1. If you didn't include the deduction for the contribution on your tax return, your total basis in traditional accounts is $6,500 as of December 31, 2023. Even though you made the contribution in 2024, it was treated as being done for 2023. The conversion would still be treated to have occurred in 2024.
2. The explanation would be that you made a nondeductible contribution after December 31 that wasn't accounted for on your prior 8606.
3. Your 2023 contribution would be nondeductible.
