Backdoor Roth IRA: Avoiding the Pro-Rata Trap

The strategy is simple only when the IRA balance sheet is clean. One overlooked rollover, SEP, or SIMPLE IRA can turn an expected tax-free conversion into a taxable event.

July 23, 2026

For a high-income household, the appeal of a backdoor Roth IRA is easy to understand. The Roth offers tax-free qualified withdrawals and no lifetime required minimum distributions for the original owner,³ but the income limits on direct Roth contributions can close the front door. In 2026, direct Roth eligibility phases out from $153,000 to $168,000 of modified adjusted gross income for single filers and from $242,000 to $252,000 for married couples filing jointly. The combined annual contribution limit for traditional and Roth IRAs is $7,500, or $8,600 for someone age 50 or older.¹

The backdoor Roth uses two separate rules. A taxpayer with compensation may make a nondeductible contribution to a traditional IRA, subject to the annual contribution limit,^1,3 and the IRS permits a traditional-to-Roth conversion regardless of adjusted gross income.² The contribution goes through the traditional IRA "hallway" and into the Roth IRA. That sounds mechanical, and often it is. The problem is that the tax code does not let us label one traditional IRA dollar "after-tax" and another "pre-tax" when money leaves the IRA system.

That is where the pro-rata trap lives.

"Backdoor Roth" is planning shorthand, not a separate account type. The taxpayer first makes a traditional IRA contribution and elects not to deduct it. That nondeductible contribution creates tax basis. The taxpayer then converts traditional IRA dollars to a Roth IRA and reports both the contribution and the conversion on Form 8606. The IRS uses that form to determine how much of the conversion is a return of after-tax basis and how much is taxable income.³

When the taxpayer has no other traditional, traditional SEP, or traditional SIMPLE IRA money, the result can be clean. Assume a taxpayer under age 50 contributes $7,500 for 2026, claims no deduction, and converts the $7,500 before it earns anything. The IRA pool contains $7,500 of basis and no pre-tax money, so the conversion is generally nontaxable. If the account earns a small amount before the conversion, that growth is pre-tax and is generally taxable when converted.³ The objective is not to manufacture a zero-dollar tax return; it is to avoid mixing a small amount of new basis with a large pool of old pre-tax IRA money.

Figure 1 compares the 2026 IRA contribution limits for taxpayers below and above age 50. The $1,100 catch-up is available beginning at age 50, bringing the maximum combined traditional-and-Roth IRA contribution to $8,600.¹

Figure 1: The 2026 combined traditional-and-Roth IRA limit is $7,500, plus a $1,100 catch-up beginning at age 50.

For Form 8606 purposes, the IRS generally treats all of a taxpayer's traditional IRAs as one combined account. In this context, "traditional IRA" generally includes traditional SEP and traditional SIMPLE IRAs. It does not matter that the nondeductible contribution went into a newly opened IRA with a zero balance. A pre-tax rollover IRA at another institution is still part of the same taxpayer's aggregate IRA pool.³

The calculation is also broader than a quick glance at the account after the conversion. Form 8606 uses the taxpayer's year-end value in all traditional IRAs, plus relevant distributions and Roth conversion amounts during the year, to determine the ratio of after-tax basis to the total IRA pool. That is why converting the new contribution and leaving an old rollover IRA untouched does not isolate the new dollars. The December 31 snapshot and the year's conversion activity put the pieces back together.³

Employer qualified-plan balances are different. A regular 401(k), 403(b), or governmental 457(b) balance is not entered as a traditional IRA balance on Form 8606. That distinction creates a planning opportunity: an employer plan may accept a rollover of otherwise taxable traditional IRA dollars, although the plan is not required to accept it.⁴ The goal is to move eligible pre-tax IRA money out of the IRA aggregation calculation while preserving the after-tax basis that can be converted.

The aggregation rule applies separately to each spouse. A married couple does not combine both spouses' IRAs on one Form 8606; each spouse who is required to file uses a separate form.³ One spouse may therefore have a clean backdoor Roth opportunity while the other spouse has a pro-rata problem.

Let's look at the trap with real numbers. Assume Jordan is under age 50, cannot make a direct Roth contribution because of income, and already owns a traditional rollover IRA worth $67,500. Jordan makes a $7,500 nondeductible traditional IRA contribution for 2026 and promptly converts $7,500 to a Roth IRA. Assume no investment gain or loss, no other IRA distribution, and a $67,500 traditional IRA balance on December 31.^1,3

Jordan's total IRA pool for the pro-rata calculation is $75,000: the $67,500 year-end traditional IRA balance plus the $7,500 conversion. Jordan's after-tax basis is $7,500. The nontaxable percentage is therefore 10 percent.³

After-tax percentage = $7,500 / $75,000 = 10 percent.

Tax-free portion of the conversion = $7,500 x 10 percent = $750.

Taxable portion of the conversion = $7,500 - $750 = $6,750.³

Jordan converted $7,500 but did not convert "the" $7,500 nondeductible contribution. Under the pro-rata rule, Jordan converted a slice of the entire IRA pool. Only $750 is treated as a return of basis, while $6,750 is taxable as ordinary income. The unused $6,750 of basis remains associated with Jordan's traditional IRAs and carries forward for future Form 8606 calculations.³

Figure 2 shows the difference between the clean case and Jordan's pro-rata case. Both taxpayers convert the same $7,500. In the clean case, the full amount is basis. In Jordan's case, 90 percent of the converted amount is taxable because 90 percent of the aggregated IRA pool is pre-tax.³ The transaction still creates Roth assets, but it is not the low-tax backdoor conversion Jordan expected.

Figure 2: With $67,500 of pre-tax IRA money, only $750 of a $7,500 conversion is tax-free in this example.

The first step is an IRA inventory, not a contribution. Before moving money, add up every traditional, rollover, traditional SEP, and traditional SIMPLE IRA owned by the taxpayer. Review any prior Forms 8606 for unused basis. Then project what those accounts will hold on December 31 of the conversion year. A new zero-balance IRA does not solve an aggregation problem elsewhere.³

If pre-tax IRA money exists, there are three practical paths. The first is to roll eligible pre-tax IRA dollars into a current employer plan that accepts incoming rollovers. IRS guidance allows otherwise taxable traditional IRA amounts to move into a qualified plan, and a special rule can treat the rollover as coming from pre-tax dollars first when sufficient basis remains outside the plan.⁴ This is often the cleanest solution, but the employer plan's investment menu, expenses, distribution rules, and acceptance procedures still matter. The rollover should be completed with enough time to confirm the year-end IRA balance rather than assuming paperwork will clear on December 31.

The second path is to convert the existing pre-tax IRA balance to Roth and intentionally recognize the taxable income. That can be reasonable when the balance is modest, the current marginal rate is attractive, and the taxpayer can pay the tax from cash outside the IRA. It can be a poor decision when a large conversion pushes income into a meaningfully higher bracket or creates other tax consequences. A backdoor Roth should not become the excuse for an oversized Roth conversion.

The third path is to skip the backdoor contribution for that year. There is no prize for forcing a strategy into a balance sheet that does not support it. Tax-aware planning is not tax-driven planning. If the employer plan will not accept a rollover and a full conversion is unattractive, directing savings to the workplace plan or a taxable account may be the more disciplined choice.

Once the IRA structure is clean, execution matters. Make the contribution for the intended tax year, retain documentation that it was nondeductible, complete the conversion, and make sure Form 8606 is filed with the return. Reconcile the Form 1099-R reporting the conversion and the Form 5498 reporting IRA activity.⁵ Most importantly, do not assume that a tax-preparation program knows the taxpayer's historical basis unless the prior Forms 8606 were carried forward correctly.³

The strongest candidate is a taxpayer whose income is too high for a full direct Roth contribution, who has compensation to support the IRA contribution, and who expects to have little or no pre-tax traditional, SEP, or SIMPLE IRA money in the year of conversion.^1,3 Someone with pre-tax IRA assets may still be a good candidate if a quality employer plan accepts an incoming rollover or if a deliberate taxable conversion already fits the broader multi-year tax plan.⁴

The strategy is a weaker fit for someone with a large pre-tax IRA balance, no employer plan willing to accept it, and no desire to recognize conversion income. It can also be unnecessary for a taxpayer who remains eligible to contribute directly to a Roth IRA. The backdoor is a route around the direct-contribution income limit, not a better version of a direct Roth contribution.

What does this mean for your plan? I view the backdoor Roth as an annual process embedded inside a multi-year retirement-account strategy. The contribution itself is small relative to the balance sheet of many high-income families, but repeated contributions can build a meaningful tax-free reserve. The value comes from executing the strategy cleanly, preserving the tax records, and coordinating the IRA decision with workplace-plan rollovers and larger Roth-conversion opportunities.

This is the framework; the specifics are a conversation with your CPA and Perissos. The pro-rata result depends on account ownership, historical basis, year-end values, other distributions, and the exact sequencing of the transactions. Those facts should be modeled before money moves.

A backdoor Roth IRA is not complicated because it has many steps. It is complicated because one of those steps looks beyond the account being converted and measures the taxpayer's entire traditional IRA balance sheet. That is the trap: the investor sees a clean new account, while Form 8606 sees every traditional, SEP, and SIMPLE IRA together.

The takeaway is straightforward. Inventory first, solve the pro-rata issue second, contribute and convert third, and document the basis all the way through the tax return. Our team will continue coordinating these decisions with the broader retirement and tax plan so the strategy does what it was intended to do.

All my best,

Brandon VanLandingham, CFA, CMT, CFP

Founder / CIO

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[1] Internal Revenue Service, 401(k) limit increases to $24,500 for 2026, IRA limit increases to $7,500 (November 13, 2025), https://www.irs.gov/newsroom/401k-limit-increases-to-24500-for-2026-ira-limit-increases-to-7500. The IRS lists the 2026 IRA contribution limit, age-50 catch-up amount, and Roth IRA income phase-out ranges.

[2] Internal Revenue Service, Topic No. 309, Roth IRA Contributions, https://www.irs.gov/taxtopics/tc309. The IRS states that a taxpayer may be able to convert traditional IRA amounts to a Roth IRA regardless of adjusted gross income.

[3] Internal Revenue Service, Instructions for Form 8606 (2025), https://www.irs.gov/instructions/i8606, and Form 8606 (2025), https://www.irs.gov/pub/irs-pdf/f8606.pdf. These are the latest Form 8606 instructions available as of July 17, 2026. They explain IRA basis, the inclusion of traditional SEP and traditional SIMPLE IRAs, the December 31 value input, conversion reporting, and separate filing for each spouse.

[4] Internal Revenue Service, Publication 590-A (2025), Contributions to Individual Retirement Arrangements, https://www.irs.gov/publications/p590a. The IRS explains that otherwise taxable traditional IRA amounts may be rolled into a qualified plan if that plan accepts the rollover and describes the special ordering rule when IRA basis exists.

[5] Internal Revenue Service, Instructions for Forms 1099-R and 5498 (2026), https://www.irs.gov/instructions/i1099r. The instructions cover reporting of Roth IRA conversions and IRA contribution activity.

This piece is educational. It is not legal, tax, or accounting advice and is not a recommendation to take or refrain from any specific action. Tax law is fact-specific and changes regularly. Please coordinate any decisions discussed here with your attorney, your CPA, and Perissos before acting.

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