may be made under this section with respect to any qualified stock if— (i) the qualified employee has made an election under subsection (b) with respect to such qualified stock, (ii) any stock of the corporation which issued the qualified stock is readily tradable on an established securities market (as determined under paragraph (1)(B)(iii)) at any time before the election is made, or (iii) such corporation purchased any of its outstanding stock in the calendar year preceding the calendar year which includes the first date the rights of the employee in such stock are transferable or are not subject to a substantial risk of forfeiture, unless— (I) not less than 25 percent of the total dollar amount of the stock so purchased is deferral stock, and (II) the determination of which individuals from whom deferral stock is purchased is made on a reasonable basis. (C) Definitions and special rules related to limitation on stock redemptions (i) Deferral stock For purposes of this paragraph, the term deferral stock means stock with respect to which an election is in effect under this subsection. (ii) Deferral stock with respect to any individual not taken into account if individual holds deferral stock with longer deferral period Stock purchased by a corporation from any individual shall not be treated as deferral stock for purposes of subparagraph (B)(iii) if such individual (immediately after such purchase) holds any deferral stock with respect to which an election has been in effect under this subsection for a longer period than the election with respect to the stock so purchased. (iii) Purchase of all outstanding deferral stock The requirements of subclauses (I) and (II) of subparagraph (B)(iii) shall be treated as met if the stock so purchased includes all of the corporation’s outstanding deferral stock. (iv) Reporting Any corporation which has outstanding deferral stock as of the beginning of any calendar year and which purchases any of its outstanding stock during such calendar year shall include on its return of