In 2024 we did huge Roth conversions which made our AGI too high to make Roth contributions so we did backdoor Roths. My husband had a $100 nondeductible contribution in 2023 so had a basis already, I didn't have a basis. So his 8606 for 2024 had a basis of $98 on line 2, plus his $8000 nondeductible contribution for 2024, and his large (over $100,000) conversion in 2024. His nontaxable portion of the conversion was $97. His new basis was $8001. So in 2025, his 8606 was line 1 = $8000 nondeductible contribution for 2025 made in 2025, line 2 = $8001 basis from line 14 of the 2024 form, line 3 total = $16001 sum of those two, line 5 is the same since he didn't make any contributions for 2025 in 2026. Line 6 is blank even though I entered 0.00 because he didn't have a balance in his traditional IRA on 12/31/2025. Line 7 is blank (though it should be 0) since you don't enter Roth conversions there, only "regular" distributions from traditional IRAs. Lines 11 and 12 are also blank (but would be 0 if filled in). So line 13 is $8004 (his $8000 nondeductible contribution plus $4 in interest he converted) nontaxable distribution (conversion). I'm not sure how that was done since line 13 is supposed to be the sum of lines 11 and 12 (nontaxable portion NOT converted to Roth). I get that the $8000 nondeductible "backdoor" contribution shouldn't be taxed, but I don't quite get why the $4 interest wasn't taxed. But subtracting $8004 from $16,001 his new basis on line 14 is $7997. Is this correct? I did get the popup message that he couldn't deduct his IRA contribution.
