Is a Roth conversion the same as a Roth contribution?

No. A contribution is new money inside the annual IRA or 401(k) limit. A conversion moves existing pre-tax money to Roth. There is no dollar cap on conversions. The converted amount is ordinary income this calendar year. You cannot convert last year’s money in April the way you can still fund last year’s IRA.

What is the 2026 room in the 12% and 22% brackets?

Rev. Proc. 2025-32: 12% ends at taxable income $50,400 single / $100,800 married filing jointly. 22% ends at $105,700 / $211,400. 24% ends at $201,775 / $403,550. Standard deduction is $16,100 single / $32,200 joint / $24,150 head of household. Filling 12% on purpose in a gap year usually beats minimizing this year’s tax to $0 and exploding at RMD age.

Should I pay the conversion tax from the IRA?

Usually no. Withholding from the converted dollars shrinks the Roth, can create a 10% penalty if you are under 59½ on the withheld slice, and still leaves the full conversion in MAGI. Pay from taxable cash if you can. If you cannot, convert less.

Can I undo a Roth conversion?

No. Recharacterization of conversions was repealed for conversions after 2017 (Tax Cuts and Jobs Act). Contributions can still be recharacterized in some cases; conversions cannot. Run the number before December 31.

Does a conversion count as net investment income?

No. Ordinary IRA or 401(k) conversions are not net investment income. They do raise MAGI, and MAGI is the other half of the NIIT test. If you already have capital gains, dividends, or other NII, a conversion can pull that NII over the $200,000 single / $250,000 joint floor (IRC §1411, not indexed).

What are the two 5-year clocks?

Each conversion has its own 5-year clock: withdrawing that converted principal before both age 59½ and five years can add a 10% penalty. Separately, a Roth account must be open five years before earnings come out tax-free. Qualified withdrawals after 59½ still need that account-level clock. Pub. 590-B.

Is this the same as a backdoor or mega backdoor Roth?

No. A backdoor is a nondeductible IRA contribution plus a conversion, used when MAGI blocks a direct Roth. A mega backdoor is after-tax 401(k) plus an in-plan Roth conversion, limited by the 415(c) cap. This page is a taxable conversion of money that is already pre-tax. If the IRA still holds after-tax basis, Form 8606 pro-rata applies — that math lives on the backdoor calculator.

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Roth conversions: fill 12% or 22%, then stop for IRMAA

Q: When does a conversion hit IRMAA?

Medicare IRMAA uses MAGI from two years earlier. A 2026 conversion is 2028 IRMAA. The published CMS 2026 table (standard Part B $202.90; first surcharge above MAGI $109,000 single / $218,000 joint) is a stand-in, not 2028 law. Those floors will be higher. Crossing a cliff adds Part B and Part D surcharges for the whole premium year, per enrollee.

You pick a dollar amount in a traditional IRA or pre-tax 401(k), move it to Roth, and add that amount to this year’s ordinary income. After that, qualified growth and withdrawals are tax-free. There is no annual cap. The cap is your bracket, your cash to pay the IRS, and the Medicare cliff two years out.

Updated 2026-09-13 · 11 min read · Educational, not tax or Medicare advice. Run the conversion calculator with taxable income and MAGI. Do not rebuild the IRA backdoor or the mega backdoor here.

Three Roth moves, one word people mash together

	Contribution	Conversion	Backdoor / mega
What moves	New earned money	Existing pre-tax balance	After-tax contribution, then convert
2026 cap	IRA $7,500 / $8,600 at 50+ (Notice 2025-67)	None	IRA cap, or leftover 415(c) in the plan
Tax this year	Roth: none. Traditional: deduction if allowed	Ordinary income on the pre-tax slice	Usually $0 if no earnings and no pro-rata
Deadline	IRA: April 15 of next year	December 31 of this year	Contribution clock plus a same-year convert

A conversion in March 2027 is a 2027 conversion even if you are still allowed to fund a 2026 IRA. There is no “prior-year conversion.” Custodians will let you try; the 1099-R will not play along.

Worked slice

Single, taxable $84,000, MAGI $100,000

Already in 22%. Room to the top of 22% is $21,700 ($105,700 − $84,000). Extra federal tax is $4,774 (all at 22%). MAGI after is $121,700, which is the first 2026 IRMAA tier (above $109,000, at or under $137,000). If one person is on Medicare two years later, Part B + Part D extra is $95.70/mo × 12 = $1,148 using the CMS 2026 table as a stand-in. All-in about 27% on that slice. Fill-12 is $0 — you already left 12% behind.

The usual “no”

Pay the tax from the IRA

Convert $21,700 and withhold $4,774 from the same IRA and you deposited $16,926 in Roth, still reported $21,700 of MAGI, and if you are under 59½ the withheld slice can be a 10% penalty. Pay from a taxable account. If the cash is not there, convert the amount whose tax you can write a check for.

2026 ordinary brackets (the conversion table)

Rate	Single taxable	MFJ taxable
10%	$0 – $12,400	$0 – $24,800
12%	$12,400 – $50,400	$24,800 – $100,800
22%	$50,400 – $105,700	$100,800 – $211,400
24%	$105,700 – $201,775	$211,400 – $403,550
32%	$201,775 – $256,225	$403,550 – $512,450
35%	$256,225 – $640,600	$512,450 – $768,700
37%	Over $640,600	Over $768,700

Source: Rev. Proc. 2025-32 / IR-2025-103. Standard deduction 2026: $16,100 single and MFS, $32,200 MFJ, $24,150 HOH. Extra at 65 or blind: $2,050 unmarried / $1,650 per spouse. Head of household 12% ends at $67,450; 22% still ends at $105,700. These are taxable income caps, not MAGI. MAGI is what IRMAA and NIIT read.

IRMAA is a two-year MAGI bill, not this April’s 1040

CMS IRMAA for 2026 (the published table, used as a stand-in): first surcharge above MAGI $109,000 single / $218,000 joint. Standard Part B is $202.90/mo. First extra: Part B $81.20 + Part D $14.50 = $95.70/mo per enrollee. Next floors: $137k / $171k / $205k / $500k single (joint doubles until the top two, which are $750k). Married filing separately is compressed. A conversion this year is the MAGI that SSA will read two years later. 2028 floors are not out; they will be higher. Do not freeze 2026 numbers as if they were a 2028 statute.

One dollar over a floor is a full year of surcharge, not a marginal 1%. That is why the calculator has a “stay under IRMAA” button. The thin IRMAA MAGI room widget is still the leftover-under-a-cliff sketch; this page is the conversion tax plus that cliff.

Gap years are the product. Peak-wage years are usually not.

Conversions shine when this year’s ordinary rate is lower than the rate you expect in RMD years: parental leave, a sabbatical, a severance year, early retirement before Social Security and RMDs, a year with big charitable deductions or a NOL. They are a worse trade when you are already in 32%+ and will be in 22% in retirement. “Roth is always better” is a slogan. The 12% sleeve in a gap year is the actual trade.

RMDs start at 73 or 75 depending on birth year. A conversion does not satisfy an RMD. Take the RMD first, then convert (Pub. 590-B). QCDs from an IRA at 70½+ can meet the RMD without MAGI; a conversion cannot. If the goal is MAGI control at RMD age, size conversions in the years before the RMD, not instead of it.

Clocks, NIIT, ACA, and the thing you cannot undo

Two 5-year clocks. Each conversion has its own: converted principal withdrawn before 59½ and before five years can pick up a 10% penalty. The Roth account itself needs five years before earnings are qualified. Turning 59½ does not zero a conversion clock that is still running.

NIIT. The conversion is not net investment income. MAGI is. Thresholds $200,000 single / $250,000 joint / $125,000 MFS have not moved since 2013 (IRC §1411). If you are realizing a large capital gain in the same year, the conversion can make 3.8% apply to that gain. Type NII in the calculator; it is a flag, not a full Form 8960.

ACA. Marketplace subsidies use MAGI on a cliff that is nastier than IRMAA for some households. A conversion that looks cheap on the 12% sleeve can be expensive if it kills a premium tax credit. Enter that MAGI in the same box; this classroom does not scrape Healthcare.gov.

No undo. Recharacterization of conversions died after 2017. You have until December 31, not until April 15. Partial conversions through the year beat a December surprise that lands on a bonus or a capital-gain dump you forgot.

Free tool

Roth conversion calculator

Fill 12% / 22% / 24%, extra federal + state, IRMAA two years out, NIIT flag, shareable URL.

PayPal

Withdrawal + conversion sequence

12-step: harvest 0% LTCG, fill 12%, IRMAA lookback, RMDs as a constraint. No second conversion playbook.

Questions

Is a conversion the same as a contribution?

No. Contribution = new money, annual cap, April IRA deadline. Conversion = existing pre-tax money, no cap, December 31, ordinary income this year.

What is the 2026 12% / 22% room?

12% ends at taxable $50,400 single / $100,800 joint. 22% ends at $105,700 / $211,400. Rev. Proc. 2025-32. Standard deduction is separate.

When does a conversion hit IRMAA?

Two years later. 2026 conversion → 2028 premiums. CMS 2026 first floor $109k / $218k is a stand-in.

Pay the tax from the IRA?

Usually no. You shrink the Roth, keep the MAGI, and can add a 10% penalty under 59½. Pay from cash or convert less.

Can I undo it?

No. Conversion recharacterization is gone after 2017. December 31 is the door.

Is it net investment income?

No. It raises MAGI, which can pull other NII over the $200k / $250k NIIT floor.

Two 5-year clocks?

Per-conversion clock on principal if under 59½, plus the Roth account’s five years for earnings. Pub. 590-B.

Backdoor or mega instead?

Different tools. Backdoor = MAGI blocked a direct Roth. Mega = after-tax 401(k) leftover. This page is pre-tax money you are volunteering to tax now.

Keep reading

Educational only. Confirm Rev. Proc. 2025-32, Pub. 590-A / 590-B, CMS IRMAA for the premium year, and your 1099-R. Written by Thomas Sanders.