What I mean but "performs the calculation correctly" is that 2024 TurboTax accurately performs the calculations on TurboTax's Roth IRA Contribution Limit Worksheet as specified by the IRS on Worksheet 2-2 of the 2024 IRS Pub 590-A. TurboTax's worksheet will also show on line 1 the MAGI that TurboTax has calculated using the method described by Worksheet 2-1 of IRS Pub 590-A.
If you are filing Single or Head of Household (or Married Filing Separately and you did not live with your spouse at any time during the year), the contribution limit declines from the full annual amount at an MAGI of $146,0000 to zero at $161,000. $158,000 is $3,000 below $161,000, so that means that the contribution limit at an MAGI of $158,000 would be 3,000/15,000 or 20% of the unlimited amount for your age. If you are under age 50, that would mean a maximum Roth IRA contribution of $1,400. This is exactly the result that TurboTax produces.
However, to be eligible to contribute that $1,400 you also need to have at least $1,400 of compensation to support the contribution. The amount of compensation available to support the contribution will also be shown on the Roth IRA Contribution Limit Worksheet.
