26 CFR §1.382-12

1. (a)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).
2. (b)Adjusted Federal long-term rate. The adjusted Federal long-term rate for a calendar month is the product of the Federal long-term rate determined under section 1274(d) for that month, based on annual compounding, multiplied by the adjustment factor described in paragraph (c) of this section.
3. (c)Adjustment factor. The adjustment factor is a percentage equal to—
   1. (1)The excess of 100 percent, over
   2. (2)The product of—
      1. (i)59 percent, and
      2. (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.
4. (d)Effective/applicability date. The rules of this section apply to the determination of the long-term tax-exempt rate and the adjusted Federal long-term rate beginning with the rates determined during August 2016 that apply during September 2016.