Roth Conversions: Backdoor, Mega Backdoor, and What Comes Next
By Chris Burns · Series 7, 63, 65 · Quema Capital
A Roth IRA is one of the cleanest tax structures in the U.S. tax code. You contribute after-tax dollars, the money grows tax-free, and qualified distributions in retirement come out with no tax at all. The problem: the IRS caps who can contribute directly.
For 2026, Roth IRA contributions phase out starting around $150,000 for single filers and $236,000 for married filing jointly. If you're a high earner, the front door is likely closed.
But there are other doors. This guide covers the three main paths to Roth conversion for people who are over the income limit — including two you've probably heard of and one that most advisors don't discuss.
What Is a Roth Conversion?
A Roth conversion is the process of moving money from a pre-tax retirement account — typically a traditional IRA or a 401(k) — into a Roth IRA. The amount converted is treated as ordinary income in the year of conversion, so you pay taxes on it now. In exchange, the money grows tax-free inside the Roth and comes out tax-free in retirement.
There is no income limit on Roth conversions. Anyone with a traditional IRA can convert, regardless of how much they earn. The income limits that people frequently cite apply only to direct Roth IRA contributions — not conversions.
The basic math: if you expect your future tax rate to be higher than your current rate, converting now and paying taxes at the lower current rate is advantageous. If you expect your future rate to be lower, deferring may make more sense. For most high earners who are already in or near their peak earning years, this calculation is worth running.
Who Roth Conversions Make the Most Sense For
Roth conversions are not automatically the right move. Whether they make sense depends on a few key factors:
Your current tax rate vs. your expected future rate
The fundamental case for converting is paying taxes now at a rate lower than you'd pay later. For people who are currently in a high bracket and expect to stay there in retirement — or who have significant traditional IRA balances that will generate large required minimum distributions — the calculus can still favor conversion. But this should be modeled with a CPA, not assumed.
The ability to pay the tax bill from outside the account
When you convert, the converted amount is taxable income. Ideally, you pay that tax bill from money outside the IRA — not by withholding from the conversion itself. If you have to shrink the conversion to cover the taxes, some of the benefit is lost.
Time horizon
Roth conversions are most powerful when the converted money has years — preferably decades — to grow tax-free inside the account. Converting a large amount at 70 and distributing it at 75 may not generate enough tax-free growth to justify the upfront tax cost.
The SECURE Act inheritance angle
The SECURE Act's 10-year rule changed the calculus for many families with significant traditional IRA balances. Beneficiaries who inherit a traditional IRA generally must empty it within 10 years — and if those 10 years fall during their peak earning years, they'll pay taxes on every distribution at their highest marginal rate. Converting to Roth during the original owner's lifetime can dramatically reduce that burden for heirs.
How the SECURE Act changed inherited IRA rules — and why it matters for planning
The Backdoor Roth Contribution
The backdoor Roth is the most well-known workaround for high earners who are above the direct Roth IRA contribution limits. The mechanics are straightforward:
- Make a non-deductible contribution to a traditional IRA (up to the annual contribution limit — around $7,500 in 2026, with additional catch-up provisions for those 50+)
- Convert that traditional IRA to a Roth IRA shortly after
- Because the contribution was non-deductible — meaning you already paid taxes on that money — the conversion is not taxable (or nearly not, depending on any earnings in the brief interim period)
There is no income limit on non-deductible traditional IRA contributions, and there is no income limit on Roth conversions. The backdoor Roth connects the two.
The pro-rata rule
The complication: if you have other pre-tax traditional IRA balances (from deductible contributions or a rollover from an old 401(k)), the IRS does not let you cherry-pick which dollars you convert. Instead, the conversion is calculated pro-rata across all your traditional IRA balances. If you have $93,000 in pre-tax IRA money and $7,000 in after-tax (non-deductible) money, roughly 93% of any conversion is taxable — not zero. For people with large pre-tax IRA balances, the backdoor Roth is less useful unless those balances are first moved into an employer plan.
The Mega Backdoor Roth
The mega backdoor Roth is a significantly more powerful strategy — but it requires a 401(k) plan that supports it, and not all do.
Here is how it works. Most people know that the standard 401(k) employee contribution limit is $23,500 in 2026. What fewer people know is that the total annual contribution limit — including employee contributions, employer match, and after-tax contributions — is $72,000 in 2026 (or $79,500 with the catch-up contribution for those 50+). The difference between the employee contribution limit and the total limit is the space for after-tax contributions.
If your employer's 401(k) plan allows after-tax contributions and either (a) in-plan Roth conversions or (b) in-service withdrawals to a Roth IRA, you can contribute that gap — potentially $30,000 to $40,000 or more per year — in after-tax dollars, then immediately convert it to Roth. Because those contributions were after-tax, the conversion is not taxable (again, modulo any small gains in the interim).
The catch
Your 401(k) plan documents must explicitly allow after-tax contributions and either in-plan Roth conversions or in-service withdrawals. Many large employer plans support this; many small company plans do not. Check your plan's Summary Plan Description or ask your plan administrator directly. Self-employed individuals with a Solo 401(k) have more flexibility in drafting a plan that allows this.
The mega backdoor Roth has been a target of proposed legislation over the years. It is currently permissible under existing law, but the rules around it are worth monitoring.
Beyond Backdoor and Mega Backdoor
Backdoor and mega backdoor Roth contributions are the two most commonly discussed paths for high earners. Both are real and worth using if you qualify.
But the annual contribution limits cap how much you can put to work each year — $7,000 here, maybe $40,000 there. For investors with large existing traditional IRA balances, these strategies barely move the needle. The real opportunity — and where meaningful tax savings could be found — is in converting a larger portion of a pre-tax IRA while potentially minimizing the effective tax rate on the conversion itself.
A Third Approach
Backdoor and mega backdoor aren't the only options.
There's a private market strategy that can allow high earners to convert a larger amount at a potentially meaningfully lower effective tax cost.
The Two-Family Comparison: 20 Years of Divergence
The best way to understand the value of a Roth conversion is to watch two families make different decisions and see where they end up.
The Garcias
David and Maria Garcia have $800,000 in a traditional IRA at age 60. They have a comfortable retirement income and don't need the IRA money to live. Their tax advisor tells them that Roth conversion is an option — converting $80,000 to $100,000 per year — but they decide to leave the account alone and let it grow. At 80, they pass away. The IRA has grown to approximately $2.2M at a 5% annualized return.
Their son Marcus is 52 when he inherits. He's a physician earning $420,000 per year, comfortably in the 35% federal bracket. The SECURE Act requires him to empty the inherited IRA within 10 years. He takes roughly $220,000 per year. At 35% federal tax, he pays about $77,000 in taxes on each distribution — $770,000 over 10 years. He keeps roughly $1.43M of the $2.2M he inherited.
The Kellys
Jim and Carol Kelly have the same $800,000 in a traditional IRA at age 60. Their advisor recommends a systematic Roth conversion strategy. Over 10 years — years when they're in partial retirement and their income is lower than their working years — they convert $80,000 per year, paying federal tax at a blended rate of roughly 22–24%. Total tax cost over the conversion period: approximately $192,000, paid from their taxable savings.
At 80, they also pass away. Their daughter Camille inherits approximately $1.9M in a Roth IRA. (The account is slightly smaller than the Garcias' because the Kellys paid taxes along the way rather than letting that tax-deferred amount compound.) The SECURE Act still applies — Camille has 10 years to distribute the inherited Roth IRA. But every dollar she takes out is tax-free.
Camille keeps $1.9M. Marcus keeps $1.43M. The Kellys' $192,000 investment in proactive tax planning created roughly $470,000 more for their daughter.
These scenarios are hypothetical illustrations only. They assume a 5% annualized growth rate, no state income taxes, and stable federal tax brackets. Actual outcomes depend on investment performance, tax rates, the beneficiary's income and bracket, and many other factors. These are not projections of any specific investment or tax result.
Practical Considerations Before Converting
A Roth conversion is a real tax event. Before converting, a few things are worth working through with your CPA:
- How much to convert in a given year. The optimal amount is usually dictated by the top of your current tax bracket — converting enough to fill the bracket, but not enough to push into the next one.
- Whether you have the liquidity to pay the tax outside the IRA. If you have to withhold taxes from the converted amount, you're reducing the principal that will grow tax-free.
- The interaction with Medicare premiums. If you're 63 or older, a large Roth conversion can increase your modified AGI and trigger higher Medicare Part B and D premiums (IRMAA surcharges) two years later.
- State income taxes. Roth conversions are generally taxable at the state level as well. If you live in a high-tax state now and plan to retire to a no-income-tax state, deferring conversion may make sense.
- The impact on other income-dependent thresholds. Roth conversions increase your AGI, which can affect the taxation of Social Security benefits, eligibility for deductions, and other income-based calculations.
Roth conversion strategy is one of those areas where working with a CPA who understands private market investing — and the intersection of retirement accounts, tax planning, and estate planning — pays for itself. The mechanics are not complicated. The coordination is.
Frequently Asked Questions
This guide is for informational purposes only and does not constitute tax, legal, or investment advice. Contribution limits, income thresholds, and IRS rules are subject to change. The hypothetical scenarios presented are illustrative only and do not represent projections of any specific investment or tax outcome. The strategies described — including backdoor Roth contributions, mega backdoor Roth contributions, and Roth conversions — have specific eligibility requirements and tax implications that vary based on individual circumstances. Consult a qualified CPA, tax attorney, or financial advisor before implementing any tax strategy.