Capital Loss
Also called: realised loss, investment loss
A capital loss is selling an asset for less than you paid — the mirror image of a capital gain, and in most tax systems a useful one. Losses offset gains first, then a limited amount of ordinary income, and the unused remainder usually carries forward indefinitely. That makes a loss a real, storable asset rather than merely a mistake. The rule that constrains it is the wash-sale rule, which disallows the deduction if you buy back a substantially identical security too quickly.