21.18. The following rules apply for the purpose of determining whether or not a taxpayer is a specified shareholder of a corporation at any time:(a) a taxpayer is deemed to own each share of the capital stock of a corporation owned at that time by a person with whom the taxpayer does not deal at arm’s length;
(b) each beneficiary of a trust is deemed to own that proportion of all the shares of the capital stock of a corporation that are owned by the trust at that time that the fair market value at that time of the beneficial interest of the beneficiary in the trust is of the fair market value at that time of all beneficial interests in the trust;
(c) each member of a partnership is deemed to own that proportion of all the shares of the capital stock of a corporation that are property of the partnership at that time that the fair market value at that time of the member’s interest in the partnership is of the fair market value at that time of the interests of all members in the partnership;
(d) an individual who performs services on behalf of a corporation that would be carrying on a personal services business if the individual or any person related to the individual were at that time a specified shareholder of the corporation is deemed to be a specified shareholder of the corporation at that time if the individual, or any person or partnership with whom the individual does not deal at arm’s length, is, or by virtue of any arrangement, may become, entitled, directly or indirectly, to not less than 10% of the assets or the shares of any class of the capital stock of the corporation or any corporation related thereto; and
(e) notwithstanding paragraph b, where a beneficiary’s share of the income or capital of the trust depends on the exercise by any person of, or the failure by any person to exercise, a power to appoint, the beneficiary is deemed to own each share of the capital stock of a corporation owned at that time by the trust.