Sounds like you also have a case of your broker holding "your funds" as collateral. A stock becomes worthless when it falls to zero There is that pesky factual problem that BioAmber never fell to zero. To the contrary. The price skyrocketed just ahead of FINRA suspending the CUSIP. Take it up with your broker. There's nothing BioAmber shareholders can do for you. DO GOVERN YOURSELVES ACCORDINGLY