What Is an In-Plan Roth Conversion?
Some 401(k) plans let a participant convert money to Roth status without ever leaving the plan itself.
The short answer
An in-plan Roth conversion allows a participant to move eligible balances already inside a 401(k) — often pre-tax deferrals, vested employer contributions, or after-tax contributions — into the plan’s designated Roth account, without needing to leave the employer or first roll the money into an outside IRA. The converted amount is generally treated as taxable income in the year of the conversion, similar to any other Roth conversion, and grows under Roth rules within the plan afterward. Not every 401(k) offers this feature, and which balances qualify depends entirely on how the individual plan is designed.
Which balances are typically eligible
Plans that offer in-plan Roth conversions don’t always allow every dollar in the account to be converted. Common eligible sources include:
- Pre-tax salary deferrals. The employee’s own contributions that were never taxed going in.
- Vested employer contributions. Matching or profit-sharing money the participant has already earned the right to keep, similar to how 401(k) vesting determines ownership generally.
- After-tax contributions. Money contributed beyond regular deferral limits that wasn’t already pre-tax, sometimes associated with a mega backdoor Roth strategy when a plan supports it.
The tax bill an in-plan conversion triggers
Converting pre-tax money to Roth status inside a plan doesn’t avoid taxation — it accelerates it. The converted amount is added to taxable income for the year of conversion, and because the money often stays inside the plan rather than being distributed in cash, participants typically need to cover the resulting tax bill from other funds rather than from the converted balance itself. This mirrors how an ordinary Roth IRA conversion works from a tax standpoint, even though the money never leaves an employer plan.
How this differs from converting through an outside IRA
An in-plan conversion keeps the money inside the 401(k) the entire time, subject to that plan’s investment menu, fees, and distribution rules, rather than moving it into an IRA with potentially different investment choices, similar to comparing Roth 401(k) and traditional 401(k) treatment more broadly. Some participants instead choose to leave a job and complete a rollover to an outside Roth IRA, which is a related but separate path with its own set of rules for eligibility and timing.
What to weigh before converting
- Current versus expected future tax rate. Whether paying tax now makes sense depends on how current tax circumstances compare with what might apply later, which nobody can know with certainty.
- Ability to pay the tax bill from other money. Using converted retirement funds themselves to pay the tax generally reduces the benefit of converting in the first place.
- Plan-specific rules and fees. Some plans limit how often a conversion can be done or which balances qualify, so the plan document is the source for specifics rather than general assumptions.
The takeaway
An in-plan Roth conversion offers a way to shift taxation earlier on eligible 401(k) balances without leaving the employer’s plan, but it comes with the same fundamental tradeoff as any Roth conversion: paying tax sooner in exchange for different tax treatment later. The rules governing eligibility and taxation can change over time, so checking current plan and tax details is part of understanding how it would actually apply.