The Mega Backdoor Roth Move Tech Workers Use to Stuff an Extra $34,000 a Year Into a Roth

"The mechanic hinges on the IRS code section nobody talks about at the kitchen table: 415(c). Most 401(k) coverage stops at the employee deferral limit. The 415(c) total annual additions limit is the real ceiling on what can land inside the plan, and for 2026 the IRS lifted it from $70,000 to $72,000. Everything between the deferral and that ceiling is the opening."

"Walk the stack for the engineer above. The $24,500 employee deferral lands first. A typical large-cap tech match runs 5% to 6% of base, which on a $280,000 salary gets capped quickly; assume the employer kicks in $13,500. That is $38,000 consumed against the $72,000 415(c) cap. The leftover space, $34,000, is exactly what the plan document can let the participant fund as after-tax (not Roth, not pre-tax) contributions."

"Those after-tax dollars are useful only if they leave the after-tax bucket fast. Two routes do the job. An in-plan Roth conversion sweeps the after-tax balance into the Roth side of the same 401(k). An in-service rollover ships it to an outside Roth IRA. Either way, the basis converts tax-free, and from that moment forward the money grows and eventually distributes tax-free."

"Run the engineer's $34,000 annual contribution out 30 years at a 7% return. The future value of that annuity stream lands at roughly $3.21 million, none of which the IRS gets to touch on the way out. That sits on top of the standard deferral, the match, and any taxable brokerage savings the household runs alongsid"

A 401(k) participant can contribute beyond the standard employee deferral limit by using the IRS 415(c) total annual additions ceiling. For 2026, the limit is $72,000, creating room between employee deferrals and employer match for additional after-tax contributions. With a $280,000 salary, a $24,500 deferral plus an estimated $13,500 employer contribution can leave about $34,000 available for after-tax 401(k) contributions, depending on plan rules. Those after-tax amounts can be moved quickly through an in-plan Roth conversion or an in-service rollover to a Roth IRA. The basis converts tax-free, and subsequent growth and qualified distributions can be tax-free. A 30-year projection at 7% on $34,000 per year yields about $3.21 million.

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