On a recent episode of the Catching Up to FI podcast, financial planner Allen Mueller laid out one of the most underused legal tax shelters in the U.S. code. That includes a custodial Roth IRA seeded the moment a child has documented earned income. The math is what makes parents lean forward. $5,000 contributed every year from infancy, assuming a 7% annual return, turns into roughly $3.3 million in a Roth IRA at age 60. Every dollar of that growth is sheltered from federal income tax for life.
The strategy hinges on a structural quirk of the tax code. Minors cannot legally contribute to a Roth IRA without earned income. So Mueller’s plan uses a custodial brokerage account during the early years and then converts it into a window before the IRS would tax the gains heavily.
How Mueller’s Custodial Roth Plan Works
The blueprint, as Mueller described on episode 221 of Catching Up to FI, runs in three phases. First, a parent funds a custodial account for a newborn. As Mueller put it, “Just for a newborn who gets $5,000 contributed to their account every year, at age 18, obviously it turns into an IRA, and then there’s a Roth conversion window.”
Second, once the child ages out of the kiddie tax, the account is converted to a Roth IRA over multiple years to manage the tax bill. Third, you let compounding do the heavy lifting. “If they’ve got a bunch of dollars in Roth at age 26, say the conversions stop, just assuming a 7% annual return, you’re talking about $3.3 million in a Roth IRA at age 60,” Mueller said.
For context on why tax-free matters: the 10-Year Treasury currently yields 4.49%, a benchmark for “safe” taxable returns. A Roth’s compounding edge widens dramatically when those taxable yields are reinvested over six decades.
The Earned Income Requirement Is Non-Negotiable
The IRS allows Roth contributions only up to the child’s actual earned income for the year. It’s capped at the annual contribution limit. The official IRS Roth IRA rules spell out that compensation must come from work, not gifts or investment income. The current ceiling is $7,500 in 2026.
Mueller is blunt about what counts. Household chores do not. “Any income from an outside source does qualify,” he said. Think part-time jobs at 14, raking neighbors’ leaves, tutoring, or paid online surveys. He recommends keeping a logbook with “date it was performed, who the child did it for, and how much they received.”
His own example: Mueller’s 9-year-old daughter earned a couple of hundred dollars completing online surveys about kids’ TV shows, which he documented and deposited into her Roth. Contributions must match real, defensible income. Stuffing a child’s account to the IRS cap without paperwork is the fastest way to invite an audit.
The Conversion Window And The Kiddie Tax Trap
The conversion phase is where most parents stumble. The kiddie tax applies to unearned income above a threshold at the parents’ marginal rate, which can blow up a poorly timed Roth conversion. Mueller’s framework waits until the child is past the kiddie tax age (generally 24 if a full-time student, 19 otherwise) and then spreads conversions across multiple low-income years.
Want to model your own version? Adjust the inputs below to see what a custodial Roth could compound under different contribution and return assumptions.
The calculator above uses Mueller’s 7% return assumption over a 60-year runway. Even cutting contributions in half or shortening the horizon by a decade leaves a seven-figure outcome.
What To Watch Next
Enforcement around documentation on custodial Roth accounts has tightened. Parents executing this strategy should retain pay stubs, 1099s, or signed neighbor invoices for at least seven years. With Gen Z’s average 401(k) balance at just $17,000, families using a custodial Roth give their kids a head start that no employer match can replicate.
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