Retirement tax questions

You should have entered the nondeductible contribution on your 2023 return and have a 2023 Form 8606 with a basis on line 14 this will be entered into TurboTax when asked if you made  “Any Nondeductible Contributions to Your IRA?” at the end of the retirement interview. This basis will then appear on line 2 of the 2024 Form 8606.

You also need to add your nondeductible traditional IRA contribution for 2024 on your 2024 return:

1. Click on "Search" on the top right and type “IRA contributions” 
2. Click on “Jump to IRA contributions"
3. Select “traditional IRA”
4. Answer “No” to “Is This a Repayment of a Retirement Distribution?”
5. Enter the amount you contributed
6. Answer “No” to the recharacterized question on the “Did You Change Your Mind?” screen
7. Answer the next questions until you get to “Any Nondeductible Contributions to Your IRA?” and select “Yes” if you had a nondeductible contribution before this tax year.
8. Enter your basis in the Traditional IRA from your 2023 Form 8606 line 14 (if you had a basis in the prior year)
9. On the “Choose Not to Deduct IRA Contributions” screen choose “Yes, make part of my IRA contribution nondeductible” and enter the amount (if you have a retirement plan at work and are over the income limit it will be nondeductible automatically and you only get a warning and then a screen saying $0 is deductible).

After this entry TurboTax will enter this nondeductible contribution on line 1 of the 2024 Form 8606.

Please see How do I enter a backdoor Roth IRA conversion? for additional information.