In Nov of 19, I cashed out all of my stocks shares (2266) in an investment account that I have had for roughly 30 years. I have not contributed to the account for over 20 years, it just kept building up on its own. I received a 1099-B which 851 shares were divided into long and short term investments. The remain 1415 shares were not categorized. For the 1415, the 1099-B states "Transactions for which basis is NOT reported to the IRS and for which short-term or long-term determination is unknown. You must determine short or long term gain\(loss) based on your records and report on Form 8949, Part II, with Box E checked, as appropriate. "
1. How do I go back 30 years to check for gains/losses?
2. Do I really even need to check? Will I get into trouble by the IRS if I don't?