Is there any reference about this requirement? Short-term loss should be offset by short-term gain, and long-term loss should be offset by long-term gain. And some losses are not allowed to offset due to wash sale. The determination of wash sale can be tricky -- some brokers only report the wash sale of exactly the same security. What if one did not offset the short-term loss in the previous tax year? Does she need to revise the last year's tax document, or carry it over to the next tax year and offset with that year's short-term gain?
