Examine Form 8690 to see the calculation of the amount (line 21) that is to be included in on Schedule 3 line 11 and on Form 1040 line 18d. Is the amount on Form 8690 line 21 not appearing on Form 1040 line 18d? (With online TurboTax you'll need to download the pdf of your tax return to see this form.)
Are you subject to Net Investment Tax on Form 8960 and failing to factor that into you own calculations?
Are you subject to additional Medicare tax on Form 8959 and failing to factor that into you own calculations?
