1099-B uncovered stock sale with unknown purchase date

[jdbuck]

I have shares of stock gifted to me by my father in 2012.  I have a bases for all shares except purchases prior to 2011.  My father has since passed and I have no record to establish a basis now that I have sold them in 2024.  Can I select a stock price at the end of 2010 and use that for the bases for the uncovered shares?

[DavidD66]

No, you can't just select an arbitrary date the corresponding price.  You have to have some reasonable basis for selecting a date and the corresponding price for the stock.  For example, if you know the stock was purchased in 2010, you could use the lowest price that the stock traded at during 2010.  If you can't determine a date or a period, you could use the historical low price for the stock.  If you can't come up with some reasonable basis to determine a cost, you will have to use $0.00 as your cost basis.