I mistakenly contributed after-tax money to a traditional IRA in 2025. What are the options?

You can convert the funds anytime. You can convert the rest of the funds now. The conversion happened in 2025. Therefore, the conversion will be reported next year on your 2025 return when you receive the 2025 Form 1099-R for the conversion.

This year, on your 2024 return, you will enter the nondeductible traditional IRA contribution for 2024:

1. Login to your TurboTax Account 
2. Click on "Search" on the top right and type “IRA contributions” 
3. Click on “Jump to IRA contributions"
4. Select “traditional IRA”
5. Answer “No” to “Is This a Repayment of a Retirement Distribution?”
6. Enter the amount you contributed
7. Answer “No” to the recharacterized question on the “Did You Change Your Mind?” screen
8. 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.
9. Enter your basis in the Traditional IRA from your 2023 Form 8606 line 14 (if you had a basis in the prior year)
10. 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).

TurboTax will create Form 8606 with a basis on line 14 and this will be carried forward to your 2025 return.

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