11662: 1099-DIV - Box 9

See Pub. 550, Investment Income and Expenses (Including Capital Gains and Losses):

"Liquidating Distributions
Liquidating distributions, sometimes called liquidating dividends, are distributions you receive during a partial or complete liquidation of a corporation. These distributions are, at least in part, one form of a return of capital. They may be paid in one or more installments. You will receive Form 1099-DIV from the corporation showing you the amount of the liquidating distribution in box 9 or 10.

Any liquidating distribution you receive is not taxable to you until you have recovered the basis of your stock. After the basis of your stock has been reduced to zero, you must report the liquidating distribution as a capital gain. Whether you report the gain as a long-term or short-term capital gain depends on how long you have held the stock.

Distributions less than basis. If the total liquidating distributions you receive are less than the basis of your stock, you may have a capital loss. You can report a capital loss only after you have received the final distribution in liquidation that results in the redemption or cancellation of the stock. Whether you report the loss as a long-term or short-term capital loss depends on how long you held the stock."

Report capital gains and losses on Form 8949.