{"post":{"slug":"in-plan-roth-conversions-2026","title":"In-Plan Roth Conversions: Converting Without Leaving the 401(k)","excerpt":"You can convert traditional balances to Roth inside your workplace plan, if the plan allows it. It works like an IRA conversion with one important difference nobody mentions.","category":"finance","date":"January 11, 2026","author":"ByteLedger Team","content":"<span class=\"dropcap\">C</span>onverting traditional retirement money to Roth is usually discussed as an IRA operation. Many workplace plans allow it directly, without rolling anything out — an in-plan Roth conversion or rollover.\n\nThe mechanics resemble an IRA conversion: you pay ordinary income tax on the converted amount now, and future qualified withdrawals come out tax-free.\n\n## What changed in 2026\n\n- **Plan adoption continued to rise.** More employers added the feature, though it remains far from universal.\n- **After-tax contribution routes stayed prominent.** The mega backdoor approach kept driving interest in in-plan conversions.\n- **Recharacterisation stayed eliminated.** Conversions remained irreversible, which raised the stakes on timing.\n- **Threshold interactions got more attention.** The knock-on effects of a conversion on other income-tested items became better understood.\n\n## The two things being converted\n\nThe tax consequence depends entirely on which money you convert.\n\n**Traditional pre-tax balances.** Contributions and earnings never taxed. Converting means paying ordinary income tax on the full amount now. This is the standard conversion decision — pay now at a known rate rather than later at an unknown one.\n\n**After-tax contributions.** Some plans allow contributions beyond the standard limit on an after-tax basis, distinct from Roth contributions. Those dollars were already taxed, so converting them to Roth costs tax only on any earnings that accumulated since contribution.\n\nThat second case is the substance of the mega backdoor strategy: contribute after-tax, convert promptly so earnings are minimal, and end up with a large Roth balance for very little additional tax.\n\nThe key detail is **converting promptly**. Earnings on after-tax contributions are taxable at conversion, so leaving them to grow before converting creates a bill. Plans offering automatic conversion of after-tax contributions remove that problem entirely — see [mega backdoor Roth](/blog/mega-backdoor-roth-2026).\n\n## Pay the tax from outside\n\nThe rule that most affects whether a conversion is worthwhile.\n\nIf you use converted funds to pay the tax, you have reduced the amount that ends up in the Roth account and, if you are under the relevant age, potentially triggered an early distribution penalty on the withheld portion.\n\nPaying from taxable savings means the full converted amount lands in the Roth and grows tax-free. That difference compounds over decades and is frequently what determines whether a conversion pays off.\n\nThe practical consequence: **a conversion is most attractive when you have cash outside retirement accounts to pay the tax.** Without it, the case weakens considerably.\n\n## Modelling the year\n\nA conversion adds income, and income has knock-on effects beyond the bracket it lands in.\n\n| Effect | Consequence |\n| --- | --- |\n| Higher marginal bracket | Conversion taxed at a higher rate |\n| Medicare surcharge thresholds | Higher premiums, two years later |\n| Net investment income tax | Can expose other investment income |\n| Credits and deductions phasing out | Effective rate above nominal |\n| Capital gains thresholds | Gains taxed at a higher rate |\n\nThose combine into an effective cost frequently above the headline bracket. Modelling a conversion by bracket alone understates it, sometimes substantially — see [Medicare IRMAA](/blog/medicare-irmaa-explained-2026) and [net investment income tax](/blog/net-investment-income-tax-2026).\n\nThe corollary is that **partial conversions across several years** frequently beat one large one. Converting an amount that fills your current bracket without spilling into the next, repeated annually, spreads the tax at a lower rate.\n\nThe years between retiring and starting Social Security or required distributions are frequently the best window, because income is temporarily low and the brackets are unusually available.\n\n## Common mistakes\n\n- **Paying the tax from converted funds.** Reduces the benefit and may trigger a penalty.\n- **Converting in a peak-income year.** Highest possible rate.\n- **Ignoring threshold effects.** Effective cost above the bracket.\n- **Leaving after-tax contributions to grow before converting.** Creates taxable earnings.\n- **Assuming the plan allows it.** Many do not.\n- **Expecting to undo it.** Conversions are irreversible.\n- **Converting everything at once.** Partial conversions across years are usually better.\n\n## FAQ\n\n**Is this the same as a Roth IRA conversion?**\nThe tax treatment is similar; the account is different. In-plan keeps the money in the workplace plan, which may have better creditor protection and worse investment options than an IRA.\n\n**Can I convert if I am still working?**\nIf the plan permits in-plan conversions, generally yes — you do not need to have separated from service. Plan rules govern.\n\n**What about the five-year rule?**\nConverted amounts have their own holding requirement before earnings can be withdrawn tax-free. Each conversion starts its own clock, which matters if you may need the money.\n\n**Should I convert or contribute to Roth directly?**\nDifferent questions. Direct Roth contributions are simpler; conversions address balances you already have. Both may apply — see [traditional vs Roth 401(k)](/blog/traditional-vs-roth-401k-2026).\n\n## Where to go next\n\nFor the after-tax contribution route, read [mega backdoor Roth](/blog/mega-backdoor-roth-2026). For the threshold effects to model, [Medicare IRMAA](/blog/medicare-irmaa-explained-2026) and [net investment income tax](/blog/net-investment-income-tax-2026).\n\nThis is general information, not tax advice. Conversions are irreversible and plan rules vary; consult a qualified professional.","hue":278,"metaTitle":"In-Plan Roth Conversions: Converting Inside a 401(k)","metaDescription":"How in-plan Roth conversions work, why paying tax from outside the plan matters, and how after-tax contributions enable low-tax conversions.","keywords":["in plan roth conversion","roth 401k conversion","after tax contributions","mega backdoor roth","conversion tax","retirement plan features","roth strategy","retirement planning 2026"],"tldr":["**The plan must permit it** — this is a plan feature, not a universal right.","**You owe tax on the converted amount in that year** — and should pay it from outside the plan.","**Conversions cannot be undone** — recharacterisation of conversions was eliminated.","**After-tax contributions convert with little tax** — which is the mega backdoor route.","**Skip:** converting in a high-income year without modelling the bracket and threshold effects."],"readTime":"4 min read","wordCount":834},"related":[{"slug":"mega-backdoor-roth-2026","title":"Mega backdoor Roth in 2026: how to get an extra $43,500 into a Roth","excerpt":"The mega backdoor Roth lets some workers move tens of thousands into a Roth account beyond normal limits. 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