My big thanks to all of you!
Here is a little bit background about my questions. The cost basis reported to me by my broker (with box E checked) is different from what I calculated. It may be caused to multiple purchases and sells of the same stock in the past several years. So, I think I need to make a correction on my tax return. But then, if IRS sees that the cost basis on my tax return is different from that showing on 1099-B (although box E is checked, IRS still knows the cost basis showing on the SAME1099-B sent to both it and me, right?), would IRS ask me to provide the evidence? If so, I would need to go back a few years. The difference is only few hundred $. I am not sure if it worth the trouble if the IRS does ask me to provide the details.
