5 Roth Conversion Mistakes High-Income Taxpayers Commonly Make

Many high-income taxpayers spend years looking for ways to reduce today's tax bill while overlooking one of the largest future tax liabilities on their balance sheet: their traditional IRA and 401(k) accounts.

Tax-deferred retirement savings are powerful wealth-building tools. However, every dollar contributed to a pre-tax retirement account eventually becomes taxable income. For successful savers, decades of compounded growth can create a surprisingly large tax burden later in life through Required Minimum Distributions (RMDs), Medicare surcharges, and reduced tax flexibility in retirement.

The goal of a Roth conversion is not to avoid taxes altogether. Rather, it is to take greater control over when those taxes are paid. With the passage of the One Big Beautiful Bill Act (OBBB) in 2025, many taxpayers expected Roth conversion planning to become less relevant. In reality, the opposite may be true. The urgency has shifted from beating a legislative deadline to addressing a growing pool of deferred tax liability before the IRS begins forcing distributions.

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Understanding the Roth Conversion Strategy

A Roth conversion allows you to move funds from a traditional retirement account into a Roth IRA.

The mechanics are simple:

• The converted amount is added to your taxable income in the year of conversion.
• You pay ordinary income tax on that amount.
• Future growth inside the Roth IRA becomes tax-free.
• Qualified withdrawals are tax-free.
• Roth IRAs are not subject to Required Minimum Distributions during the owner's lifetime.

In essence, you're voluntarily paying taxes today in exchange for eliminating future taxation on those dollars and their future growth.

The key question is: Will your tax rate be lower today or later? Many taxpayers automatically assume retirement means lower taxes. In reality, that is not always the case.

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The Hidden Tax Trap for Successful Savers

One of the biggest misconceptions about retirement planning is that taxes naturally decline after retirement. For many affluent households, the opposite happens.

Consider a taxpayer who accumulates $1 million in a traditional IRA by age 40. Assuming no additional contributions and an average annual return of 8%, that account could grow to approximately:

• $6.8 million by age 65
• Nearly $15 million by age 75

Under current rules, a $15 million IRA could generate an initial Required Minimum Distribution of more than $600,000 per year, before considering Social Security benefits, investment income, rental income, pensions, or other sources of cash flow.

In other words, the IRS may eventually require the taxpayer to recognize hundreds of thousands of dollars of taxable income annually—whether they need the money or not. The issue is not that the account performed too well. The issue is that no one planned for the tax consequences of that success.

This is precisely where multi-year Roth conversions can become valuable. By gradually moving portions of a traditional IRA into a Roth IRA over time, taxpayers may reduce future RMDs, create more tax-free retirement income, and gain greater control over their long-term tax picture.

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Common Roth Conversion Mistakes

Mistake #1: Missing the Best Roth Conversion Windows

Many taxpayers assume Roth conversions should only be considered close to or after retirement. In reality, some of the best opportunities occur during temporary low-income years.

We've seen taxpayers create valuable conversion windows through:

• Cost segregation studies and bonus depreciation
• Business losses or slower-income years
• Career transitions
• The years between retirement and Social Security
• The years before RMDs begin

A lower-income year does not just reduce taxes today—it may create an opportunity to move future retirement growth into a tax-free environment at a significantly lower tax cost.

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Mistake #2: Converting Too Much in One Year

Many taxpayers view Roth conversions as an all-or-nothing decision.

For example, a taxpayer with a $1 million IRA may decide to convert the entire account in a single year. While the future tax-free growth sounds attractive, the immediate tax consequences can be severe.

Large conversions may:

• Push income into higher tax brackets
• Trigger Net Investment Income Tax exposure
• Reduce eligibility for deductions or credits
• Increase Medicare premiums

In many situations, a multi-year conversion strategy produces a significantly better outcome than a single large conversion.

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Mistake #3: Ignoring Medicare IRMAA

One of the most overlooked consequences of Roth conversions is Medicare premium surcharges.

A conversion may save taxes over a lifetime while simultaneously increasing Medicare premiums two years later. We've seen situations where taxpayers focus entirely on federal tax brackets and fail to realize that crossing an IRMAA threshold can add thousands of dollars of additional healthcare costs.

Roth conversions should always be evaluated within the context of the taxpayer's full financial picture—not just the tax return.

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Mistake #4: Paying the Tax From the Retirement Account

Whenever possible, conversion taxes should be paid using assets outside the retirement account. Using IRA funds to pay the tax reduces the amount that ultimately reaches the Roth and sacrifices future tax-free growth on those dollars.

For younger taxpayers with decades of compounding ahead of them, the long-term opportunity cost can be substantial.

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Mistake #5: Looking at Roth Conversions in Isolation

This is perhaps the most common mistake we see. Roth conversions rarely exist in a vacuum.

The most effective strategies are often coordinated with:

• Cost Segregation Studies
• Real Estate Professional Status planning
• Business income planning
• Defined Benefit and Cash Balance Plans
• Charitable giving strategies
• Retirement timing decisions

The largest opportunities often emerge when multiple planning strategies work together. A Roth conversion may not make sense by itself. But combined with a large depreciation deduction, a lower-income year, or a charitable planning strategy, the economics can change dramatically.

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Final Takeaway

A Roth conversion is ultimately a tax-timing decision. The taxpayers who benefit most are often those who recognize low-income windows and proactively plan before future RMDs force the decision for them.

Like many advanced tax strategies, Roth conversions rarely work in isolation. The best results often come from coordinating them with business income, real estate investments, depreciation strategies, charitable planning, and broader retirement goals.

If you've accumulated significant retirement assets or haven't revisited your Roth conversion strategy in recent years, it may be worth taking a fresh look.