You can only write off a stock as worthless in the year it became worthles (on 12/31 of the year), if you don't do it in the year it became worthless, you must file an amended return for that year. So it is very important to determine the year that a stock became worthless. I would think the IRS has a database that identifies the year so they can cross check returns.

Circuit City is still in business, so the stock may not be "worthless" according to the IRS.

See this similar thread here on this site:
https://www.askmehelpdesk.com/taxes/circuit-city-stock-320736.html

Just to clarify, Circuit City is no longer in business, but their name was bought by Systemax who is continuing to use it for a WEB presence.