My 1099-B says "basis not reported" but it includes basis as $0.00. This is RSU - so it was also reported in my W2. I can figure out the basis for those shares sold - I can change the basis - but I would like to give some explanation on why I entered that basis - Turbo Tax does not provide an ability to add to the tax form. Is there a way to do this?
There is, but you don't need to. The IRS has a record of the RSU purchase on your W2 so if they decide to review the return they have the basis there.
If you decide to dot the i's and cross the t's you can file the return electronically and then mail form 8453 to the IRS along with your proof of basis. You can add 8453 to your return in TurboTax and print it after you file. But if the IRS has not requested that information I would not bother.
Your employer issued you form 3922. It has the proper stock basis for each transaction. If you do not have the form contact your employer for another copy of it.
IRS says:
"For non-covered securities ( BOX B or E) showing zero (wrong) basis, enter the correct basis yourself.
Use code "B" and put -0- in col (g)."
No explanation is required.
"Is there a way to do this?"
do not try to fix amounts with overrides. That's a no-no.
answer the step-by-step questions about your 1099-B transaction and it will let you enter the correct basis.