your assumption is incorrect; Turbo Tax is correct . Pension payment flow to line 4a but IRA distributions do not
please see page 29 of the Form 1040 instructions at the link below
at the VERY top on the left of Page 29 it states:
"Except as provided next, leave line 4a blank and enter the total distribution (from Form 1099-R, box 1) on line 4b. The IRA distribution is not included in line 4a per the IRS instructions.
But the pension payment is to be included in line 4a At the very bottom of Page 29 (on the right) and continuing onto page 30, the IRS instructions discuss Pension payments. It's a little convoluted the way it's written as it goes on to state that there are a few exceptions to flowing the Pension Payments to line 4a, but it infers a normal pension payment should be listed on Line 4a - which is exactly how Turbo Tax works.
https://www.irs.gov/pub/irs-pdf/i1040gi.pdf
what is the other error you uncovered? maybe TT was correct there as well?????
