@blizz11 Unfortunately, I didn’t have a whole lot about what I did since I just stepped through the process from TurboTax online.
I had used TurboTax online the previous 2 years (the edition that includes forms for stocks etc) so it allowed me to select that I wanted to amend a previous return so I selected the year I got the letter for and basically followed the screens until I got to the screen showing all possible inputs. I found the place to input my 1099-B and selected to input each sale one by one so I could specify the cost basis and the sale value and the date etc. (I ended up losing $15+ from sale to cover) and adding it automatically updated the forms like the 1040-x etc. I printed the amended return they generated and sent it all in. Though, I have heard conflicting advice on various threads about this - one place said that you might not need to submit a full amended return and just need to send it the supporting documentation. Another place said you need to amend your return and send in everything. I might have erred in the direction of sending too much.
Good luck to you! 👏
