26 U.S.C. § 860D — REMIC defined

(a) General rule. “Real estate mortgage investment conduit” and “REMIC” mean an entity: (1) to which a REMIC election applies for this and all earlier tax years; (2) whose interests are all regular or residual interests; (3) with exactly one residual-interest class, with pro-rata distributions; (4) whose assets, at the end of the third month after startup day^* and afterward, are substantially all qualified mortgages and permitted investments^*; (5) whose tax year is the calendar year; and (6) with reasonable arrangements to ensure (A) residual interests are not held by disqualified organizations, as defined in section 860E(e)(5), and (B) the entity provides information needed to apply section 860E(e). During a qualified liquidation^*, paragraph (4) does not apply during the liquidation period^*. (b) Election. (1) An otherwise qualifying entity may elect REMIC treatment for its first tax year by making the election on that year's return. It applies to that year and later years unless paragraph (2) applies. (2)(A) If the entity stops being a REMIC during a tax year, it is not a REMIC for that year or later years. (B) A termination is disregarded, and the entity continues as a REMIC or is treated in another way the Secretary^* finds appropriate, if (i) it stopped being a REMIC, (ii) the Secretary finds the stop was inadvertent, (iii) reasonable corrective steps are taken promptly after discovery, and (iv) the entity and every person who held an interest during the period agree to adjustments the Secretary requires, consistent with treating the entity as a REMIC or as a C corporation^*.