Brokerage statements do not always report the sales category, even if the information is available on the 1099-B.
If you held the security less than one year, use code B (short-term, non covered)
If you held the security more than one year, use code E (long-term, non covered)
The IRS is receiving the 1099-B information from the broker, but is relying on you to report the correct category (and cost basis, in some cases)
As for documentation, save any supporting information that you have, such as trade confirmations, screenshots of historical prices from finance.yahoo.com, etc.
Input your 1099-B at:
Federal Taxes > Wages & Income >
Scroll down to Investment Income, then click Show More
Select Start next to Stocks, Mutual Funds, Bonds, Other
