@chrisg0 That's only for a single, fully taxable IRA. Read the exceptions carefully, and you'll find that partially taxable IRA's require the gross amount on 4a and the taxable portion on 4b. Also here is the IRS 1040 instruction for multiple distributions:
For IRA's: "If you (or your spouse if filing jointly) received more than one distribution, figure the taxable amount of each distribution and enter the total of the taxable amounts on line 4b. Enter the total amount of those distributions on line 4a." (page 29 of IRS 1040 instructions)
For Pensions: "If you had more than one partially taxable pension or annuity, figure the taxable part of each separately. Enter the total of the taxable parts on Form 1040, line 4b. Enter the total pension or annuity payments received in 2018 on Form 1040, line 4a." (page 31 of IRS 1040 instructions)
