The Bracket-Filling Mechanic Explained
Every year you have taxable income, you occupy a position in the federal tax bracket structure. If your other income - pension, part-time work, Social Security, interest - places you at $45,000 of taxable income for the year, and the 22% bracket for married filers in 2026 tops out at $211,400 of taxable income, you have roughly $166,000 of unused 22% bracket space. Each dollar you convert from a traditional IRA to a Roth IRA fills that space and costs you 22 cents in federal tax. The insight behind annual conversions is that you are choosing WHEN to pay tax on money that will eventually be taxed. Without conversions, the IRS chooses the timing through Required Minimum Distributions starting at age 73. By that point, RMDs stack on top of Social Security, potentially pushing you into the 24% or 32% bracket. The annual conversion strategy lets you pay 12% or 22% today rather than 24% to 32% on forced distributions later. In 2026, the 12% bracket for married filers extends from $24,801 to $100,800 of taxable income. After the standard deduction of $32,200, a married couple with $40,000 in other income has about $28,000 of space remaining in the 12% bracket before conversion, and the full spread to $211,400 in the 22% bracket beyond that. Sizing each year's conversion to fill those brackets systematically is the core execution of this strategy.
Key Stat: A married couple with $800,000 in a traditional IRA converting $60,000 per year for 13 years at an average 18% blended rate would pay roughly $144,000 in total conversion taxes. Without conversions, RMDs starting at 73 on a grown balance could generate $300,000 or more in cumulative taxes at higher rates.
How to Calculate Your Conversion Amount Each Year
The annual calculation has five steps. First, add up all expected ordinary income for the year: pension payments, part-time earnings, taxable interest and dividends, and any Social Security you are collecting. Second, subtract the 2026 standard deduction - $32,200 for married couples filing jointly, or $16,100 for single filers. That gives you your baseline taxable income before conversions. Third, decide which bracket ceiling you want to stay under. Most retirees in the early conversion years target the top of the 22% bracket ($211,400 taxable income for married filers in 2026) or sometimes the 24% bracket ($403,550). Fourth, subtract your baseline taxable income from that ceiling to get your available conversion space. Fifth, check the IRMAA threshold: for married filers, the first IRMAA surcharge on Medicare Part B kicks in at $218,001 MAGI in 2026. If converting up to your bracket ceiling would push your MAGI past an IRMAA threshold, pull back accordingly. For example: a married couple with $50,000 in baseline taxable income targeting the 22% bracket ceiling of $211,400 has $161,400 of conversion room. But if their MAGI (which includes the full conversion amount before deductions) would exceed $218,001, they should cap the conversion at whatever keeps them below that IRMAA cliff. A $1 overage triggers an $81.20 per person per month Part B surcharge, roughly $1,948 per person annually starting two years later.
The IRMAA Interaction You Cannot Ignore
IRMAA uses your MAGI from two years prior. A large Roth conversion in 2026 affects your Medicare premiums in 2028. This two-year lag means you must plan conversions with a forward-looking view rather than reacting to your current Medicare bill. For 2026, the IRMAA brackets for married filing jointly start at $218,001 MAGI with an $81.20 per person per month Part B surcharge. The next tier begins at $274,001 with a $202.90 surcharge per person per month. For a couple, a conversion that accidentally crosses the $274,001 line costs an extra $4,869 in Part B premiums two years later - on top of the Part D surcharges. Modeling your MAGI carefully each year before finalizing the conversion amount is worth the effort.
- Start conversions the first year your income drops after retirement, before Social Security begins
- Use tax software or a spreadsheet to project taxable income and MAGI for the year before converting
- Convert up to but not past the nearest IRMAA threshold unless the bracket savings clearly outweigh the surcharge cost
- Leave the converted funds in a money market within the Roth IRA for 5 years if you need penalty-free access before age 59.5
- File IRS Form 8606 every year you execute a conversion to document the transaction
- Stop or reduce conversions in years when other income is unusually high - a home sale, one-time business income, or large capital gain
What Happens If You Skip Conversions
The cost of inaction is concrete. A traditional IRA worth $800,000 at retirement that grows at 6% per year reaches approximately $1.43 million by age 73. At that point, the first RMD using the IRS Uniform Lifetime Table factor for age 73 (26.5) is about $54,000. That $54,000 lands on top of whatever Social Security income you are receiving. For a married couple collecting $36,000 per year in combined Social Security, the $54,000 RMD pushes combined income to $108,000 - far above the $44,000 threshold where 85% of Social Security benefits become taxable. The RMD itself is taxed at 22%, and the additional $30,600 of newly taxable Social Security income (85% of the $36,000 benefit) is taxed at the same rate, creating an effective marginal rate of roughly 40% on each RMD dollar in that zone. By age 80, the RMD factor drops to 20.2 and the required distribution from the same account approaches $71,000 or more as the balance has continued growing. The annual Roth conversion strategy interrupts this compounding problem at the lowest possible cost.
Other Tools That Enhance the Strategy
The conversion strategy works best when you can keep your non-conversion income low during the conversion years. A Health Savings Account spent on current medical costs instead of drawing from taxable sources preserves bracket room. Municipal bonds in a taxable account generate interest that is excluded from MAGI for IRMAA purposes, keeping conversion room open. Some retirees use policy loans from an Indexed Universal Life Insurance policy to fund living expenses during the conversion window. Because IUL policy loans do not appear on a tax return and are not counted in MAGI for any purpose, drawing $30,000 from an IUL loan instead of from a taxable brokerage account keeps baseline income low and frees up more bracket room for conversions. This is a specific and narrow use case for IUL - it complements the conversion strategy but is not a reason to purchase IUL on its own. The annual Roth conversion strategy is not exciting or complex. It is disciplined execution of a simple idea repeated every year for a decade or more. The payoff - a large Roth balance generating tax-free income with no RMDs - makes the patience worthwhile.
The IUL Solution: During Roth conversion years, every dollar of extra taxable income competes with conversion dollars for the same bracket space. Some retirees who funded an IUL policy during their working years draw tax-free policy loans for living expenses during conversion years instead of taking distributions from taxable accounts. This keeps their baseline income lower, which frees up more room to convert at 12% or 22% rather than triggering a higher bracket. IUL is one option among several for sourcing tax-free retirement income - alongside Roth accounts and municipal bonds - and the combination can meaningfully extend how much you convert each year at the lowest available rates.
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