266 
tribution for the plan year (as in-
creased under paragraph (2)) shall be 
further increased by an amount equal 
to the interest on the amount of the 
underpayment for the period of the 
underpayment, using an interest rate 
equal to the excess of— 
‘‘(i) 175 percent of the Federal 
mid-term rate (as in effect under 
section 1274 for the 1st month of 
such plan year), over 
‘‘(ii) the effective rate of inter-
est for the plan for the plan year. 
‘‘(B) AMOUNT
OF
UNDERPAYMENT, 
PERIOD
OF
UNDERPAYMENT.—For pur-
poses of subparagraph (A)— 
‘‘(i) AMOUNT.—The amount of 
the underpayment shall be the ex-
cess of— 
‘‘(I) the required install-
ment, over 
‘‘(II) the amount (if any) of 
the installment contributed to 
or under the plan on or before
267 
the due date for the install-
ment. 
‘‘(ii) 
PERIOD
OF
UNDER-
PAYMENT.—The period for which 
any interest is charged under this 
paragraph with respect to any 
portion 
of 
the 
underpayment 
shall run from the due date for 
the installment to the date on 
which such portion is contributed 
to or under the plan. 
‘‘(iii) ORDER OF CREDITING CON-
TRIBUTIONS.—For 
purposes 
of 
clause (i)(II), contributions shall 
be credited against unpaid re-
quired installments in the order 
in which such installments are re-
quired to be paid. 
‘‘(C) NUMBER OF REQUIRED INSTALL-
MENTS; DUE
DATES.—For purposes of 
this paragraph— 
‘‘(i) PAYABLE
IN
INSTALL-
MENTS.—There shall be 4 required 
installments for each plan year.
268 
‘‘(ii) TIME FOR PAYMENT OF IN-
STALLMENTS.—The due dates for 
required 
installments 
are 
set 
forth in the following table: 
‘‘In the case of the following 
required installment: 
The due date is: 
1st .....................................................................
April 15 
2nd ...................................................................
July 15 
3rd ....................................................................
October 15 
4th ....................................................................
January 15 of the 
following year 
‘‘(D) AMOUNT OF REQUIRED INSTALL-
MENT.—For purposes of this para-
graph— 
‘‘(i) IN GENERAL.—The amount 
of any required installment shall 
be 25 percent of the required an-
nual payment. 
‘‘(ii) REQUIRED
ANNUAL
PAY-
MENT.—For purposes of clause (i), 
the term ‘required annual pay-
ment’ means the lesser of— 
‘‘(I) 90 percent of the min-
imum required contribution 
(without regard to any waiver 
under section 412(c)) to the
269 
plan for the plan year under 
this section, or 
‘‘(II) in the case of a plan 
year beginning after 2007, 100 
percent of the minimum re-
quired contribution (without 
regard to any waiver under 
section 412(c)) to the plan for 
the preceding plan year. 
Subclause (II) shall not apply if 
the preceding plan year referred 
to in such clause was not a year 
of 12 months. 
‘‘(E) 
FISCAL
YEARS
AND
SHORT 
YEARS.— 
‘‘(i) FISCAL YEARS.—In applying 
this paragraph to a plan year be-
ginning on any date other than 
January 1, there shall be sub-
stituted for the months specified 
in this paragraph, the months 
which correspond thereto. 
‘‘(ii) SHORT
PLAN
YEAR.—This 
subparagraph shall be applied to 
plan years of less than 12 months