A Roth conversion moves money from a traditional IRA, where earnings grow tax-deferred and withdrawals are generally taxed as ordinary income, into a Roth IRA, where qualified withdrawals can be tax-free. The trade is simple to state and complicated to execute: the saver pays income tax on the converted amount now in exchange for potential tax-free treatment later. Whether that bargain makes sense depends on facts that differ for every household.
How a Conversion Works
The saver instructs the IRA custodian to move funds, or part of them, from a traditional, SEP or SIMPLE IRA into a Roth IRA. The pre-tax portion of the converted amount is added to taxable income for the year of the conversion. The IRS says the conversion is reported on Form 8606, the same form used to report nondeductible contributions to traditional IRAs and certain distributions.
Unlike direct Roth contributions, conversions are not limited by income. Roth contribution eligibility phases out for 2026 at modified adjusted gross income of $153,000 to $168,000 for single filers and $242,000 to $252,000 for joint filers, according to the IRS, and the contribution limit is $7,500 (or $8,600 for those 50 and older). Those caps do not apply to the amount that can be converted. That feature is why conversions are often discussed alongside high-income planning.
The Tax Bill Is the Price
The converted amount raises income in the conversion year, which can push the saver into a higher tax bracket and may affect other tax items that depend on income. Examples can include the taxation of Social Security benefits, Medicare premium surcharges for higher earners and eligibility for certain credits or health-insurance subsidies. The details vary by situation, so a tax professional can model them.
The usual guidance is to pay the tax from money outside the IRA. Using IRA funds to cover the tax shrinks the amount that moves into the Roth account and, for savers under age 59½, the withheld portion can be treated as an early distribution subject to a 10 percent additional tax.
Conversions made in a year cannot be undone. Since a 2017 law change, a conversion cannot be reversed through recharacterization, so savers should plan with care. Splitting a large conversion over several years is one approach people use to manage the bracket effect.
The Pro-Rata Rule
Savers often assume they can convert only after-tax dollars and skip the tax. The IRS pro-rata rule says otherwise. When a person has both pre-tax and after-tax money in traditional IRAs, a conversion is treated as drawn proportionally from all of their traditional, SEP and SIMPLE IRAs combined.
Here is a hypothetical. A saver has $100,000 across traditional IRAs, including $10,000 of nondeductible contributions that were already taxed. That is 10 percent after-tax money. If the saver converts $20,000, then 10 percent, or $2,000, is nontaxable, and $18,000 is added to income. The conversion cannot be limited to the $10,000 of after-tax money. Form 8606 tracks that after-tax basis year by year, which is why keeping copies matters.
Timing Rules and the Five-Year Clocks
Two five-year rules matter. First, for a Roth IRA's earnings to come out tax-free, the account generally must have been open for at least five years and the owner must be 59½ or older, disabled or otherwise meet the qualifying conditions. Second, each conversion has its own five-year period for the 10 percent additional tax on converted amounts withdrawn early by someone under 59½. IRS publications should be consulted for specifics.
When Conversions Tend to Be Considered
Conversions are most often discussed when:
- Income is temporarily low. A year between jobs, a sabbatical or early retirement before Social Security begins can mean a lower tax bracket than usual.
- Future tax rates may be higher. Tax law can change, and no one knows future rates. The comparison rests on assumptions about both rates and income, not certainty.
- Heirs are a concern. Roth IRAs have no required minimum distributions for the original owner, and heirs may withdraw tax-free if the rules are met, though beneficiaries generally must empty an inherited account within a set period.
- The saver has cash to pay the tax. Without outside money, the math often gets worse.
They are often less appealing when the saver expects a lower bracket in retirement, lacks funds for the tax bill, or would be pushed over a threshold that triggers other costs.
Questions to Settle Before Converting
- What is my marginal rate now, and what do I expect later? The case for converting tends to rest on this comparison.
- Do I have after-tax basis in any traditional IRA? The pro-rata rule applies to the total.
- Where will the tax money come from?
- How long until I need the money? A shorter horizon leaves less time for the tax-free growth to offset the upfront cost.
A conversion is a tax decision as much as an investment one, and many savers talk to a tax professional before acting.
This article is for informational and educational purposes only and should not be considered personalized financial, investment, or tax advice.
