How to Navigate the Tax Impact of Roth IRA Conversions

The tax impact of Roth IRA conversions comes down to one rule: the amount you move from a traditional IRA or 401(k) into a Roth is added to your taxable income that year and taxed as ordinary income. This guide explains how it stacks on your other income, the hidden costs most savers miss (Medicare, Social Security, and state tax), and the timing levers that lower the bill.

Last reviewed: August 2026 | Written and reviewed by Craig Wear, CFP®, founder of Q3 Advisors

What is a Roth IRA conversion (and how is it different from a contribution)?

A Roth IRA conversion moves money from a pre-tax traditional IRA or 401(k) into a Roth IRA, where it grows and later comes out tax-free. A conversion is not a contribution: contributions are capped ($7,500 in 2026, or $8,600 at age 50 and older) and phased out at higher incomes, while a conversion has no dollar limit and no income limit. The trade-off is that the converted amount is taxable now.

A contribution uses dollars you have already been taxed on and is capped by the 2026 phase-out ($153,000 to $168,000 of income for single filers, $242,000 to $252,000 for married couples filing jointly). A conversion instead takes dollars that were never taxed and pays the tax now so they never get taxed again, with no income ceiling. Our guide on how much to convert to a Roth walks through the math, and the Q3 Advisors Roth conversion service page covers the mechanics.

How are Roth conversions taxed?

The converted amount is taxed as ordinary income in the conversion year, not at the lower long-term capital-gains rates. The IRS treats it like a withdrawal you did not spend: your custodian reports it on Form 1099-R, and it lands on your Form 1040 as taxable income. There is no separate conversion tax rate; it is simply added to everything else you earn that year.

Gains inside the account get no capital-gains treatment: a $100,000 conversion is $100,000 of ordinary income. You also cannot convert a required minimum distribution (RMD): at RMD-age you must take the RMD first, and only dollars beyond it can be converted.

Do Roth conversions count as income? (the AGI and MAGI ripple effect)

Yes. A Roth conversion counts as income and increases both your AGI and your modified adjusted gross income (MAGI) for the year. That single change ripples through the tax code: MAGI is the figure used to set Medicare premiums, to calculate how much of your Social Security is taxable, and to determine whether the 3.8% Net Investment Income Tax applies.

The conversion itself is not net investment income, so it is not directly hit by the 3.8% Net Investment Income Tax (NIIT). It can still trigger the NIIT by lifting MAGI above the 2026 thresholds of $200,000 (single) or $250,000 (married filing jointly), which then taxes your other investment income, as our explainer on the Net Investment Income Tax in 2026 details.

What tax bracket will my conversion land in?

Your conversion stacks on top of your other taxable income, so it fills your current bracket first and then spills into higher ones. The 2026 federal brackets run from 10% to 37%, and the One Big Beautiful Bill Act (P.L. 119-21, OBBBA) made these rates permanent, removing the old 2025 sunset. A conversion can straddle two or three brackets in a single year.

Source: IRS Revenue Procedure 2025-32. The 2026 standard deduction is $16,100 (single) and $32,200 (married filing jointly), with a temporary senior deduction of $6,000 per person age 65 and older through 2028. Because OBBBA locked in these brackets, the old urgency to convert before a scheduled rate increase has faded, which makes the year-by-year planning in our Roth conversion break-even analysis more useful than rushing a deadline.

How much tax will I actually pay? A worked example

Because a conversion stacks on your existing income, the effective rate is usually lower than your top bracket. A retired couple with $50,000 of taxable income who converts $90,000 fills the 12% bracket first, and only the portion above $100,800 reaches 22%, producing a blended rate near 16%.

Consider a married couple, both 66, filing jointly, with $50,000 of taxable income after deductions. They convert $90,000, raising taxable income to $140,000. Here is how that conversion is taxed:

The $90,000 conversion adds about $14,720 of federal tax, an effective rate near 16.4%, even though part is taxed at 22%. Filling a lower bracket, rather than converting one lump that spills into 32% or 35%, is a common goal. State tax and the hidden costs below add to this bill.

The hidden tax impacts most people miss

The income tax on the conversion is only the visible cost. Because a conversion raises your MAGI, it can also increase your Medicare Part B and Part D premiums two years later, subject more of your Social Security to tax, and add state income tax. These second-order effects can raise your true marginal rate above your federal bracket, sometimes past 40%.

Will a Roth conversion raise my Medicare premiums? (the IRMAA two-year lookback)

It can. Medicare uses a MAGI-based surcharge called IRMAA (the Income-Related Monthly Adjustment Amount), and it looks back two years. A conversion in 2026 that pushes MAGI above $109,000 (single) or $218,000 (married filing jointly) can raise your 2028 Medicare Part B and Part D premiums. The standard 2026 Part B premium is $202.90 per month, and IRMAA adds a surcharge on top of it.

The two-year lookback is the trap: because 2026 income sets 2028 premiums, a large conversion at 63 or 64 can inflate premiums right as you enroll at 65. The last conversion year that never affects a premium is the year you turn 62. IRMAA is also a cliff: crossing a threshold by one dollar moves you to the next surcharge tier for the whole year, so many investors convert to just below a threshold.

How does a conversion affect my Social Security taxes? (the tax torpedo)

A conversion raises your provisional income, the figure that decides how much of your Social Security benefit is taxable. As it climbs, up to 85% of your benefit becomes taxable. When each extra dollar of conversion also makes 85 cents of Social Security taxable, your effective marginal rate on that dollar can reach about 40.7% (a 22% bracket times 1.85), a spike often called the tax torpedo.

Will I owe state taxes on the conversion?

Usually, yes. Most states treat a Roth conversion as taxable income in the year you convert, based on where you live that year. Nine states levy no personal income tax at all (Alaska, Florida, Nevada, New Hampshire, South Dakota, Tennessee, Texas, Washington, and Wyoming), so a resident of those states owes no state tax on a conversion. Residents elsewhere should add their state rate to the federal cost.

Residency in the conversion year is what matters, not where you earned the money. Some retirees time larger conversions after establishing residency in a no-tax state. State rules vary, so confirm your own.

How do I minimize the tax impact of a Roth conversion?

The main levers are paying the tax from outside the IRA, spreading conversions across low-income years, and staying inside a target bracket. Each controls how much of the conversion is taxed and at what rate. Because conversions are irreversible (the 2017 Tax Cuts and Jobs Act eliminated recharacterization starting in 2018), sizing them correctly before you convert matters.

Pay the tax from outside your IRA (and the under-59.5 trap)

Pay the conversion tax from a taxable brokerage or savings account, not from the IRA itself. Using outside funds lets the full converted balance keep growing tax-free. If you are under 59.5 and have tax withheld from the IRA (or use IRA dollars to pay the bill), the IRS treats that withheld amount as a separate early distribution: it is taxable and hit with a 10% penalty.

An investor under 59.5 who converts $100,000 and has the custodian withhold $22,000 for taxes has taken a $22,000 early distribution: it owes tax plus a $2,200 penalty, and only $78,000 lands in the Roth. Paying that tax from a checking account avoids the penalty and moves the full $100,000 across.

Convert in low-income years (after retirement, before RMDs and Social Security)

The lowest-cost window for many retirees is the gap between leaving work and starting RMDs and Social Security. In those years, taxable income is often low, so a conversion can fill the 10%, 12%, or 22% bracket at a modest rate. RMDs begin at age 73, or age 75 for those born in 1960 or later (the earliest age-75 RMD year is 2035), which sets how long this window lasts.

Converting during these years does double duty: it is taxed at a lower rate now, and it shrinks the balance that would otherwise drive up RMDs later. Note the deadline: a conversion counts in the year it is completed, so the cutoff is December 31, not the April tax-filing date, as our 2026 Roth conversion deadline guide explains.

Watch the pro-rata rule and the five-year clock

If you hold any after-tax (nondeductible) basis in a traditional IRA, the pro-rata rule applies: the IRS aggregates all your traditional IRA balances and taxes each conversion in proportion to the pre-tax share. You cannot convert only the after-tax dollars. Separately, each conversion starts its own five-year clock, and Form 8606 tracks your basis.

If 90% of your combined traditional IRA balances are pre-tax, then 90% of any conversion is taxable regardless of which dollars you move. The five-year clock matters mainly before age 59.5: withdrawing converted principal within five years and before 59.5 can trigger the 10% penalty. After 59.5, that penalty rule no longer applies.

When a Roth conversion is NOT worth it

A conversion often does not pay off when you expect a lower tax bracket in the future than today, when you would have to pay the tax from the IRA itself, or when the extra income would spike Medicare IRMAA or the taxation of your Social Security. Charitably inclined retirees also frequently find that other tools serve them better.

• You expect a lower bracket later, so paying tax now at a higher rate loses money.
• You have no outside funds and would pay the tax from the IRA, shrinking it and risking penalties under 59.5.
• The added income would cross an IRMAA threshold or trigger the Social Security tax torpedo with no offsetting benefit.
• You plan to give to charity: a Qualified Charitable Distribution (QCD), available from an IRA (not directly from a 401(k)) at age 70.5, moves IRA dollars out tax-free instead.
• Your heirs are in a lower bracket than you, so leaving them pre-tax dollars may cost less overall.

How this reduces future RMDs and taxes for your heirs

Every dollar you convert leaves your traditional IRA, so it no longer counts toward future required minimum distributions. Roth IRAs have no RMDs during the owner’s lifetime, which lowers the taxable income you must report at 73 or 75. Roth balances also pass to heirs income-tax-free: they still withdraw under the 10-year rule, but without the income-tax bill that inherited traditional accounts carry.

Reducing future RMDs can keep you in a lower bracket in your 70s and 80s; see our guide to required minimum distributions in 2026 for the schedule. With the 2026 federal estate exemption at $15,000,000, most families face income tax, not estate tax, on inherited retirement accounts, where an inherited Roth’s tax-free treatment helps.

Frequently asked questions

How much tax will I pay if I convert to a Roth IRA?

You will pay ordinary income tax on the full converted amount at your 2026 marginal rates of 10% to 37%, plus any state income tax. Because the conversion stacks on your existing income, the effective rate is usually lower than your top bracket. A retired couple converting $90,000 on top of $50,000 of income might pay a blended federal rate near 16%.

How do I avoid paying taxes on a Roth conversion?

You cannot avoid the tax entirely, because a conversion is taxable by design, but you can reduce it. Convert in low-income years before RMDs and Social Security begin, spread conversions across several years to stay in a lower bracket, and pay the tax from a taxable account rather than the IRA. These steps lower the rate and protect the amount that grows tax-free.

Do Roth conversions count as income?

Yes. A Roth conversion counts as ordinary income and increases your AGI and MAGI for the year. That higher MAGI can raise your Medicare premiums two years later, increase how much of your Social Security is taxable, and affect eligibility for income-based thresholds such as the 3.8% Net Investment Income Tax. The conversion itself is not net investment income.

Does a Roth conversion affect Medicare premiums?

It can. Medicare sets premiums using IRMAA, a MAGI-based surcharge with a two-year lookback. A conversion in 2026 that lifts MAGI above $109,000 (single) or $218,000 (married filing jointly) can raise your 2028 Part B and Part D premiums. IRMAA is a cliff, so crossing a threshold by one dollar moves you to the next tier for the year.

At what age does a Roth conversion not make sense?

There is no single cutoff age, but conversions often make less sense once RMDs and Social Security have started, because the added income is taxed on top of benefits and can trigger the Social Security tax torpedo and IRMAA. Very late in life, if heirs are in a lower bracket than you, leaving pre-tax dollars to them may cost less than converting.

How does a Roth conversion affect my Social Security taxes?

A conversion raises your provisional income, the figure that determines how much of your Social Security is taxable. As it climbs, up to 85% of your benefit becomes taxable. When a dollar of conversion also makes 85 cents of benefit taxable, the effective marginal rate on that dollar can reach about 40.7%. Converting before you claim Social Security usually avoids this.