‘‘(8) Any inconsistent estate basis.’’. 
(2) INCONSISTENT BASIS REPORTING.—Section 
6662 of such Code is amended by adding at the end 
the following new subsection: 
‘‘(k) INCONSISTENT ESTATE BASIS REPORTING.— 
For purposes of this section, there is an ‘inconsistent es-
tate basis’ if the basis of property claimed on a return 
exceeds the basis as determined under section 1014(f).’’. 
(d) EFFECTIVE DATE.—The amendments made by 
this section shall apply to property with respect to which 
an estate tax return is filed after the date of the enact-
ment of this Act. 
SEC. 2005. CLARIFICATION OF 6-YEAR STATUTE OF LIMITA-
TIONS IN CASE OF OVERSTATEMENT OF 
BASIS. 
(a) IN GENERAL.—Section 6501(e)(1)(B) of the In-
ternal Revenue Code of 1986 is amended— 
(1) by striking ‘‘and’’ at the end of clause (i), 
by redesignating clause (ii) as clause (iii), and by in-
serting after clause (i) the following new clause: 
‘‘(ii) An understatement of gross in-
come by reason of an overstatement of un-
recovered cost or other basis is an omission 
from gross income; and’’, and
(2) by inserting ‘‘(other than in the case of an 
overstatement of unrecovered cost or other basis)’’ 
in clause (iii) (as so redesignated) after ‘‘In deter-
mining the amount omitted from gross income’’. 
(b) EFFECTIVE DATE.—The amendments made by 
this section shall apply to— 
(1) returns filed after the date of the enactment 
of this Act, and 
(2) returns filed on or before such date if the 
period specified in section 6501 of the Internal Rev-
enue Code of 1986 (determined without regard to 
such amendments) for assessment of the taxes with 
respect to which such return relates has not expired 
as of such date. 
SEC. 2006. TAX RETURN DUE DATES. 
(a) DUE DATES FOR RETURNS OF PARTNERSHIPS, 
S CORPORATIONS, AND C CORPORATIONS.— 
(1) PARTNERSHIPS AND S CORPORATIONS.— 
(A) IN GENERAL.—So much of subsection 
(b) of 6072 of the Internal Revenue Code of 
1986 as precedes the second sentence thereof is 
amended to read as follows: 
‘‘(b) RETURNS OF PARTNERSHIPS AND S CORPORA-
TIONS.—Returns of partnerships under section 6031 and 
returns of S corporations under sections 6012 and 6037
made on the basis of the calendar year shall be filed on 
or before the 15th day of March following the close of the 
calendar year, and such returns made on the basis of a 
fiscal year shall be filed on or before the 15th day of the 
third month following the close of the fiscal year.’’. 
(B) CONFORMING
AMENDMENT.—Section 
6072(a) of such Code is amended by striking 
‘‘6017, or 6031’’ and inserting ‘‘or 6017’’. 
(2) CONFORMING AMENDMENTS RELATING TO C 
CORPORATION DUE DATE OF 15TH DAY OF FOURTH 
MONTH FOLLOWING TAXABLE YEAR.— 
(A) Section 170(a)(2)(B) of such Code is 
amended by striking ‘‘third month’’ and insert-
ing ‘‘fourth month’’. 
(B) Section 563 of such Code is amended 
by striking ‘‘third month’’ each place it appears 
and inserting ‘‘fourth month’’. 
(C) Section 1354(d)(1)(B)(i) of such Code 
is amended by striking ‘‘3d month’’ and insert-
ing ‘‘4th month’’. 
(D) Subsections (a) and (c) of section 
6167 of such Code are each amended by strik-
ing ‘‘third month’’ and inserting ‘‘fourth 
month’’.
(E) Section 6425(a)(1) of such Code is 
amended by striking ‘‘third month’’ and insert-
ing ‘‘fourth month’’. 
(F) Subsections (b)(2)(A), (g)(3), and 
(h)(1) of section 6655 of such Code are each 
amended by striking ‘‘3rd month’’ and inserting 
‘‘4th month’’. 
(G) Section 6655(g)(4) of such Code is 
amended by redesignating subparagraph (E) as 
subparagraph (F) and by inserting after sub-
paragraph (D) the following new subparagraph: 
‘‘(E) Subsection (b)(2)(A) shall be applied 
by substituting ‘3rd month’ for ‘4th month’.’’. 
(3) EFFECTIVE DATES.— 
(A) IN GENERAL.—Except as provided in 
subparagraph (B), the amendments made by 
this subsection shall apply to returns for tax-
able years beginning after December 31, 2015. 
(B) SPECIAL RULE FOR C CORPORATIONS 
WITH FISCAL YEARS ENDING ON JUNE 30.—In 
the case of any C corporation with a taxable 
year ending on June 30, the amendments made 
by this subsection shall apply to returns for tax-
able years beginning after December 31, 2025.