Paying a larger tax bill on purpose can feel wrong, especially in retirement when every dollar seems more valuable.
William reached that point after looking beyond this year and seeing how a large pretax IRA could create bigger required withdrawals, less tax flexibility, and higher taxable income later.
Waiting simply to avoid tax now did not automatically mean paying less tax overall. A big Roth conversion offered another path: accept a known tax cost today to move money into an account with different future tax rules.
The key was deciding whether the long-term tradeoff justified the painful bill this year.
A Roth Conversion Does Not Make the Tax Disappear
William’s decision started with a simple fact. A Roth conversion is not a tax loophole.
When money that has never been taxed moves from a traditional IRA into a Roth IRA, the taxable portion of that conversion is generally included in gross income for that year.
The IRS also allows taxpayers to convert traditional IRA money regardless of income, even when their income is too high to make a normal direct Roth IRA contribution.
The appeal comes later. Qualified Roth IRA distributions generally are not included in taxable income, while withdrawals of deductible contributions and earnings from a traditional IRA generally are taxable.
| Money left in traditional IRA | Money converted to Roth IRA |
|---|---|
| Tax is generally deferred | Taxable conversion is generally recognized now |
| Future taxable withdrawals may raise income | Qualified future Roth withdrawals can be tax free |
| Generally subject to owner RMD rules | Original Roth IRA owner has no lifetime RMD |
| Larger pretax balance remains | Pretax balance is reduced |
| More future income depends on tax rules then | More future spending can come from Roth assets |
William therefore was not deciding between paying tax and avoiding tax.
He was deciding when to recognize taxable income and how much control he wanted over taxable income later.
That distinction became the foundation of his case for making a large conversion.
What William Was Really Buying With a Bigger Tax Bill
The benefit William wanted was flexibility.
Suppose retirement spending one year requires money for a new roof, a major trip, help for a family member, or another large expense. Taking that money from a traditional IRA can increase taxable income because taxable traditional IRA distributions generally become part of gross income.
A retiree with both traditional and Roth money has another choice. Depending on the circumstances, some spending may be covered with qualified Roth withdrawals without adding those withdrawals to taxable income.
That flexibility can become useful when several income sources are already arriving automatically.
Social Security may be coming in. A pension may be arriving every month. Required distributions may eventually begin. Interest, dividends, or investment sales may add still more income.
William did not know exactly what his future tax rate would be.
Nobody does.
His reasoning was that keeping nearly all retirement savings in pretax accounts would leave him with fewer choices if taxable income became harder to control.
A Roth conversion moved some money from the “tax later” bucket into the “tax paid earlier” bucket.
That did not guarantee lower lifetime taxes. It simply gave him a different mix of accounts to work with.
Why the 2026 Tax Brackets Matter More Than the Conversion Size
Calling a conversion “big” can be misleading.
A $50,000 conversion may be very large for one household and relatively modest for another. The more useful question is how much additional taxable income fits into the tax range a household is willing to accept.
For tax year 2026, the IRS says the standard deduction is $16,100 for single filers and $32,200 for married couples filing jointly. The federal income tax system continues to use seven marginal rates ranging from 10% through 37%.
Here are several of the 2026 taxable income ranges that matter most when examining a retirement conversion.
| Federal rate | Single taxable income | Married filing jointly taxable income |
|---|---|---|
| 10% | Up to $12,400 | Up to $24,800 |
| 12% | $12,401 to $50,400 | $24,801 to $100,800 |
| 22% | $50,401 to $105,700 | $100,801 to $211,400 |
| 24% | $105,701 to $201,775 | $211,401 to $403,550 |
| 32% | $201,776 to $256,225 | $403,551 to $512,450 |
| 35% | $256,226 to $640,600 | $512,451 to $768,700 |
| 37% | Over $640,600 | Over $768,700 |
These are taxable income ranges, not gross income ranges. Deductions and other parts of the return affect where a taxpayer actually lands.
That matters when planning a conversion.
For illustration, suppose a married couple expects $130,000 of taxable income before a Roth conversion. The top of the 22% bracket is $211,400 in 2026.
The simple difference is $81,400.
That does not automatically mean converting $81,400 is the correct move. Social Security taxation, deductions, investment income, Medicare planning, state taxes, and other factors could change the real cost.
But the calculation provides a starting point.
William’s goal was not to choose a large round number such as $100,000 simply because it sounded meaningful. He wanted to identify a tax range he was comfortable using and then test how a conversion would interact with the rest of his return.
That is a much better question than asking, “How much can I convert?”
There is no general income ceiling stopping a Roth conversion. The practical limit is how much additional tax and related costs make sense for the household.
William Was Also Looking Ahead to RMDs
Another part of William’s reasoning involved required minimum distributions.
Traditional retirement accounts cannot always remain untouched forever. Current federal rules set the applicable RMD age at 73 for people who reach age 73 before 2033. The applicable age becomes 75 for those who reach age 74 after December 31, 2032.
The exact start age therefore depends on birth year.
William’s concern was simpler. If a large pretax account continued growing, future required distributions could also become larger.
A Roth conversion reduces the amount remaining in the pretax IRA. Money properly moved to William’s Roth IRA would no longer be part of his traditional IRA balance used for future traditional IRA RMDs.
Roth IRAs also have an important difference for the original owner. The IRS states that the original Roth IRA owner is not required to take lifetime distributions from that Roth IRA.
That gave William another form of control.
He could leave Roth money invested when he did not need it rather than withdrawing money simply because an RMD formula required a distribution from a traditional account.
There is one important rule for people who are already taking RMDs.
An RMD that must be distributed for that year cannot itself be converted to a Roth IRA. The required amount generally has to come out first. Additional eligible funds can then be considered for conversion.
The Hidden Costs That Can Make a Big Roth Conversion Too Expensive
William knew that looking only at the federal tax bracket could produce a bad decision.
A conversion raises income, and income is used in several other tax and benefit calculations.
That means the real cost can be higher than simply multiplying the conversion by a federal marginal tax rate.
| Issue to check | Why a Roth conversion matters |
|---|---|
| Social Security taxation | More income may make a larger portion of benefits taxable |
| Medicare IRMAA | Higher MAGI can lead to higher Part B and Part D costs later |
| Senior deduction | Higher MAGI can reduce the enhanced deduction for eligible adults 65+ |
| Marketplace insurance | Higher household income can reduce or eliminate premium tax credits |
| Capital gains | Added ordinary income can affect how other income is taxed |
| State income tax | State treatment varies widely |
| Estimated tax | A large conversion may require additional withholding or payments |
Social Security Can Become More Taxable
For retirees receiving Social Security, the conversion needs another calculation.
Federal rules use Social Security benefits plus other income to determine how much of those benefits becomes taxable. Depending on income, as much as 85% of Social Security benefits can be included in taxable income. That does not mean Social Security is taxed at an 85% tax rate.
The base amounts used in the calculation remain $25,000 for a single filer and $32,000 for a married couple filing jointly, with higher thresholds involved in determining whether up to 85% may become taxable.
A conversion therefore can create two layers of additional taxable income.
The conversion itself is taxable, and it may cause more Social Security benefits to become taxable.
That is one reason William did not judge the conversion simply by looking at his nominal tax bracket.
Medicare IRMAA Can Show Up Later
Medicare creates another delayed effect.
For 2026, the standard Medicare Part B premium is $202.90 per month. Higher income beneficiaries can pay an Income Related Monthly Adjustment Amount, or IRMAA, on Part B and Part D. For 2026, IRMAA begins above MAGI of $109,000 for individual filers and $218,000 for married couples filing jointly.
Those figures should not be used as future IRMAA thresholds because Medicare adjusts them over time.
What matters for conversion planning is the lag.
Social Security generally determines 2026 IRMAA using the federal tax return for tax year 2024.
Following that normal two year pattern, a conversion completed during 2026 would generally be expected to affect the IRMAA calculation used for 2028 Medicare premiums. The actual 2028 thresholds and premium amounts are not yet known in 2026.
William therefore had to think beyond April’s tax return.
A conversion that looks affordable from an income tax standpoint can still have another cost several years later.
People 65 and Older Need to Check the Enhanced Senior Deduction
Current law adds another wrinkle for older taxpayers.
For tax years 2025 through 2028, eligible taxpayers age 65 or older may receive an enhanced senior deduction of as much as $6,000 per qualifying person, or $12,000 when both spouses on a joint return qualify.
The deduction begins to phase out when modified adjusted gross income exceeds $75,000 for an individual or $150,000 for married couples filing jointly.
A large conversion may push MAGI farther into that phaseout.
That means part of the conversion’s real cost can come from losing a deduction in addition to paying tax on the conversion itself.
William treated that lost deduction like any other conversion expense. It belonged in the calculation before the transaction, not after the tax return arrived.
Retirees Under 65 Have a Different Health Insurance Risk
People who retire before Medicare eligibility may have an even sharper income issue if they buy insurance through the Health Insurance Marketplace.
For 2026, eligibility for the Premium Tax Credit generally returns to the rule requiring household income to be no more than 400% of the applicable federal poverty level, assuming the other eligibility rules are met. The temporary expansion allowing subsidies above 400% applied through tax year 2025.
Marketplace credits are tied to household income.
Because a taxable Roth conversion raises adjusted gross income, a large conversion can reduce a credit or, in some cases, push household income above the eligibility ceiling.
For an early retiree, losing thousands of dollars in health insurance assistance could matter as much as moving into another tax bracket.
This is one of the strongest reasons to model the whole return before converting.
Paying the Conversion Tax Is Part of the Strategy
William also needed a plan for paying the tax.
Creating $50,000, $100,000, or more of additional taxable income without changing withholding or estimated payments could leave a retiree with a large balance due.
Federal income tax generally operates on a pay as you go basis.
For 2026, the IRS generally requires estimated payments when a taxpayer expects to owe at least $1,000 after withholding and credits and does not meet one of the applicable payment thresholds.
A common safe harbor looks at the smaller of 90% of current year tax or 100% of the previous year’s tax. For certain higher income taxpayers, 110% of the previous year’s tax is used instead of 100%.
William therefore treated tax funding as part of the conversion decision.
Where practical, paying the tax with money outside the IRA can leave more of the converted amount inside the Roth account.
That is not automatically the right choice for everyone. A retiree should not empty an emergency fund or create expensive debt simply to keep more money invested.
The better approach is to know where the tax money will come from before pressing the conversion button.
When a Big Roth Conversion May Be the Wrong Move
A Roth conversion can be useful without being useful for everyone.
William’s case would become much weaker if his current marginal tax cost were unusually high and he had strong reasons to expect much lower taxable income later.
The same problem appears when the conversion creates other expensive consequences.
A retiree who loses a large Marketplace premium tax credit, enters a costly Medicare IRMAA tier, loses part of the enhanced senior deduction, or faces a high state income tax may discover that the effective cost is much higher than expected.
Cash also matters.
If paying the conversion tax would force someone to sell needed assets, drain emergency reserves, or borrow at an unfavorable rate, the long term tax benefit may not justify the immediate strain.
Charitable plans deserve attention too.
Someone who regularly gives to charity after age 70½ may eventually be able to use qualified charitable distributions from an IRA. IRS rules allow eligible QCDs to be excluded from taxable income when the requirements are met, and QCDs can count toward an RMD.
Converting every available traditional IRA dollar could reduce the pool of IRA money available for that strategy later.
The answer is therefore rarely “convert everything” or “convert nothing.”
For many retirees, the more practical approach is a series of planned conversions across several tax years.
William’s Seven Step Roth Conversion Check
A Roth conversion should be treated as a full retirement income decision, not simply a one line tax calculation.
Project Income Before the Conversion
Add expected wages, pensions, IRA withdrawals, interest, dividends, investment gains, business income, taxable Social Security, and other income. Then estimate deductions.
Goal: See where additional conversion income could land on the tax return.Measure Available Tax Bracket Room
Choose the tax range you are willing to use before choosing the conversion amount. Estimate how much taxable income remains before reaching the next bracket.
Compare a smaller, middle, and larger conversion instead of relying on one number.Check the Costs Beyond the Tax Bracket
Review Social Security taxation, Medicare IRMAA, the enhanced senior deduction, Marketplace subsidies, capital gains, deductions, credits, and state taxes.
A conversion can cost more than the federal marginal tax rate suggests.Check for Nondeductible IRA Basis
Previous nondeductible IRA contributions can affect how much of a conversion is taxable. Review Form 8606 records before assuming the entire amount will be taxed the same way.
Tax software or professional help can be useful when IRA basis is involved.Decide How the Tax Will Be Paid
Plan for the tax before converting. Possible sources include additional withholding, estimated tax payments, available taxable cash, or another planned source.
Avoid creating a conversion first and figuring out the tax bill later.Use a Direct Transfer When Practical
A trustee to trustee transfer or an internal transfer at the same financial institution can make the process simpler and reduce the chance of an avoidable rollover mistake.
The account provider handles the transfer, but the tax decision still belongs to the household.Check the Number Again Before Year End
Review actual income before completing the final conversion. Investment gains, part time work, pensions, bonuses, property sales, and other income can change the calculation.
Roth conversions generally cannot simply be reversed later because the tax result was unfavorable.Is the Case for a Big Roth Conversion Strong or Weak?
William found it helpful to stop thinking about Roth conversions as automatically good or bad.
The circumstances matter more than the label.
| A stronger case may exist when | A weaker case may exist when |
|---|---|
| Current taxable income is unusually low | Current taxable income is unusually high |
| Large pretax balances may create sizable future RMDs | Future taxable income is expected to be much lower |
| Tax can be paid without damaging cash reserves | Paying the tax would strain available cash |
| The conversion stays within an acceptable tax range | The conversion spills into an unwanted tax range |
| Medicare or Marketplace effects have been modeled | Health insurance costs would rise sharply |
| The retiree wants greater tax diversification | Most future spending will already come from low tax sources |
| Roth money can remain invested for years | The money will probably need to be withdrawn soon |
None of these factors produces an automatic answer.
They simply show why two retirees with identical IRA balances can reasonably reach different conclusions.
