If you Google "tax aspects of worthless securities" you'll find many detailed references. Note that if you can sell the shares and receive anything in return (beyond the broker's commission), they're not "worthless." Some references suggest obtaining a letter from your broker stating that the securities are worthless.
Here's an IRS reference on the topic:
https://www.irs.gov/faqs/capital-gains-losses-and-sale-of-home/losses-homes-stocks-other-property/lo...).
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
