TurboTax should have tested this very common scenario (partially taxable IRA and fully taxable pension, or vice versa) months ago, noticed the absurd result on line 4a, and sought clarification then. Really, I don't know why someone has to "clarify" for you that line 4a (gross amount) can't be less than line 4b (taxable portion). A sixth grader knows that.
Yes, the IRS instructions are subject to (mis)interpretation, but TurboTax chose the only interpretation that leads to a nonsense result, and is determined to stick with it , despite all the user complaints.
