Pre-tax IRA to Back door Roth; any post tax IRA to Roth possible?

[lkjr]

Hello 

I performed a Roth conversion earlier this year, converting a 100% pretax IRA to a Roth (knowing that I'll pay income tax on the full pre-tax amount).

I'm wondering now that my pre-tax IRA balance is at 0 if I could do in the same year a non-deductible contribution to the IRA and convert it to my Roth account - or if it's better to keep the IRA clean the year of the conversion and postpone the backdoor Roth to 2026. 

[baldietax]

Check form 8606 and try filling it out for your situation from 2025 filing perspective to get comfortable with the process - the calculation for the tax on the Roth conversion is based on the ending balance of the IRA as of 12/31/2025 (line 6) - as long as that is zero at year-end and you do not have any remaining basis in the IRA at the end of the year, then you should be able to do a backdoor Roth also.

Line 9 in the tax calc will be your total conversion from Line 8, since Line 6 is zero; lines 10/11 divide and multiply your nondeductible by the total conversion, so Line 11 ends with your nondeductible as the nontaxable amount on the conversion.

You never pay tax on any after tax / nodeductible money (= basis) that you contributed to the IRA when converting to a Roth, only the earnings and pre-tax contributions are taxable, it's just a question of timing when that money is considered part of conversion which is a pro rata mix of taxable and nontaxable contributions at the time; so if you empty out the IRA then you are fully converting the nondeductible contribution and won't pay tax on that portion.

[baldietax]

PS just make sure you are eligible for the IRA contribution - the MAGI/contribution limits are well known but also you can only contribute if you have earned income for the amount of the contribution, some folks don't realize til filing and Turbotax delivers the bad news it wasn't a valid contribution, then it gets messy.

https://www.fidelity.com/learning-center/smart-money/ira-contribution-limits

You also cannot contribute more to your IRAs than the income you earn each year. If your income is lower than the contribution limit, your annual IRA contribution may be limited to your earned income. For example, if your earned income is $5,000, your max contribution limit is $5,000.

[dmertz]

There is no tax benefit to using a second Roth IRA to receive another Roth conversion.  The result will be the same if you do an additional Roth conversion to the same Roth IRA or to a different Roth IRA.  I other words, there is no benefit to keeping the first Roth IRA "clean."

There used to be a small potential benefit to using a different Roth IRA back when recharacterization of Roth conversions were permitted.  Using a separate Roth IRA could make the calculation of net attributable income easier.  However, the tax code was changed for 2018 and beyond such that recharacterizations of Roth conversions are no longer permitted.