26 USC 244 - Dividends received on certain preferred stock

(a) General rule 
In the case of a corporation, there shall be allowed as a deduction an amount computed as follows:
(1) First determine the amount received as dividends on the preferred stock of a public utility which is subject to taxation under this chapter and with respect to which the deduction provided in section 247 for dividends paid is allowable.
(2) Then multiply the amount determined under paragraph (1) by the fraction
(A) the numerator of which is 14 percent, and

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(B) the denominator of which is that percentage which equals the highest rate of tax specified in section 11 (b).
(3) Finally ascertain the amount which is 70 percent of the excess of
(A) the amount determined under paragraph (1), over
(B) the amount determined under paragraph (2).
(b) Exception 
If the dividends described in subsection (a)(1) are qualifying dividends (as defined in section 243 (b)(1), but determined without regard to section 243 (d)(4))
(1) subsection (a) shall be applied separately to such qualifying dividends, and
(2) for purposes of subsection (a)(3), the percentage applicable to such qualifying dividends shall be 100 percent in lieu of 70 percent.