ira to roth conversion

You will calculate the taxable amount by entering the basis your Traditional IRA accounts as well as the total value of all of your Traditional IRA accounts.  

If you have never made non-deductible contributions to any Traditional IRA accounts that you have, then your basis will be zero.  Non-deductible contributions are essentially after-tax money and that means that it should not be taxed again when you take a distribution from the Traditional IRA.  However, determining the taxable amount is not as simple as just subtracting the basis.  Every distribution from a Traditional IRA is made up of taxable and non-taxable money if there is a basis in any of the accounts.  The taxable amount is proportional to the basis versus the total account values.

So, if there have not been any non-deductible contributions made to your Traditional IRA accounts, then everything is pre-tax money.  This means that the full distribution would be taxable when you take the money out or convert it to a Roth IRA account.

You will enter the basis (total of your non-deductible contributions) of the Traditional IRA in the Deductions and Credits > Retirement and Investments > Traditional and Roth IRA Contributions section of your return.  

As you get started in that section, check the box that you have a Traditional IRA and go through the screens until you see a question about 'any non-deductible contributions' to your IRA.  Check 'yes' and then enter the total basis of the account as of the end of 2023.  Remember, this is only asking for the contributions that were made, not the total value of the IRA.  

(Please respond if this was a 'back door' Roth IRA conversion instead of just a Traditional to Roth conversion.  The answer may be slightly different in that case.)