I’ve been maxing out my after-tax 401(k) and converting it to a Roth for 2 years — is this a good strategy?

I’ve been maxing out my after-tax 401(k) and converting it to a Roth for 2 years — is this a good strategy? Roughly 70 million workers actively participate in 401(k) retirement plans, and those plans now hold $10.1 trillion in assets as of year-end 2025. The program, which took shape in the late 1970s, has become one of the premier vehicles for American workers to build a financially secure retirement.

For most employees, contributing to a traditional or Roth 401(k) is more than sufficient. For high earners, though, the standard limits can feel like a starting point rather than a destination. The $24,500 elective deferral limit for 2026 is a threshold that average workers rarely approach, yet for top earners it functions more like a floor.

Even stacking a Roth IRA on top, which caps at $7,500 in after-tax contributions for 2026, does not move the needle much for someone with substantial disposable income to shelter. That gap is precisely why more sophisticated strategies have gained traction among high-earning savers. Canva | Tatsiana Volkava from and designer491 from One of the most powerful of these approaches is the mega backdoor Roth conversion.

The strategy works by first maxing out standard 401(k) contributions, then stacking additional _after-tax_ dollars into the same plan up to the Section 415(c) combined ceiling of $72,000 for 2026. Workers who turn 60, 61, 62, or 63 during the year can go even further: the SECURE 2.0 "super catch-up" provision raises their overall plan cap to $83,250. Those extra after-tax dollars are then rolled into a Roth IRA or, if the plan allows it, converted inside the plan to a Roth 401(k).

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Get your guide here (sponsor) A Roth IRA rollover and an in-plan Roth 401(k) conversion are two sides of the same coin. Both must generally be executed in the same year the after-tax contributions are made. The key difference is custody: one lands in an account you own directly, the other stays inside your employer's plan.