For what it's worth:
If you own stock that has become worthless because the company went bankrupt and was liquidated, then you can take a total capital loss on the stock.
? However, the IRS wants to know on what basis the value of the stock was determined as zero or worthless. Therefore, you should keep some kind of documentation of the zero value of the stock, as well as documentation of when it became worthless.
Basically, any documentation that shows the impossibility of the stock offering any positive return is sufficient. Acceptable documentation shows the nonexistence of the company, canceled stock certificates, or evidence the stock is no longer traded anywhere. Some companies that go bankrupt allow you to sell them back their stock for a penny. This proves you have no further equity interest in the company and documents what is essentially a total loss.
From Investopedia
