To change the information on this payment, you would have to delete the Form 1099-R and re-enter it in the 1099-R interview. found under Personal > Personal Income > Retirement Plans and Social Security.
See: How
do I delete forms in TurboTax Online?
Why does this happen? Once you enter (or import
or transfer) certain information, the program creates or updates forms and
worksheets that use that information. In many cases, you cannot
"change" that information in the interview process - in a manner of
speaking, it has been "written in ink" on the forms. You have to
delete the form and any associated worksheets in order to correct.
