We all know that personal tax is on a cash basis or cash basis, which means that although the money is earned but has not yet arrived, it is not counted as income for the year; the same goes for expenses, if they are not spent, they cannot be counted. Expenses for the current year are used to offset the income for the current year. Although everyone understands the principle, it is still easy to make mistakes in actual operation. Among many investments, stock investment is very common. If you have a lot of stock gains but don’t want to pay more taxes, then the usual principle is to sell some losing stocks before the end of the year, and stocks that cannot be turned around in a short period of time, so that you can use the losses from the sales to offset the losses. Deduct your earnings to achieve the purpose of paying less tax. But under this general principle, there are some restrictions and rules you need to know to avoid unnecessary losses and troubles.