Roth Conversion Tax Strategy: When to Convert in 2026

What Is a Roth Conversion?

A Roth conversion is a three-step process:

1. Move money from a traditional IRA, SEP-IRA, Solo 401(k), or 401(k) into a Roth IRA.
2. Pay income tax on the amount converted in the year you convert.
3. Enjoy tax-free growth on the converted funds for life.

Example: You have a $100,000 traditional IRA. You convert $30,000 to a Roth IRA. You owe income tax on $30,000 (taxed at your marginal rate). If you're in the 24% bracket, you owe $7,200 in taxes. But the $30,000 in your Roth IRA now grows tax-free. In 30 years, if it grows to $150,000, you owe no tax on the $120,000 gain—that's the tax savings from converting.

There is no income limit on conversions. The $100,000 MAGI ceiling that used to block high earners was repealed in 2010, which is the whole reason the backdoor Roth exists.

When Conversions Make Sense

1. Low-income years: If you retire before Social Security starts (say, age 60), you might have very low income for a few years. Converting at low tax rates saves substantial taxes. Example:

• Age 60, single. Retirement income is $40,000 (part-time work). After the 2026 standard deduction of $16,100, taxable income is $23,900 and your federal tax is $2,620.
• You convert $50,000 of a traditional IRA to Roth. Taxable income becomes $73,900 and your tax becomes $10,970. The conversion cost $8,350 — an effective rate of 16.7%, because it filled the rest of the 12% band before spilling into 22%.
• Age 67: Social Security starts and income reaches $100,000 without any conversion. Do the same $50,000 conversion then and it costs $12,150 (24.3%), because it lands squarely in the 24% bracket and claws back part of the senior deduction (below).
• Converting at 60 rather than 67 saved about $3,800 on the same $50,000. You can test your own bracket room against your actual numbers in the Roth conversion calculator.

2. Expecting a higher rate when you withdraw: This can happen for several reasons — your own earnings rise, RMDs and Social Security stack on top of each other after 73, a surviving spouse ends up filing single on the same income, or a future Congress raises rates. Converting now locks in today's rate against any of them.

Be clear about which one you are betting on, because only the last is out of your hands — and no rate increase is currently scheduled. The TCJA brackets were due to expire on 31 December 2025, but OBBBA (P.L. 119-21, signed 4 July 2025) made them permanent, so the reversion that older conversion advice was built around did not happen. "Rates could rise someday" is a legitimate reason to hold some Roth as diversification. It is not a deadline, and it should not drive the size or the timing of a conversion.

3. Required Minimum Distribution (RMD) planning: You must start withdrawing from traditional IRAs at age 73 if you were born between 1951 and 1959, and at 75 if you were born in 1960 or later. RMDs increase your income, pushing you into higher tax brackets. Converting early reduces the size of future RMDs and the taxes they trigger — you can see how much a conversion shrinks them by re-running the RMD calculator with a smaller traditional balance.

4. Backdoor Roth strategy: If your income exceeds Roth IRA contribution limits — $153,000–$168,000 MAGI single, $242,000–$252,000 married filing jointly for 2026 — you contribute to a traditional IRA (non-deductible) then immediately convert to Roth. This is legal and widely used by high earners, and it is reported on Form 8606.

5. Spousal conversions: For married couples, if one spouse has a large traditional IRA and the other has minimal income, converting the large IRA when the lower-earner is between jobs avoids the "marriage penalty" and spreads income across two people.

2026 Roth Conversion Math

The cost of converting depends on your marginal tax bracket:

A $50,000 conversion in the 12% bracket costs $6,000 in tax. The same conversion in the 32% bracket costs $16,000. Timing is critical.

That table is the simple version, and it flatters conversions. A conversion large enough to matter almost never stays inside one bracket — it fills the rest of the band you're in and spills into the next one, so your real cost is a blend. The 2026 single brackets end at $12,400 (10%), $50,400 (12%), $105,700 (22%) and $201,775 (24%) of taxable income, which is your income after the $16,100 standard deduction. The gap between the top of your current band and your income is your conversion headroom for the year.

Example: Optimal conversion timing

Year 1 (age 62, single): You retire. Income is $35,000 from part-time consulting. After the $16,100 standard deduction, taxable income is $18,900 and your federal tax is $2,020.

• You convert $35,000 of traditional IRA to Roth. Taxable income becomes $53,900; tax becomes $6,570.
• Tax on the conversion: $4,550 — an effective rate of 13.0%. Most of it was taxed at 12%; only the last $3,500 reached 22%.
• Wait five years instead. At 67 you have $35,000 of Social Security plus the $35,000 of consulting income, 85% of the benefit is taxable, and you now get the extra 65+ standard deduction ($2,050) plus the $6,000 OBBBA senior deduction. Your tax before converting is $4,624. Add the same $35,000 conversion and it becomes $11,671.
• Tax on the conversion at 67: $7,047 — an effective rate of 20.1%. Converting at 62 saved about $2,500 on the identical move.

The senior-deduction trap nobody prices in. The $6,000-per-person deduction OBBBA created for filers 65 and over (2025 through 2028) phases out at 6 cents per dollar of MAGI above $75,000 single / $150,000 joint. Inside that range every conversion dollar is taxed at your bracket plus 6% of your bracket — 22% becomes an effective 23.3%, 24% becomes 25.4%. If you are 65 or older and your MAGI sits below $75,000, the room under that line is the cheapest conversion space you will ever have.

Pro-Rata Rule and the IRA Aggregation Problem

Here's a critical pitfall: the "pro-rata rule." You cannot choose to convert only your after-tax dollars. Every conversion carries the same mix of pre-tax and after-tax money as your IRAs as a whole, and you report the split on Form 8606.

Two details decide the outcome, and both are widely misunderstood:

• The pool is traditional, SEP and SIMPLE IRAs only. Roth IRA balances are not in the calculation. Neither is your 401(k), your 403(b) or your spouse's IRAs — the rule is applied per person, across that person's non-Roth IRAs.
• The balance date is December 31 of the conversion year, plus the amount you converted — not the balance on the day you converted. Rolling a pre-tax IRA into a 401(k) in November still cleans up a conversion you did in March.

Example of the pro-rata trap:

You have a $100,000 traditional IRA, all of it pre-tax, and a $50,000 Roth IRA from prior conversions. You convert $30,000. Your after-tax basis is $0, so the fraction is 0% — the entire $30,000 is taxable. The Roth balance changes nothing.

Now change one fact. Suppose the traditional IRA holds $70,000 of pre-tax money plus $30,000 of non-deductible contributions you already paid tax on:

• Total non-Roth IRA value: $100,000
• After-tax basis: $30,000 → 30% of every dollar you convert comes out tax-free
• Convert $30,000: $9,000 is tax-free, $21,000 is taxable

This rule makes conversions expensive if you have large pre-tax IRAs and cheap if your basis is high. It's why the backdoor Roth works — you contribute after-tax money to a traditional IRA and convert it immediately, and if that non-deductible contribution is your only IRA money, the basis fraction is 100% and the conversion costs nothing. It's also why a single forgotten rollover IRA can quietly make a "free" backdoor Roth taxable.

Run your own basis fraction and tax bill through the Roth conversion calculator before you move any money.

Roth Conversion vs. Backdoor Roth

Both involve getting money into a Roth IRA, but they're different:

• Roth conversion: Moving an existing traditional IRA to Roth. Taxable in full (unless you have after-tax contributions).
• Backdoor Roth: Contributing after-tax money to a traditional IRA, then immediately converting. Taxable only if the traditional IRA had pre-tax money.

The backdoor Roth is better for high earners (who can't contribute directly to a Roth) because the contribution is after-tax (no deduction), so the conversion is tax-free (except for the pro-rata rule on pre-tax IRAs).

State Tax Considerations

Roth conversion taxes are federal. But if you live in a high-income-tax state (California at 13.3%, New York at 10.9%, etc.), the state income tax on a conversion is substantial and should factor into your decision.

Example: You live in California and plan a $50,000 conversion. Federal tax at 22% = $11,000. California tax at 9.3% = $4,650. Total = $15,650. If you move to a no-income-tax state (Texas, Florida) before converting, you save the state tax.

Some retirees specifically relocate to convert after the move, saving state taxes.

Five-Year Rule and Access to Converted Funds

There are two five-year clocks, they do different jobs, and confusing them is the most common Roth mistake there is.

Clock 1 — the conversion clock, one per conversion. Each conversion starts its own five-year period on January 1 of the year you converted. Pull that converted principal back out before the five years are up and you owe a 10% recapture penalty on it, even though you already paid income tax on it. A conversion done any time in 2026 is clear on 1 January 2031.

This clock only bites if you are under 59½. Once you reach 59½, the 10% penalty stops applying to converted principal regardless of how recently you converted. That single fact makes conversions far more flexible for retirees than most articles admit — and far riskier for a 45-year-old planning to spend the money at 50.

Clock 2 — the account clock, one per person, ever. Earnings come out tax-free only if you are 59½ and it has been five years since 1 January of the year you made your first ever Roth IRA contribution or conversion. That clock never restarts, so opening a Roth with even $100 years before you need it is a genuinely free option.

Standard exceptions — death, disability, a first home up to $10,000 — apply to both clocks.

Ordering rules work in your favour. Withdrawals come out contributions first, then conversions oldest-to-newest, then earnings last. You have to exhaust everything else before you touch the earnings that are actually at risk.

Strategic Sequencing: Which Accounts to Tap First in Retirement

Conversions should be part of a larger "withdrawal strategy" that accounts for Social Security, Medicare premiums (which are income-based), and required minimum distributions (RMDs).

Optimal withdrawal sequence in retirement:

1. Taxable brokerage accounts (subject to capital gains tax only).
2. Roth IRA (tax-free, no RMD).
3. Traditional IRA or 401(k) (taxable, triggers RMD).

But before triggering RMDs, consider Roth conversions to get money out of traditional accounts at lower tax rates. This reduces future RMDs and the income-based taxation of Social Security and Medicare premiums.

Risks and Downsides

1. You must pay tax: Conversions create a tax bill in the conversion year. If you don't have outside money to pay the tax, you reduce the conversion benefit (you're paying tax from the conversion itself).

2. IRMAA (Medicare premiums): If your income (including conversions) exceeds $109,000 (single) or $218,000 (joint) for 2026, your Medicare Part B and D premiums jump to the next tier — and IRMAA is a cliff, so one dollar over the line triggers the whole surcharge. Income is measured two years prior, so a 2026 conversion shows up in your 2028 premiums. It applies for one year, not several: IRMAA is recalculated annually from a single year's return, so a one-off conversion produces a one-off surcharge.

3. It cannot be undone: Before 2018 you could recharacterise a conversion — move it back to the traditional IRA and pretend it never happened. TCJA §13611 repealed that for conversions made after 31 December 2017. Once the money moves, the tax bill is fixed, whatever happens to your income later in the year. Convert late in the year, when you know your actual income, rather than early on a projection.

4. Claw-back of credits: High conversions can reduce your claim of education credits, child tax credits, or other income-based credits. If you are on a marketplace health plan, a conversion also raises the MAGI that sets your premium tax credit.

5. Pro-rata rule: If you have traditional IRAs, conversions are partly taxable, reducing the benefit.

FAQ

Can I undo a Roth conversion if my income turns out higher than I expected?

No. TCJA §13611 repealed recharacterisation of conversions for anything done after 31 December 2017. You can still recharacterise a regular Roth contribution into a traditional IRA (and vice versa) up to the extended filing deadline, usually 15 October of the following year — but a conversion is permanent the moment it settles. This is the single strongest argument for converting in November or December, when your year's income is a fact rather than a forecast.

Should I pay the conversion tax out of the IRA itself?

Almost never. If you convert $50,000 and have 22% withheld from the IRA, only $39,000 actually lands in the Roth — you shrank the tax-free account by $11,000 to pay a bill you could have paid from a checking account. Worse, if you are under 59½ the withheld $11,000 is treated as a distribution you did not convert, so it carries a $1,100 early-withdrawal penalty on top. Pay conversion tax from taxable savings, and if that means converting less this year, convert less.

Does a Roth conversion count toward my required minimum distribution?

No, and getting this backwards is expensive. Once you are RMD age, the RMD is the first money out of the account each year and it is not an eligible rollover distribution — it cannot be converted. Take the full RMD, then convert whatever else you want. Converting an amount that included the RMD creates an excess Roth contribution you have to unwind, plus a 6% annual excise tax until you do.

Will a conversion make more of my Social Security taxable?

Yes, and this is where conversions surprise retirees. Once provisional income passes $34,000 single or $44,000 joint, up to 85% of your benefit becomes taxable — and those thresholds were set in 1983 and 1993 and have never been indexed to inflation. In the band where each extra conversion dollar drags 85 cents of benefit into taxable income, a 22% bracket behaves like 40.7%. That is the "tax torpedo," and it is the main reason the gap between retiring and claiming Social Security is such valuable conversion space.

Is there a limit on how much I can convert in one year?

No. There is no dollar cap and no income cap on conversions — only the tax bill. The practical limits are the bracket you are willing to fill, the IRMAA threshold two years out, the 6% senior-deduction phase-out if you are 65 or older, and whether a conversion pushes you past the $200,000/$250,000 MAGI line where the 3.8% net investment income tax starts applying to your dividends and capital gains. The conversion itself is never net investment income, but it raises the MAGI that decides whether your other investment income gets taxed.

Sources

• IRS Publication 590-A, Contributions to Individual Retirement Arrangements (IRAs).
• IRS Publication 590-B, Distributions from Individual Retirement Arrangements (IRAs) — ordering rules and the five-year periods.
• IRS Form 8606 and Instructions, Nondeductible IRAs — the pro-rata calculation.
• Internal Revenue Code §408A(d) (qualified distributions) and §408(d)(2) (IRA aggregation).
• Public Law 115-97 (TCJA) §13611, repealing recharacterisation of conversions.
• Public Law 119-21 (OBBBA, 4 July 2025) §70103, the 65+ deduction and its 6% phase-out.
• IRS Notice 2025-67 and Rev. Proc. 2025-32 — 2026 contribution limits, brackets and standard deduction.
• Social Security Administration, Income Taxes and Your Social Security Benefits — provisional income thresholds.