@dmertz I believe the "a" line can be less than "b". If one of the 1099R forms has the same Gross and Taxable amount then it won't show up on 5a.
See IRS 1040 Instructions.
https://www.irs.gov/pub/irs-pdf/i1040gi.pdf
For line 5 page 28 first paragraph middle column……
If your pension or annuity is fully taxable, enter the total pension or annuity payments (from Form(s) 1099-R, box 1) on line 5b; don’t make an entry on line 5a.
