You cannot undo a return that has already been filed to add the 1099-R.
You must wait for the IRS to either accept or reject the
return.
If the return has been rejected
by the IRS, then you can add the 1099-R to your return before you resubmit it.
If the return has been accepted
by the IRS, then you will need to file an amended
return to include the additional 1099-R.
The instructions for amending your 2018 return using TurboTax have not yet been released. They will be shown in the article below when they become available.
[edited 1.27.19 | 1:26 pm est]
