preacquisition loss
(3) Preacquisition loss (A) In general The term “preacquisition loss” means— (i) any net operating loss carryforward to the taxable year in which the acquisition date occurs, and (ii) any net operating loss for the taxable year in which the acquisition date occurs to the extent such loss is allocable to the period in such year on or before the acquisition date. Except as provided in regulations, the net operating loss shall, for purposes of clause (ii), be allocated ratably to each day in the year. (B) Treatment of recognized built-in loss In the case of a corporation with a net unrealized built-in loss, the term “preacquisition loss” includes any recognized built-in loss.