Section 6166(b)(1)(B) provides:

(b) Definitions and special rules

(1) Interest in closely held business

For purposes of this section, the term "interest in a closely held business" means-

. . . . . . . . . . . .

(B) an interest as a partner in a partnership carrying on a trade or business, if-

(i) 20 percent or more of the total capital interest in such partnership is included in determining the gross estate of the decedent, or

(ii) such partnership had 45 or fewer partners;