by controlling 
precedent of a United States Court of Appeals to which the taxpayer has 
a right of appeal with respect to the item.
    (C) When substantial authority determined. There is substantial 
authority for the tax treatment of an item if there is substantial 
authority at the time the return containing the item is filed or there 
was substantial authority on the last day of the taxable year to which 
the return relates.
    (v) Substantial authority for tax returns due before January 1, 
1990. There is substantial authority for the tax treatment of an item on 
a return that is due (without regard to extensions) after December 31, 
1982 and before January 1, 1990, if there is substantial authority for 
such treatment under either the provisions of paragraph (d)(3)(iii) of 
this section (which set forth an expanded list of authorities) or of 
Sec.  1.6661-3(b)(2) (which set forth a narrower list of authorities). 
Under either list of authorities, authorities both for and against the 
position must be taken into account.
    (e) Disclosure of certain information--(1) Effect of adequate 
disclosure. Items

[[Page 492]]

for which there is adequate disclosure as provided in this paragraph (e) 
and in paragraph (f) of this section are treated as if such items were 
shown properly on the return for the taxable year in computing the 
amount of the tax shown on the return. Thus, for purposes of section 
6662(d), the tax attributable to such items is not included in the 
understatement for that year.
    (2) Circumstances where disclosure will not have an effect. The 
rules of paragraph (e)(1) of this section do not apply where the item or 
position on the return--
    (i) Does not have a reasonable basis (as defined in Sec.  1.6662-
3(b)(3));
    (ii) Is attributable to a tax shelter (as defined in section 
6662(d)(2)(C)(iii) and paragraph (g)(2) of this section); or
    (iii) Is not properly substantiated, or the taxpayer failed to keep 
adequate books and records with respect to the item or position.
    (3) Restriction for corporations. For purposes of paragraph 
(e)(2)(i) of this section, a corporation will not be treated as having a 
reasonable basis for its tax treatment of an item attributable to a 
multi-party financing transaction entered into after August 5, 1997, if 
the treatment does not clearly reflect the income of the corporation.
    (f) Method of making adequate disclosure--(1) Disclosure statement. 
Disclosure is adequate with respect to an item (or group of similar 
items, such as amounts paid or incurred for supplies by a taxpayer 
engaged in business) or a position on a return if the disclosure is made 
on a properly completed form attached to the return or to a qualified 
amended return (as defined in Sec.  1.6664-2(c)(3)) for the taxable 
year. In the case of an item or position other than one that is contrary 
to a regulation, disclosure must be made on Form 8275 (Disclosure 
Statement); in the case of a position contrary to a regulation, 
disclosure must be made on Form 8275-R (Regulation Disclosure 
Statement).
    (2) Disclosure on return. The Commissioner may by annual revenue 
procedure (or otherwise) prescribe the circumstances under which 
disclosure of information on a return (or qualified amended return) in 
accordance with applicable forms and instructions is adequate. If the 
revenue procedure does not include an item, disclosure is adequate with 
respect to that item only if made on a properly completed Form 8275 or 
8275-R, as appropriate, attached to the return for the year or to a 
qualified amended return.
    (3) Recurring item. Disclosure with respect to a recurring item, 
such as the basis of recovery property, must be made for each taxable 
year in which the item is taken into account.
    (4) Carrybacks and carryovers. Disclosure is adequate with respect 
to an item which is included in any loss, deduction or credit that is 
carried to another year only if made in connection with the return (or 
qualified amended return) for the taxable year in which the carryback or 
carryover arises (the ``loss or credit year''). Disclosure is not also 
required in connection with the return for the taxable year in which the 
carryback or carryover is taken into account.
    (5) Pass-through entities. Disclosure in the case of items 
attributable to a pass-through entity (pass-through items) is made with 
respect to the return of the entity, except as provided in this 
paragraph (f)(5). Thus, disclosure in the case of pass-through items 
must be made on a Form 8275 or 8275-R, as appropriate, attached to the 
return (or qualified amended return) of the entity, or on the entity's 
return in accordance with the revenue procedure described in paragraph 
(f)(2) of this section, if applicable. A taxpayer (i.e., partner, 
shareholder, beneficiary, or holder of a residual interest in a REMIC) 
also may make adequate disclosure with respect to a pass-through item, 
however, if the taxpayer files a properly completed Form 8275 or 8275-R, 
as appropriate, in duplicate, one copy attached to the taxpayer's return 
(or qualified amended return) and the other copy filed with the Internal 
Revenue Service Center with which the return of the entity is required 
to be filed. Each Form 8275 or 8275-R, as appropriate, filed by the 
taxpayer should relate to the pass-through items of only one entity. For 
purposes of this paragraph (f)(5), a pass-through entity is a 
partnership, S corporation (as defined in section 1361(a)(1)), estate, 
trust, regulated investment company

[[Page 493]]

(as defined in section 851(a)), real estate investment trust (as defined 
in section 856(a)), or real estate mortgage investment conduit 
(``REMIC'') (as defined in section 860D(a)).
    (g) Items relating to tax shelters--(1) In general--(i) Noncorporate 
taxpayers. Tax shelter items (as defined in paragraph (g)(3) of this 
section) of a taxpayer other than a corporation are treated for purposes 
of this section as if such items were shown properly on the return for a 
taxable year in computing the amount of tax shown on the return, and 
thus the tax attributable to such items is not included in the 
understatement for the year, if--
    (A) There is substantial authority (as provided in paragraph (d) of 
this section) for the tax treatment of that item; and
    (B) The taxpayer reasonably believed at the time the return was 
filed that the tax treatment of that item was more likely than not the 
proper treatment.
    (ii) Corporate taxpayers--(A) In general. Except as provided in 
paragraph (g)(1)(ii)(B) of this section, all tax shelter items (as 
defined in paragraph (g)(3) of this section) of a corporation are taken 
into account in computing the amount of any understatement.
    (B) Special rule for transactions occurring prior to December 9, 
1994. The tax shelter items of a corporation arising in connection with 
transactions occurring prior to December 9, 1994 are treated for 
purposes of this section as if such items were shown properly on the 
return if the requirements of paragraph (g)(1)(i) are satisfied with 
respect to such items.
    (iii) Disclosure irrelevant. Disclosure made with respect to a tax 
shelter item of either a corporate or noncorporate taxpayer does not 
affect the amount of an understatement.
    (iv) Cross-reference. See Sec.  1.6664-4(f) for certain rules 
regarding the availability of the reasonable cause and good faith 
exception to the substantial understatement penalty with respect to tax 
shelter items of corporations.
    (2) Tax shelter--(i) In general. For purposes of section 6662(d), 
the term ``tax shelter'' means--
    (A) A partnership or other entity (such as a corporation or trust),
    (B) An investment plan or arrangement, or
    (C) Any other plan or arrangement,

if the principal purpose of the entity, plan or arrangement, based on 
objective evidence, is to avoid or evade Federal income tax. The 
principal purpose of an entity, plan or arrangement is to avoid or evade 
Federal income tax if that purpose exceeds any other purpose. Typical of 
tax shelters are transactions structured with little or no motive for 
the realization of economic gain, and transactions that utilize the 
mismatching of income and deductions, overvalued assets or assets with 
values subject to substantial uncertainty, certain nonrecourse 
financing, financing techniques that do not conform to standard 
commercial business practices, or the mischaracterization of the 
substance of the transaction. The existence of economic substance does 
not of itself establish that a transaction is not a tax shelter if the 
transaction includes other characteristics that indicate it is a tax 
shelter.
    (ii) Principal purpose. The principal purpose of an entity, plan or 
arrangement is not to avoid or evade Federal income tax if the entity, 
plan or arrangement has as its purpose the claiming of exclusions from 
income, accelerated deductions or other tax benefits in a manner 
consistent with the statute and Congressional purpose. For example, an 
entity, plan or arrangement does not have as its principal purpose the 
avoidance or evasion of Federal income tax solely as a result of the 
following uses of tax benefits provided by the Internal Revenue Code: 
the purchasing or holding of an obligation bearing interest that is 
excluded from gross income under section 103; taking an accelerated 
depreciation allowance under section 168; taking the percentage 
depletion allowance under section 613 or section 613A; deducting 
intangible drilling and development costs as expenses under section 
263(c); establishing a qualified retirement plan under sections 401-409; 
claiming the possession tax credit under section 936; or claiming tax 
benefits available by reason of an election under 992 to be taxed as a 
domestic international sales corporation (``DISC''), under section 
927(f)(1) to be taxed as a foreign sales

[[Page 494]]

corporation (``FSC''), or under section 1362 to be taxed as an S 
corporation.
    (3) Tax shelter item. An item of income, gain, loss, deduction or 
credit is a ``tax shelter item'' if the item is directly or indirectly 
attributable to the principal purpose of a tax shelter to avoid or evade 
Federal income tax. Thus, if a partnership is established for the 
principal purpose of avoiding or evading Federal income tax by acquiring 
and overstating the basis of property for purposes of claiming 
accelerated depreciation, the depreciation with respect to the property 
is a tax shelter item. However, a deduction claimed in connection with a 
separate transaction carried on by the same partnership is not a tax 
shelter item if the transaction does not constitute a plan or 
arrangement the principal purpose of which is to avoid or evade tax.
    (4) Reasonable belief--(i) In general. For purposes of section 
6662(d) and paragraph (g)(1)(i)(B) of this section (pertaining to tax 
shelter items of noncorporate taxpayers), a taxpayer is considered 
reasonably to believe that the tax treatment of an item is more likely 
than not the proper tax treatment if (without taking into account the 
possibility that a return will not be audited, that an issue will not be 
raised on audit, or that an issue will be settled)--
    (A) The taxpayer analyzes the pertinent facts and authorities in the 
manner described in paragraph (d)(3)(ii) of this section, and in 
reliance upon that analysis, reasonably concludes in good faith that 
there is a greater than 50-percent likelihood that the tax treatment of 
the item will be upheld if challenged by the Internal Revenue Service; 
or
    (B) The taxpayer reasonably relies in good faith on the opinion of a 
professional tax advisor, if the opinion is based on the tax advisor's 
analysis of the pertinent facts and authorities in the manner described 
in paragraph (d)(3)(ii) of this section and unambiguously states that 
the tax advisor concludes that there is a greater than 50-percent 
likelihood that the tax treatment of the item will be upheld if 
challenged by the Internal Revenue Service.
    (ii) Facts and circumstances; reliance on professional tax advisor. 
All facts and circumstances must be taken into account in determining 
whether a taxpayer satisfies the requirements of paragraph (g)(4)(i) of 
this section. However, in no event will a taxpayer be considered to have 
reasonably relied in good faith on the opinion of a professional tax 
advisor for purposes of paragraph (g)(4)(i)(B) of this section unless 
the requirements of Sec.  1.6664-4(c)(1) are met. The fact that the 
requirements of Sec.  1.6664-4(c)(1) are satisfied will not necessarily 
establish that the taxpayer reasonably relied on the opinion in good 
faith. For example, reliance may not be reasonable or in good faith if 
the taxpayer knew, or should have known, that the advisor lacked 
knowledge in the relevant aspects of Federal tax law.
    (5) Pass-through entities. In the case of tax shelter items 
attributable to a pass-through entity, the actions described in 
paragraphs (g)(4)(i)(A) and (B) of this section, if taken by the entity, 
are deemed to have been taken by the taxpayer and are considered in 
determining whether the taxpayer reasonably believed that the tax 
treatment of an item was more likely than not the proper tax treatment.

[T.D. 8381, 56 FR 67499, Dec. 31, 1991; T.D. 8381, 57 FR 6165, Feb. 20, 
1992, as amended by T.D. 8617, 60 FR 45665, Sept. 1, 1995; T.D. 8790, 63 
FR 66435, Dec. 2, 1998; T.D. 9109, 68 FR 75128, Dec. 30, 2003]