You can deduct worthless stock only in the tax year it becomes
completely worthless. This normally happens when the corporation files
for bankruptcy, stops doing business, and has no assets. Financial
difficulties won't make a company's stock worthless unless there is no
hope that the company will pull through.
Enter a worthless stock like any stock sale but with a sales price of
zero and the word "worthless" in its description. Enter the correct
cost or basis, date acquired, and December 31 as the date sold.
See How do I deduct worthless stock?
https://ttlc.intuit.com/questions/2899549-how-do-i-deduct-worthless-stock
To enter your transaction:
Type in investment sales in the search box,
top right of your screen, then click the magnifying glass
Click the jump
to investment sales link in the search results
Follow to prompts and online instructions