A capital loss is a loss on the sale of a capital asset such as a stock, bond, mutual fund or investment real estate. As with capital gains, capital losses are divided by the calendar into short- and long-term losses.
Can I deduct my capital losses?
Yes, but there are limits. Losses on your investments are first used to offset capital gainsof the same type. So, short-term losses are first deducted against short-term gains, and long-term losses are deducted against long-term gains. Net losses of either type can then be deducted against the other kind of gain.也就是说，如果short/long term都是gain, 那么他们的税率是不同的。但是，如果short term是loss，那么它可以和long term 一起计算。
过去留下的损失也可以一起处理。
https://turbotax.intuit.com/tax-tips/investments-and-taxes/capital-gains-and-losses/L7GF1ouP8
