Roth Conversions
Understand conversion timing, taxes, future RMDs, Medicare premiums, and survivor planning.
Managing Lifetime Taxes and Building Tax-Free Retirement Savings
Why Roth conversions matter in retirement planning
A Roth conversion moves money from a traditional IRA or another eligible pretax retirement account into a Roth IRA. The amount converted is generally included in taxable income for that year. In exchange, future qualified Roth IRA withdrawals are generally free from federal income tax. Roth IRAs also have no lifetime required minimum distributions for their original owners.
The real decision is not simply whether to pay tax now or later. It is how much tax to pay, when to pay it, where the tax money comes from, and what happens to the rest of the retirement plan. A conversion can change future required withdrawals, Medicare premiums, Social Security taxation, investment growth, and what a surviving spouse or heir receives.
A conversion is not automatically a tax-saving move. Sometimes paying taxes early improves long-term after-tax wealth. Other times it reduces the money left for retirement. The answer depends on the whole household.
How a conversion works
Suppose you transfer $50,000 from a fully pretax traditional IRA into a Roth IRA. You generally add $50,000 to your taxable income for the conversion year. The amount moved is not a second cash payment to you. It remains invested, now in a different type of account. Future earnings can qualify for tax-free treatment if the rules are met.
If you are already subject to RMDs, you must take that year’s required distribution before converting additional IRA funds. An RMD itself cannot be converted. A direct trustee-to-trustee conversion can avoid unnecessary handling of the money, but it does not remove the conversion tax.
Traditional IRAs with nondeductible contributions need special care. The IRS generally applies a pro rata calculation across traditional, SEP, and SIMPLE IRAs when determining the taxable part of a conversion. You cannot simply choose to convert only the after-tax dollars from one mixed IRA. Form 8606 is often needed.
The tax bracket question: what does the conversion actually cost?
A conversion adds to ordinary income. That income can fill the rest of one tax bracket and then spill into the next. The relevant cost is the additional total tax caused by the conversion, not simply your current marginal tax rate.
Consider a retiree with $70,000 of taxable income before converting. Assume, only for this illustration, that the next $30,000 would be taxed at 12% and income above that amount at 22%. A $50,000 conversion would produce:
| Portion of conversion | Illustrative rate | Additional federal tax |
|---|---|---|
| First $30,000 | 12% | $3,600 |
| Next $20,000 | 22% | $4,400 |
| Total $50,000 | Blended 16% | $8,000 |
These are invented bracket boundaries for teaching the calculation, not the actual federal brackets for a particular year. Real tax costs also depend on deductions, filing status, capital gains, state taxes, and other income. Some conversions may affect tax credits or deductions.
It is often more useful to compare several conversion sizes than to assume that one large conversion is best. A smaller conversion may use a lower bracket; a larger one may reduce more future RMDs but create a higher tax bill today.
Why paying the conversion tax from outside the IRA matters
Imagine converting $100,000 while facing a 22% additional tax cost. The estimated tax is $22,000. If $22,000 is paid from a taxable savings account, the full $100,000 can move into the Roth IRA. If tax is withheld from the IRA distribution instead, less may reach the Roth account, and the withheld amount can have additional consequences. For someone under age 59½, amounts not converted may also face an early-distribution penalty unless an exception applies.
Using outside cash is not automatically better. That cash might otherwise have earned returns, and selling taxable investments to pay the bill may create capital gains taxes. A sound comparison tracks both accounts, the tax payment, and their growth over time.
Why conversion timing can matter more than conversion size
Many people have a period after leaving work but before Social Security and RMDs begin. Their taxable income may be lower during these years. That can create room for conversions at rates below those they might face later. However, a pension, part-time work, investment gains, or a spouse’s earnings may reduce that room.
Consider someone retiring at 65 who expects RMDs at 75. Rather than converting $400,000 in one year, the person might compare $40,000 each year for ten years with larger conversions in fewer years. The smaller annual conversions may limit bracket increases, but future investment growth and changing tax laws can alter the result. These are strategy choices, not equal outcomes.
A conversion during a market decline can move more shares into the Roth for the same taxable dollar amount. If those investments recover, more future growth may occur inside the Roth. But the market may fall further, and the conversion tax is still owed. A conversion is not a prediction that the market will recover.
The effect on future RMDs
A Roth conversion reduces the pretax balance that would otherwise be used to calculate future RMDs. It can also reduce later taxable distributions, especially when done years before RMDs start. The benefit is not equal to the amount converted, because investment growth and later withdrawals change both accounts.
For a simple illustration, assume a $200,000 conversion takes place ten years before RMDs begin. At an assumed 6% annual return, that amount would grow to about $358,170 after ten years if left untouched. Moving it to a Roth means that projected amount would no longer be part of the traditional IRA balance used for the owner’s RMD calculation. It would still be part of the person’s total retirement savings.
Using an illustrative age-75 divisor of 24.6, $358,170 of traditional IRA value would generate about $14,560 of first-year RMD, before considering the rest of the IRA. The Roth IRA generally would not require an owner RMD. This does not mean $14,560 in tax savings. It means less forced taxable distribution, with any tax benefit depending on the person’s income and tax rate.
Social Security taxes: a hidden cost of conversions
For federal tax purposes, provisional income generally includes adjusted gross income, tax-exempt interest, and half of Social Security benefits, with certain adjustments. Depending on filing status and income, up to 85% of Social Security benefits may be taxable. That does not mean the benefits are taxed at an 85% tax rate.
A conversion may cause more Social Security benefits to become taxable if the household has not already reached the maximum taxable portion. For example, an additional $10,000 conversion can sometimes increase taxable income by more than $10,000 because part of the Social Security benefit also becomes taxable. The actual increase must be calculated for the household.
The opposite can happen later: reducing future pretax withdrawals and RMDs may help keep Social Security taxation lower in some years. Whether the early tax cost is worth the later benefit requires a multi-year comparison.
Medicare premiums: the two-year lookback
Medicare uses income-related monthly adjustment amounts, or IRMAA, to increase Part B and Part D premiums for people above certain income thresholds. The calculation generally uses modified adjusted gross income from a tax return two years earlier. For example, a conversion reported on a 2026 return may affect Medicare premiums in 2028.
This creates a planning tradeoff. A larger conversion may increase Medicare premiums for one or more years, but could reduce later RMDs, taxes, or future premium exposure. The additional premium is a real cost and belongs in the comparison. IRMAA brackets and premium amounts change over time, so a plan should use the correct year’s figures.
Certain life-changing events, including the death of a spouse or work stoppage, may support a request for an IRMAA adjustment. A Roth conversion itself is generally not one of the qualifying events.
Surviving-spouse planning: when the tax picture changes
For many couples, the tax risk becomes greater after the first spouse dies. The survivor may lose one Social Security payment and some pension income, yet many household expenses remain. In later tax years, the survivor generally files as single unless another filing status applies. The single tax brackets and standard deduction may create a higher tax burden on remaining income.
Suppose a couple has $120,000 in combined annual income and later the survivor has $90,000. The survivor’s tax bill does not necessarily fall in proportion to income because filing status, deductions, the taxable share of Social Security, and RMDs can change. A large pretax IRA can create unwanted taxable income precisely when the survivor has fewer tax advantages.
Converting some pretax savings while both spouses are alive may reduce future RMDs and give the survivor more access to qualified tax-free Roth withdrawals. But it can also raise joint taxes today. The best result depends on both spouses’ ages, health, income sources, expected spending, and the tax cost in each period.
Inheritance: what heirs may receive
Traditional IRA distributions to heirs are generally taxable as ordinary income, except for any basis or special rules. Many non-spouse beneficiaries must empty inherited retirement accounts within ten years, and some must also take distributions during that period. This can concentrate taxable income in the heirs’ working years.
Inherited Roth IRAs are also subject to beneficiary distribution rules, including a ten-year rule for many non-spouse heirs, but qualified distributions are generally tax-free. A Roth conversion may therefore shift some future income-tax burden away from heirs. It does not eliminate estate taxes, guarantee future tax rules, or make every inherited Roth distribution automatically qualified.
The right comparison includes the taxes paid on conversion, the amount available to the owner during retirement, and the after-tax value the heirs may receive. A larger Roth inheritance can be attractive even when the owner’s own ending value changes only slightly.
Investment returns, account mix, and after-tax ending wealth
Two plans can use the same starting market assumptions and still develop different overall returns as money moves between account types and investments. A more conservative mix might produce less growth but reduce risk. A more aggressive mix might produce more projected growth with larger possible losses. A conversion does not, by itself, create investment returns.
To compare strategies fairly, measure all accounts after the estimated taxes that would apply at the planning horizon. A $1 million pretax IRA and a $1 million qualified Roth IRA are not the same amount of spendable wealth. Likewise, lower lifetime taxes do not automatically mean greater after-tax ending wealth if taxes were paid earlier and money had less time to grow.
When conversions may be less helpful
Conversions may be unattractive when today’s tax rate is much higher than the rate expected on later withdrawals, when the conversion would trigger large Medicare premium increases, when tax payments would strain cash reserves, or when the owner expects to give substantial traditional IRA assets to charity. Converting just to reduce RMDs can be a mistake if the lifetime cost is greater than the benefit.
Qualified charitable distributions can be particularly useful for eligible IRA owners who already give to charity. A QCD may satisfy all or part of an RMD while keeping the eligible distribution out of adjusted gross income. Converting the same money first could create avoidable taxable income. The rules and annual limits must be checked for the applicable year.
People planning to move between states should also consider state income taxes. A conversion before moving from a high-tax state to a no-income-tax state may cost more than waiting, while the reverse move may favor an earlier conversion. Residency and sourcing rules can be complex.
A practical way to compare Roth conversion strategies
Start with a year-by-year estimate of wages, pensions, Social Security, taxable investment income, spending needs, account balances, and RMDs. Then compare a no-conversion plan with several conversion schedules. For each year, calculate federal and state taxes, the taxable portion of Social Security, Medicare premiums when applicable, and the source of money used to pay the taxes.
Continue the projection through the full retirement period and, for married households, include a surviving-spouse period. Look at lifetime taxes, total RMDs, Roth balances, the ability to meet spending needs, and net-of-tax ending value. Also test less favorable market returns or higher spending, because a strategy that looks best under one set of assumptions may not remain best when circumstances change.
Most important, separate a household’s priorities. Some retirees want the highest projected after-tax wealth. Others value more tax-free income, lower forced distributions, or greater flexibility for a spouse or heirs. Those goals may point to different strategies.
Common questions about Roth conversions
Is a Roth conversion the same as a Roth contribution?
No. A conversion moves eligible existing retirement money into a Roth account. It is not limited by the annual Roth IRA contribution cap, but it may create taxable income.
Can I convert after age 73 or 75?
Yes. You can generally convert after RMDs begin, but you must first satisfy that year’s RMD. The RMD amount cannot be converted.
Can I undo a conversion if the market falls?
Generally no. Roth conversions made under current rules cannot be recharacterized back into traditional IRAs.
Do I have to wait five years to use converted money?
Roth IRA distributions have ordering and five-year rules. Each taxable conversion may have its own five-year period for the 10% early-distribution penalty if you are under age 59½, while qualified earnings withdrawals have separate requirements. The exact rule depends on age and distribution type.
Will a conversion always lower future taxes?
No. It may increase taxes today and lower them later, but the net result depends on tax rates, investment growth, withdrawals, and the planning period.
Should I convert my entire IRA?
Not automatically. Large conversions can push income into higher brackets and raise Medicare costs. A series of smaller conversions may be better, but only a comparison can establish that.
Does a Roth conversion protect me from every future tax change?
No. Qualified Roth distributions receive favorable treatment under current law, which can reduce exposure to future ordinary income-tax increases. Congress can change tax rules.
Final perspective
Roth conversions are a tool, not a goal by themselves. The best plan is the one that balances today’s conversion tax against future spending needs, forced distributions, Medicare costs, investment risk, and the financial security of a surviving spouse or heirs. A well-timed conversion can create meaningful flexibility. A poorly timed conversion can use money that would have served retirement better elsewhere.
Educational illustration only. Tax laws, Medicare thresholds, and beneficiary rules can change. The examples are not personalized tax or investment advice.