Roth Conversion Taxes 2026: The Real Cost
A 2026 Roth conversion is taxed as ordinary income, but newly taxable Social Security and a shrinking senior deduction can push the real rate above 40%.
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This article is for educational purposes only and is not tax, legal, or financial advice. Examples are hypothetical estimates for the 2026 tax year.
A Roth conversion has no tax rate of its own. The taxable amount is ordinary income for 2026, stacked on top of your other income, and you can’t undo it later.
The usual advice stops at “fill your bracket,” which works for a 60-year-old with a salary. For a retiree on Social Security, it can be off by more than half.
Take a single 67-year-old with $40,000 of Social Security and $30,000 of other income who converts $45,000. Bracket math says the bill is $7,255, and the full return says $11,201.80, because the conversion also makes more of her benefits taxable and shrinks her senior deduction.
That conversion also stops exactly at $109,000 of MAGI, the top of the no-surcharge tier in the 2026 Medicare table. One more dollar would cross it, and the crossing costs $1,148.40 a year at that table’s amounts. The sections below show how to find those numbers for your own return.
How a 2026 conversion is taxed
The IRS treats a conversion as a distribution you include in gross income for the year you convert. If it’s properly rolled over, the 10% additional tax on early distributions doesn’t apply.
Any part that returns your nondeductible basis isn’t taxed, and the pro-rata rule decides that split. The examples here assume every dollar is pre-tax.
Converted dollars sit on top of your other ordinary income and fill the brackets from wherever that income stopped.
| 2026 taxable income | Single | Married filing jointly | Head of household |
|---|---|---|---|
| Top of 12% | $50,400 | $100,800 | $67,450 |
| Top of 22% | $105,700 | $211,400 | $105,700 |
| Top of 24% | $201,775 | $403,550 | $201,750 |
| Top of 32% | $256,225 | $512,450 | $256,200 |
In the simple case, a single 60-year-old with $60,000 of W-2 income has $43,900 of taxable income after the $16,100 standard deduction. That leaves $61,800 of room before the 22% bracket ends.
Converting all of it costs $6,500 × 12% plus $55,300 × 22%, or $12,946, a blended 20.95%. With no benefits and no senior deduction at 60, the Social Security and senior costs below don’t apply.
Bracket tops and income lines measure different things
Bracket tops are taxable income. Medicare surcharges and most phase-outs use MAGI, which sits above taxable income by roughly your deduction. See our guide to AGI for how the two relate.
For a filer under 65 with the basic standard deduction, the top of the 22% bracket equals $121,800 of AGI single and $243,600 joint. Both already clear the first 2026 Medicare lines of $109,000 and $218,000. You can stay inside your bracket and still cross one.
The rules that don’t move
- Deadline: conversions are normally included in income for the year you convert, so December 31 is the line for 2026.
- RMD first: you can’t convert an amount you must take as a required minimum distribution, including in the calendar year you reach 73.
- No undo: conversions made after 2017 can’t be recharacterized, so you can’t reverse one if your income comes in higher than expected.
- Roth contribution room: conversions are subtracted when you figure MAGI for Roth contribution limits. They still count for the tests below.
- Paperwork: your custodian reports the conversion on Form 1099-R, even when the money stays with the same trustee.
The One Big Beautiful Bill Act left conversions alone and made the brackets permanent. That removes the old “rates jump in 2026” deadline, though the case for paying tax now can still hold if you expect higher income later.
The second-order costs that raise your real rate
Your real rate is what one more converted dollar adds to your total tax. Four provisions can push it above your bracket, and each one applies only in a certain income range.
Social Security: up to 85 cents per dollar
The test adds half your benefits to all your other income, and a conversion counts as other income. Base amounts are $25,000 single and $32,000 joint, and up to 85% of benefits can be taxable once the total passes $34,000 or $44,000.
Past that second line, each converted dollar can bring 85 cents of benefits into income with it. A 12% bracket becomes 22.2% (12% × 1.85) and a 22% bracket becomes 40.7% (22% × 1.85). Between the two lines, the pull is 50 cents.
This stops at the 85% cap. A retiree already at the cap pays no multiplier, and neither does anyone not yet collecting benefits. To test your own numbers, use the taxable Social Security calculator.
Senior deduction: 6 cents per dollar
The senior deduction is $6,000 per qualifying person for tax years 2025 through 2028. It falls by 6% of MAGI over $75,000 single or $150,000 joint, and it’s gone at $175,000 or $250,000.
Each spouse’s amount shrinks separately, so two seniors lose 12% of the excess combined. Married filing separately doesn’t qualify.
On its own this is a small effect: 22% becomes 23.32% for one senior and 24.64% for two. It matters most when it overlaps the Social Security zone, where 22% becomes 43.14%.
The 0% capital gains rate: 15 points
Long-term gains stack on top of ordinary income. The 0% rate ends at $49,450 of taxable income single, $98,900 joint and $66,200 head of household, so each converted dollar can push a dollar of gain from 0% to 15%.
Say a single filer has $30,000 of ordinary taxable income and a $20,000 long-term gain, which owes $82.50. Convert $10,000 and the gain owes $1,582.50, on top of $1,200 of bracket tax. The conversion costs $2,700, or 27%, on dollars taxed in the 12% bracket.
NIIT and other income tests
A Roth conversion isn’t net investment income, but it does raise the MAGI that exposes investment income to the 3.8% tax. The thresholds are $200,000 single or head of household, $250,000 joint and $125,000 married filing separately.
The tax applies to the smaller of your investment income or your MAGI over the line, so a conversion can add 3.8 points until the excess passes your investment income. The NIIT calculator shows where you stand.
Larger conversions can also reach the MAGI phase-outs for the tips, overtime and car-loan interest deductions.
What the zones look like on one return
Back to our retiree: single, 67, $40,000 of Social Security, $30,000 of other income, standard deduction. Before converting, $18,100 of her benefits are taxable, AGI is $48,100, taxable income is $23,950 and tax is $2,626.
| Conversion dollars | Bracket | Real rate | Why |
|---|---|---|---|
| $0 to $14,297 | 12% | 22.2% | 12% × 1.85 |
| $14,298 to $14,540 | 22% | 40.7% | 22% × 1.85 |
| $14,541 to $18,705 | 22% | 43.14% | 22% × 1.85 × 1.06, MAGI past $75,000 |
| $18,706 to $62,745 | 22% | 23.32% | Benefits at the 85% cap, 22% × 1.06 |
| $62,746 to $111,000 | 24% | 25.44% | 24% × 1.06 |
| $111,001 to $155,925 | 24% | 24% | Senior deduction gone at $175,000 MAGI |
| Above $155,925 | 32% and up | 32% and up | Bracket rate only, nothing multiplied |
The worst stretch is short, and the rate falls after it. Dollars past $18,705 cost about half of the ones just before them, so stopping at $14,000 isn’t automatically the cheap answer.
At $45,000, her other income is $75,000, taxable benefits are $34,000, and AGI and MAGI are $109,000. Her senior deduction drops to $3,960, taxable income lands at $86,890 and tax comes to $13,827.80.
The added $11,201.80 is 24.9% of the conversion, against the 16.1% that bracket math shows.
The zones change with the person. With $30,000 of benefits and $20,000 of other income, the multiplied zone ends at a $23,705 conversion and the rate drops to a plain 12% until $29,050.
Couples usually escape the worst overlap
A couple, both 67, with $60,000 of benefits and $50,000 of other income starts with $39,100 of taxable income and $4,196 of tax.
| Conversion dollars | Real rate |
|---|---|
| $0 to $16,941 | 22.2% |
| $16,942 to $47,300 | 12% |
| $47,301 to $49,000 | 22% |
| $49,001 to $146,232 | 24.64% (22% × 1.12) |
| $146,233 to $149,000 | 26.88% (24% × 1.12) |
| Above $149,000 | 24% and up (bracket rate only) |
Their benefits hit the cap while they’re still in the 12% bracket. For a couple like this on the standard deduction, reaching the 40.7% zone takes combined benefits above about $82,500.
Premium costs tied to MAGI
These two costs sit outside bracket math, and a conversion can trigger both.
Under 65 on a Marketplace plan
A conversion raises the household income that sets your premium tax credit. The statute’s waiver of the 400% limit covers only tax years before 2026, so for 2026 coverage the credit ends above 400% of the poverty line: $62,600 single and $84,600 for a couple (48 states and DC, higher in Alaska and Hawaii).
The repayment cap is gone too. Starting in 2026, excess advance credits are repaid in full at filing. A February 2026 healthinsurance.org report said Congress had not extended the enhanced subsidies, so check for later action before you rely on this.
The credit also shrinks before the cliff. From 300% to 400% of the poverty line, your expected contribution is 9.96% of income, so each added dollar costs 9.96 cents of credit.
Take a single 62-year-old with $50,000 of MAGI and an illustrative $10,000 benchmark plan. Her credit is $5,020.
Converting $12,600 lands exactly on $62,600, cuts the credit to $3,765.04, and adds $1,512 of tax. That’s a 21.96% real rate in the 12% bracket.
One dollar more and the credit is $0, so that last dollar costs $3,765.04. Below 300% the slope is steeper: about 16.4 cents per dollar at $40,000 and 18.3 cents at $45,000.
All of this assumes the benchmark exceeds your expected contribution and your plan costs at least the credit.
On Medicare, two years later
Medicare’s income surcharge, IRMAA, uses your tax return from two years back. A 2026 conversion sets 2028 premiums, so this matters from age 63.
MAGI here is AGI plus tax-exempt interest, and the tiers are cliffs: one dollar over brings the whole add-on.
The table shows the 2026 add-ons. Part B add-ons are charged on top of the $202.90 standard premium, and Part D add-ons on top of your drug plan’s premium. They apply to 2024 income, so treat them as an illustration.
| MAGI, individual return | MAGI, joint return | Part B add-on per month | Part D add-on per month |
|---|---|---|---|
| Up to $109,000 | Up to $218,000 | $0 | $0 |
| Over $109,000 to $137,000 | Over $218,000 to $274,000 | $81.20 | $14.50 |
| Over $137,000 to $171,000 | Over $274,000 to $342,000 | $202.90 | $37.50 |
| Over $171,000 to $205,000 | Over $342,000 to $410,000 | $324.60 | $60.40 |
| Over $205,000, under $500,000 | Over $410,000, under $750,000 | $446.30 | $83.30 |
| $500,000 or more | $750,000 or more | $487.00 | $91.00 |
Your 2026 income will be measured against the 2028 table, which won’t exist by the December 31 deadline. Tiers are indexed each year, so its lines will likely sit higher. Married people filing separately have a different table.
The first tier costs $95.70 a month, or $1,148.40 a year per person and $2,296.80 for a couple both on Medicare. The second costs $2,884.80 a year per person.
Our retiree would land in that first tier if she filled the 22% bracket, which takes $62,745 and puts MAGI at $126,745.
SSA’s list of life-changing events includes work stoppage, divorce and the death of a spouse, among others. A Roth conversion isn’t on the list, so it isn’t grounds to ask for a lower surcharge. If your income falls back the next year, the surcharge is a one-year cost.
After you convert: paying the bill and the five-year clock
Why not to withhold from the conversion
Withheld money never reaches the Roth. Convert $50,000 with 22% withheld under age 59½, and $11,000 goes to the IRS while $39,000 lands in the Roth. All $50,000 is still taxable, and the $11,000 likely carries $1,100 of 10% additional tax, assuming no exception applies.
Over 59½ the $1,100 disappears, but the Roth is still $11,000 short. Paying from outside money is what makes a conversion beat leaving the money in place at equal rates. Selling assets at a gain to raise that cash has its own cost, so count it.
Watch the defaults, too:
- IRA payouts: Form W-4R sets a default 10% withholding rate unless you enter another. If you’ll pay through other withholding or estimated payments, you can enter “-0-”.
- Plan payouts to you: these carry a 20% default rate, and you can’t choose less.
- Direct moves: a direct rollover from a 401(k) or other workplace plan to a Roth IRA generally has no tax withheld. An IRA conversion is still reported as an IRA distribution, even trustee to trustee or at the same custodian, so expect the 10% default unless you enter “-0-” on Form W-4R.
Paying without an underpayment penalty
A conversion can leave you short on pay-as-you-go tax, and Pub 590-A warns you may need more withholding or estimated payments. You generally avoid the penalty if withholding and timely estimates reach the smaller of 90% of this year’s tax or 100% of last year’s. That rises to 110% if last year’s AGI was over $150,000 ($75,000 married filing separately).
For a late-year conversion, you have two practical routes:
- Estimated payment: the fourth-quarter due date is January 15, 2027. Income that arrives late in the year may need the annualized income method in Form 2210’s Schedule AI to avoid a penalty for earlier quarters.
- Extra paycheck withholding: withheld tax counts as paid in equal parts on each due date unless you show otherwise. That timing is withholding’s one real advantage, and a higher Form W-4 amount gets it without shrinking the Roth.
Plan for the next year as well. A 2026 conversion that lifts AGI over $150,000 moves you to the 110% test for 2027, measured on a larger tax bill. The estimated tax calculator helps you size those payments.
The two five-year clocks
The conversion clock is separate for each conversion and starts on the first day of the tax year you convert. Any 2026 conversion starts January 1, 2026, and the period runs through December 31, 2030, so a December conversion gets almost a full year of credit.
Take converted money out sooner and you may owe the 10% additional tax, though the exceptions include reaching 59½.
The qualified-distribution clock starts with the first tax year for which you made any contribution to a Roth IRA. Earnings come out tax-free only after that period and once you meet a condition such as reaching 59½, disability or death.
Withdrawals follow a fixed order: regular contributions first, then conversions oldest first (taxable part before nontaxable), then earnings.
How to size your 2026 conversion
- Get a baseline without the conversion. You need AGI, taxable income and tax. If your income comes from W-2s, 1099-INT, 1099-DIV and Social Security benefits, Tax47 estimates all three for free, and its Tax Summary shows the taxable Social Security and senior deduction rows.
- Know what that estimate leaves out. The app has no 1099-R, pension or IRA input, so it can’t model the conversion itself, and it isn’t a complete baseline if you live on a pension, IRA withdrawals or RMDs. In that case, start from last year’s return. It also estimates federal tax only and files nothing.
- Mark your nearest lines. List your next bracket top, the Social Security lines, the $75,000 or $150,000 senior line, the 0% gains top and any premium line that applies. Compare each one on its own measure: taxable income for brackets, MAGI for the rest.
- Run the bracket math. The Roth conversion calculator takes your taxable income, conversion amount, filing status and state. It’s bracket-only: it adds no Social Security or senior deduction effect, and its own note says it doesn’t account for the pro-rata rule, nondeductible contributions, AMT, IRMAA or ACA premium impacts.
- Add the multipliers yourself. Use the table below for each range the conversion crosses.
- Add state tax. State income tax can raise the bill further. The Roth conversion calculator’s state input gives a starting estimate.
| If the conversion dollar falls in | Real rate is roughly |
|---|---|
| The 85% Social Security zone | Bracket × 1.85 |
| The senior deduction phase-out | Bracket × 1.06, or × 1.12 for two seniors |
| 300% to 400% of the poverty line, on a Marketplace plan | Bracket + 9.96 points |
| Gains pushed out of the 0% rate | Bracket + 15 points |
| NIIT, while investment income exceeds the MAGI excess | Bracket + 3.8 points |
Then compare that real rate with the one you expect on the same money later. A 43% dollar is hard to justify against a future 22% bracket, while a 23% dollar might be a fair trade. Our Roth vs. traditional breakdown covers that side of the decision.
Sources & References
- IRS Publication 590-A: conversion rules, RMD limit, recharacterization, withholding on a plan’s direct rollover to a Roth IRA and the pay-as-you-go warning.
- IRS Publication 590-B: taxability of distributions, the five-year periods and the withdrawal order.
- IRS Publication 915: Social Security base amounts and worksheet (2025 edition; the amounts aren’t indexed).
- IRS Publication 505 and Form 2210 instructions: safe harbors, the 110% test, withholding timing and Schedule AI.
- IRS Form W-4R: default withholding on IRA and plan payouts.
- IRS rollovers page: no withholding on a plan’s direct rollover.
- Form 8606 instructions and Form 1099-R instructions: Roth contribution MAGI, how custodians report conversions and withholding on IRA distributions.
- Rev. Proc. 2025-32: 2026 brackets, standard deductions and capital gains breakpoints.
- 26 USC §151: the senior deduction and its phase-out.
- IRS NIIT questions and answers and Reg. §1.1411-8: NIIT thresholds and the treatment of Roth conversions.
- 26 USC §36B and Rev. Proc. 2025-25: the premium tax credit, the repayment rule and 2026 contribution percentages.
- HealthCare.gov poverty level glossary: the guideline amounts used for 2026 coverage.
- CMS 2026 Medicare Parts A and B: the 2026 standard Part B premium.
- SSA POMS HI 01101.020, HI 01101.010 and HI 01120.001: IRMAA tables and lookback, MAGI, and life-changing events.
Figures reflect the 2026 tax year and the One Big Beautiful Bill Act (P.L. 119-21). This article is for educational purposes only and is not tax, legal, or financial advice. Always verify current figures with the IRS or a qualified tax professional before acting.
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Frequently Asked Questions
How much tax will I pay on a Roth conversion in 2026?
There is no flat rate. The taxable part of the conversion is added to your other income and taxed bracket by bracket. Your real rate can run higher than your bracket if the conversion also makes more Social Security taxable, shrinks the senior deduction, or pushes long-term gains out of the 0% rate.
How much can I convert without moving to a higher bracket?
Subtract your taxable income from the top of your current bracket. The top of the 22% bracket in 2026 is $105,700 of taxable income for single filers and $211,400 for joint filers. Check the income lines that use MAGI too, since Medicare and other tests measure income before your deduction.
Does a Roth conversion make my Social Security taxable?
It can, up to the cap of 85% of benefits, because the conversion counts as other income in the benefit formula. The formula compares half your benefits plus other income to $25,000 and $34,000 for single filers, or $32,000 and $44,000 for joint filers. If 85% of your benefits are already taxable, a conversion adds no more.
Does a 2026 Roth conversion raise my Medicare premiums?
Possibly, in 2028, because Medicare surcharges look back two years. In the 2026 table the first surcharge starts above $109,000 of MAGI on an individual return and $218,000 on a joint return. The 2028 lines that will apply to 2026 income aren't published yet.
Can I lose my ACA subsidy from a Roth conversion?
Yes. For 2026 coverage, household income over 400% of the poverty line ($62,600 single, $84,600 for a couple in the 48 contiguous states and DC) means no premium tax credit, and advance credits are repaid with no cap. Below that line, each added dollar still shrinks the credit.
Should I have taxes withheld from my Roth conversion?
Usually not. Withheld dollars never reach the Roth, and under age 59 and a half they can carry the 10% additional tax. A payout from an IRA defaults to 10% withholding, and Form W-4R lets you enter -0- if you will pay through other withholding or estimated payments.
What is the five-year rule for Roth conversions?
Each conversion has its own five-year period, starting January 1 of the conversion year. Taking converted money out early may trigger the 10% additional tax unless an exception applies, such as reaching age 59 and a half. A separate five-year period decides whether earnings can come out tax-free.
Can I undo a Roth conversion?
No. Conversions made after 2017 can't be recharacterized back to a traditional IRA. To lower the risk of overshooting, convert late in the year, once your income is clearer, or convert in smaller pieces.