Adjustment factor. The adjustment factor is a percentage equal to -
(1) The excess of 100 percent, over
(2) The product of -
(i) 59 percent, and
(ii) The sum of the maximum rate in effect under section 1 applicable to individuals and the maximum rate in effect under section 1411 applicable to individuals for the month to which the adjusted applicable Federal rate applies.
26 CFR § 1.382-12
In general. The long-term tax-exempt rate for an ownership change is the highest of the adjusted Federal long-term rates in effect for any month in the 3-calendar-month period ending with the calendar month in which the change date occurs. For purposes of the previous sentence, the adjusted Federal long-term rate is the Federal long-term rate determined under section 1274(d) (without regard to paragraphs (2) and (3) thereof), adjusted for differences between rates on long-term taxable and tax-exempt obligations. The Secretary calculates the adjusted Federal long-term rate as provided in paragraph (b) of this section. The Internal Revenue Service publishes the long-term tax-exempt rate and the adjusted Federal long-term rate for each month in the Internal Revenue Bulletin (see 601.601(d)(2)(ii) of this chapter).