The 1040 Worksheets keeps IRA and pension distributions separate. The line labeled "4b" is the taxable pensions as in prior years' line 16b. The Form 1040 line 4b is combined IRA + pensions and is equal to the 1040 Worksheet's amount on the line under IRA distributions, Taxable amount (above line "4b") plus the taxable pensions on line "4b". That's a little confusing when you're trying to match up and the 1040 Worksheet could do better labeling I think.