significant ownership interest
(3) Related person For purposes of this subsection, a person is a related person with respect to the taxpayer if a significant ownership interest in either the taxpayer or such person is held by the other, or if a third person has a significant ownership interest in both the taxpayer and such person. For purposes of the preceding sentence, the term “significant ownership interest” means— (A) with respect to any corporation, 5 percent or more in value of the outstanding stock of such corporation, (B) with respect to a partnership, 5 percent or more interest in the profits or capital of such partnership, and (C) with respect to an estate or trust, 5 percent or more of the beneficial interests in such estate or trust. For purposes of determining a significant ownership interest, an interest owned by or for a corporation, partnership, trust, or estate shall be considered as owned directly both by itself and proportionately by its shareholders, partners, or beneficiaries, as the case may be.