You will have to re-construct the best you can the purchase price of the stock.
You can use historical prices, and need to know if it was purchased at a discount by the employees at that time.
As far as dates go you can use various and then say it is long-term which is anything over one year. This gets more favorable tax treatment.
Here is one link that might help. https://finance.yahoo.com/quote/ge/history/
Also if the stock reinvested the dividends, all of these dividends would be added to the cost of the stock in computing the basis.
If you do not do this, then you would have to enter $0 as cost basis, so depending on the other income you have it might be worthwhile to re-construct this and IRS is pretty good if you use some good sound logic in doing this.
To enter your Investments sold
Click on Federal Taxes
Click on Wages and Income
Click on I'll choose what I work on
Scroll down to Investments
On Stocks, Bonds, Other, click the start or update button
