I spoke with the IRS today and this is what I was told regarding a worthless security. A stock that's in serious enough trouble will fail to meet the requirements for trading on a stock exchange. It will be delisted, which means you can no longer sell these shares in a normal transaction. For a period of time, though, it's likely that speculators will be willing to purchase shares at some dirt-cheap price, hoping they'll end up having at least a little value. Bids for these shares may be available through the pink sheets, like SLJB. As a result, your shares are not completely worthless. They're just nearly worthless. You can't claim the loss until it finally becomes clear that the value of the shares has fallen all the way to zero. Again, if there's any chance that securities could have a value, they're not worthless.