23 February 1990 T.I. (July 1990 Access Letter, ¶1347)

In the situation where a building was held in joint tenancy by an individual and a corporation owned by him, because no more than 50% of the building was used in the active business of the corporation no part of the value of the corporation's interest in the property would be a qualified use, notwithstanding that the corporation and the individual had a written agreement under which the corporation was entitled to the sole exclusive use and occupation of the portion of the property used in its business.

In a situation where a building was held in joint tenancy by an individual and a corporation which he owned, the entire portion occupied and used by the individual could qualify as his principal residence. The proceeds of disposition of the principal residence portion of the property would be the same proportion of the entire proceeds that the fair market value of the principal residence portion would be of the fair market value of the entire property at the time of disposition.