Roth Conversions 2026: When the Tax Hit Pays Off

A Roth conversion moves money from a pre-tax retirement account — traditional IRA, SEP IRA, SIMPLE IRA, or 401(k) — into a Roth IRA. The converted amount is added to your ordinary income for the year, taxed at your marginal rate, and then grows tax-free forever.

There's no income limit on conversions. Unlike Roth IRA contributions, which phase out for single filers above $165,000 and married filers above $246,000 in 2026, anyone can convert regardless of income. This is the so-called "backdoor" that high earners have used for years.

The deadline is December 31 — not the April tax filing deadline. A conversion counted for 2026 must be completed by December 31, 2026. And conversions are irrevocable — you cannot undo one once it's done.

The core tradeoff: you prepay taxes at today's known rate to avoid paying at an unknown future rate. That bet pays off when your future rate would be higher — from RMDs pushing you into higher brackets, tax law changes, or estate tax exposure.

The 2026 federal tax brackets create specific conversion windows. For married couples filing jointly:

The standard deduction for married filers is $32,200. A couple with no other income can convert roughly $68,600 and stay entirely in the 12% bracket ($100,800 minus $32,200). That's a 12-cent cost for every dollar that will never be taxed again.

The sweet spot for most pre-retirees is the 22% and 24% brackets. A married couple with $80,000 in Social Security and pension income has about $323,550 of room in the 24% bracket ($403,550 minus $80,000 in taxable income). Converting enough to fill that bracket — but not spill into 32% — is the classic bracket-filling strategy.

For single filers, the math is tighter. The 24% bracket caps at $201,775, and the standard deduction is $16,100. A single retiree with $50,000 in income has roughly $135,675 of 24% bracket space.

One thing that changed: the OBBBA made these rates permanent. Before July 2025, the TCJA rates were scheduled to sunset after 2025, meaning brackets would have reset to higher pre-2018 levels. That created genuine urgency to convert. Now there's no sunset — which means the conversion case rests purely on bracket management and RMD avoidance, not on racing a legislative clock.

1. Bracket-filling in low-income years. The highest-value conversion years are when your income is temporarily low — between retirement and age 73 when required minimum distributions kick in, during a sabbatical, or in a year with large deductions. Fill the gap between your current taxable income and the top of your target bracket.

2. Multi-year conversion ladder. Don't convert a $500,000 IRA in one year — that pushes you into the 35% or 37% bracket. Spread it over five to seven years, converting $60,000-$100,000 annually to stay within the 22% or 24% bracket. A $500,000 IRA converted over five years at 24% costs $120,000 in taxes. Converting all at once at a blended 32% costs $160,000. The $40,000 difference compounds for decades inside the Roth.

3. Market-dip conversions. When your IRA drops 20% in a market correction, the conversion tax bill drops proportionally — but the recovery happens tax-free in the Roth. With the S&P 500 at $656.86 (SPY), down 6% from its 52-week high of $697.84 amid tariff uncertainty and $111 oil, this is a better conversion window than it was three months ago. A $100,000 IRA position that dropped to $85,000 saves $3,600 in conversion taxes at 24% — and the recovery to $100,000 happens entirely tax-free.

4. Early retirement bridge. If you retire at 55 and don't collect Social Security until 67, you have 12 years of potentially low income. Converting aggressively during this window — especially in the first few years when you have the most control over taxable income — can dramatically reduce your lifetime tax burden.

5. Pre-RMD conversion sprint. Once RMDs start at age 73, they fill your lower brackets first. A retiree with $1 million in a traditional IRA faces roughly $40,000 in annual RMDs at 73, growing each year as the divisor shrinks. Any conversion on top of RMDs gets pushed into higher brackets. The window between retirement and 73 is the conversion sweet spot — use it or lose it.

The headline tax bracket doesn't tell the whole story. Several "stealth taxes" make conversions more expensive than they look.

Medicare IRMAA cliffs. Conversion income increases your modified adjusted gross income (MAGI), which determines Medicare Part B and Part D premiums two years later. The IRMAA thresholds are cliffs, not gradual: crossing $218,000 MAGI (married filing jointly) or $109,000 (single) by even $1 triggers the full surcharge for the entire year. For a married couple, the first cliff adds roughly $2,100/year in combined Part B and Part D surcharges. Higher tiers at $274,000, $326,000, $410,000, and $750,000 (MFJ) escalate further — the top tier adds over $10,000/year. Use our tax calculator to model the combined federal plus IRMAA cost of different conversion amounts.

The pro-rata rule. If you have both pre-tax and after-tax (non-deductible) money in your traditional IRAs, you can't cherry-pick which dollars to convert. The IRS treats all your traditional IRAs as one pool per Publication 590. If 10% of your total IRA balance is after-tax contributions, then 10% of any conversion is tax-free and 90% is taxable. The workaround: roll pre-tax IRA money into a 401(k) first, leaving only after-tax money in the IRA.

The OBBBA senior deduction trap (2025-2028). The One Big Beautiful Bill Act created a temporary additional deduction for taxpayers 65+: up to $4,000 per person ($8,000 for married couples where both qualify). But it phases out starting at $75,000 MAGI (single) or $150,000 (MFJ). A Roth conversion that pushes MAGI above $150,000 begins clawing back this deduction — adding 1-2 percentage points to the effective marginal rate in the $150,000-$350,000 range. Most conversion calculators don't model this interaction yet.

State taxes. Conversion income is taxable in most states. In California (13.3% top rate) or New York (10.9%), a 24% federal conversion becomes a 37%+ combined rate. Some retirees time conversions to years when they reside in no-income-tax states like Florida or Texas.

Net Investment Income Tax. Conversion income itself isn't subject to the 3.8% NIIT, but it raises your AGI, which can push investment income over the $250,000 threshold for married filers, triggering the surtax on capital gains and dividends you'd otherwise keep.

Not every situation favors conversion. Skip it if:

You're already in a high bracket and expect lower retirement income. A 35% earner who'll retire into the 22% bracket is paying 13 percentage points more than necessary. Wait.

You need the IRA money to pay the tax. Paying conversion taxes from the IRA itself defeats the purpose — you lose the tax-free growth on those dollars and may owe a 10% early withdrawal penalty if you're under 59½.

You're within two years of Medicare enrollment. The IRMAA lookback means a large conversion at age 63 spikes your Medicare premiums at 65. Plan conversions before age 63 or after premiums have already been set.

Your estate plan favors charity. If you plan to leave your IRA to a charity through a qualified charitable distribution, the charity pays no tax on the withdrawal. Converting to a Roth first means you paid taxes the charity never would have owed.

The 5-year rule creates a timing problem. Each conversion has its own 5-year clock before earnings can be withdrawn tax-free (the converted principal is always accessible without penalty after 59½). If you're 50 and need the money before 59½, converted amounts withdrawn within 5 years face a 10% penalty on the taxable portion.

Sarah and Tom, both 62, married filing jointly. Tom just retired; Sarah earns $70,000. Their traditional IRAs total $800,000 — down from $850,000 three months ago due to market volatility. They want to convert as much as possible before RMDs start at 73.

2026 income before conversion:

• Sarah's salary: $70,000
• Interest and dividends: $12,000
• Total: $82,000
• Minus standard deduction: -$32,200
• Taxable income: $49,800

They're in the 12% bracket. Here's their bracket-filling math:

• $51,000 to fill the 12% bracket → tax: $6,120
• $110,600 more to fill the 22% bracket → tax: $24,332
• $192,150 more to fill the 24% bracket → tax: $46,116

Aggressive: $353,750 conversion at ~21.6% blended rate ($76,568 federal tax). But this triggers IRMAA surcharges in 2028 (MAGI of $435,750 crosses the $410,000 tier) and claws back the senior deduction entirely.

Measured: $161,600 over 4 years at 22% blended. Convert $161,600 annually to fill through the 22% bracket — total MAGI stays at $243,600, just above the first IRMAA cliff at $218,000. Cost: ~$30,450/year in federal tax plus ~$2,100/year in IRMAA surcharges. Over four years they convert $646,400 at an all-in effective rate of about 20.5%.

The 4-year ladder costs more upfront than the aggressive approach but avoids the highest IRMAA tiers and keeps the senior deduction partially intact. The "no conversion" scenario assumes $40,000+ annual RMDs starting at 73, taxed at 22-24% for 20+ years. Use the retirement calculator to model your own numbers.