In-Plan Roth Conversions Explained

An in-plan Roth conversion is the cleanest execution of the mega backdoor Roth strategy. Rather than withdrawing after-tax contributions from your 401(k) and rolling them externally to a Roth IRA, an in-plan conversion moves the after-tax funds directly into a Roth 401(k) bucket within the same employer plan. This approach minimizes paperwork, eliminates the 60-day rollover window, and allows some plans to fully automate the process. Understanding when your plan offers this feature and how to execute it is essential to making the mega backdoor Roth as painless as possible.

Quick definition: An in-plan Roth conversion transfers after-tax contributions directly from the after-tax bucket of your 401(k) to the plan's Roth 401(k) bucket, with minimal administrative burden and no external rollover required.

Key takeaways

• In-plan Roth conversions move after-tax funds within your employer plan to a Roth bucket, avoiding external rollovers
• Not all plans offer this feature; you must verify it's available before relying on it
• Conversions can happen as frequently as monthly or quarterly, depending on plan rules
• Some plans allow automatic, recurring conversions, making the mega backdoor nearly hands-off
• Only after-tax contributions can be converted in-plan; employer match and employee deferrals typically cannot

The Plan's Roth Bucket: Understanding the Architecture

Many 401(k) plans now offer a Roth 401(k) option, which operates alongside traditional deferrals. Here's how the buckets work:

Traditional 401(k) bucket: This includes your traditional employee deferrals and employer contributions (match, profit sharing). Money grows tax-deferred and is taxable on withdrawal.

Roth 401(k) bucket (if offered): This includes Roth employee deferrals—money you contribute with after-tax dollars, elect as Roth, and which grows tax-free. Withdrawals are tax-free if you're 59½ and the account is 5+ years old. This bucket is distinct and separately accounted for.

After-tax bucket: Money you contribute beyond your deferral limit, not elected as Roth at the time of contribution. This is the "raw material" for the mega backdoor. It grows tax-deferred but is not Roth until converted.

An in-plan Roth conversion moves funds from the after-tax bucket into the Roth bucket. This recharacterizes the funds as Roth, triggering the tax consequences of the conversion (you pay tax on earnings) but locking in the Roth benefits going forward.

How In-Plan Conversions Differ From External Rollovers

The alternative to an in-plan conversion is an external rollover: you withdraw after-tax funds from the plan, then deposit them into a Roth IRA at a brokerage of your choice. Both achieve the same end result—moving funds to Roth—but the paths differ.

In-plan conversion advantages:

• Funds stay within the same plan, no distribution paperwork needed
• No 60-day rollover window to monitor
• Some plans automate it, requiring zero ongoing action
• Typically processed quickly (1–5 business days)
• Your investment options remain the same as the plan's

In-plan conversion disadvantages:

• Limited to the plan's investment options (may be more expensive or limited than opening a standalone Roth IRA)
• Roth 401(k) balance still subject to required minimum distributions (RMDs) at age 73, unlike a Roth IRA
• If you later leave the employer, you'd need to roll the Roth 401(k) to a Roth IRA to escape RMDs

External rollover advantages:

• Full investment freedom at any brokerage (typically lower fees than employer plans)
• Roth IRA has no required minimum distributions, allowing longer tax-free growth
• Broader range of investment options, especially low-cost index funds
• Can consolidate multiple plans into one Roth IRA

External rollover disadvantages:

• Additional paperwork and distribution process
• 60-day rollover deadline creates timing risk
• Requires opening and managing a separate Roth IRA account

For simplicity and automation, in-plan conversions are often superior, especially if your plan offers them. For investment flexibility and long-term optimization, external rollovers to a Roth IRA often win.

Checking Whether Your Plan Allows In-Plan Roth Conversions

Not every plan that offers a Roth 401(k) option allows conversions of other balances. A plan might allow you to make Roth deferrals but prohibit conversions of after-tax or traditional balances. You must verify the plan's specific rules.

How to check:

1. Request a copy of the Summary Plan Description (SPD) from your HR or plan administrator. This document outlines all plan features, including whether in-plan Roth conversions are available.
2. Look for language like "in-plan Roth conversion," "Roth conversion feature," or "conversion to Roth 401(k) bucket."
3. If the SPD is unclear, email your plan administrator directly: "Does our plan allow in-plan conversions of after-tax contributions to the Roth 401(k) bucket?" A simple yes or no is sufficient.

If your plan doesn't allow in-plan conversions: You can still do the mega backdoor, but you'll need to use the external rollover method (withdraw and roll to a Roth IRA).

The Mechanics of an In-Plan Conversion

Once you've confirmed your plan allows in-plan conversions, the process is straightforward.

Step 1: Check your after-tax balance Log into your plan's website or contact HR to see how much you have in the after-tax bucket. If you've only been contributing for a few months, this might be a few thousand dollars. If you're doing this mid-year, the balance includes any earnings accumulated.

Step 2: Request the conversion Visit your plan's website and look for a "conversions" or "Roth conversion request" section. Most plans offer an online portal. If not, email your plan administrator with a request: "I would like to convert $[amount] of my after-tax contributions to the Roth 401(k) bucket."

Be specific about the amount. You can convert the full after-tax balance or a portion. Most people convert everything to simplify taxes, but some prefer converting in increments.

Step 3: Specify earnings treatment Some plans require you to specify whether you're converting just contributions, just earnings, or both. Generally, you'll want to convert both the contributions and earnings together. Splitting them is unnecessary and complicates tax reporting.

Step 4: Confirm the conversion The plan administrator will process your request, typically within 1–5 business days. You'll receive confirmation, often with a Form 1099-R or internal conversion statement showing the amount converted.

Step 5: Update investment allocation (if needed) After the conversion, your funds are in the Roth bucket but may be in a default money-market fund. Log back into the plan website and move the converted funds to your desired investments—typically a target-date fund or diversified portfolio of stock and bond index funds.

Diagram: In-Plan Conversion Process

Timing: When to Execute the Conversion

The timing of your conversion relative to the contribution matters for two reasons: minimizing earnings that become taxable, and simplifying tax reporting.

Conversion timing options:

Monthly conversions: Some plans allow monthly in-plan conversions. If your plan supports this, you can convert as soon as after-tax contributions land in the account (sometimes even in the same paycheck cycle). This minimizes earnings—after-tax contributions sit for only 30 days before converting, so the taxable earnings are minimal.

Quarterly conversions: More common than monthly. You accumulate after-tax contributions for three months, then request a conversion. The taxable earnings are still small, and the administrative burden is manageable.

Annual conversions: Some plans limit conversions to once per year, typically at year-end or immediately after the plan year closes. This is acceptable; just plan for the conversion to happen in January (for the previous year's contributions) or December (for the current year's contributions).

The rule: Conversions should happen in the same calendar year as the contribution to simplify IRS reporting. If you contribute in 2025 and don't convert until 2026, tax reporting becomes complicated. Avoid this.

Best practice: Convert quarterly or more frequently if your plan allows. This spreads the tax bill across multiple Form 1099-Rs, which is often cleaner for tax preparation.

Tax Reporting and the Conversion

When you execute an in-plan Roth conversion, the plan administrator reports it to the IRS via a Form 1099-R, Distribution from Qualified Retirement Plans. The form will show:

• Code "2" for rollover/conversion
• The gross amount converted
• Any federal withholding

What you owe: You owe ordinary income tax only on the earnings portion of the conversion. The after-tax contributions are not taxable (you already paid tax on them). If you convert $30,000 in after-tax contributions plus $1,200 in earnings, you owe tax on the $1,200 at your marginal rate (e.g., 37% if you're a high earner = $444).

Reporting on your tax return: You'll report the conversion on Form 1040. If the plan withholds taxes (which it likely will), those withholdings are applied to your annual tax liability. Many people have the plan withhold 22–37% of the earnings to avoid a surprise tax bill at tax time.

Example: Sarah converts $40,000 in after-tax contributions plus $800 in earnings (total conversion $40,800). She's in a 37% federal bracket plus 8% state = 45% combined. She asks the plan to withhold 45% of the earnings = $360. The remaining $440 in tax on the earnings is paid when she files her return. Total tax cost: $800.

Automatic Conversions and Recurring Features

Some of the largest employers' plans offer automatic in-plan Roth conversions, a game-changing feature for the mega backdoor Roth. Instead of manually requesting conversions, the plan automatically converts all after-tax contributions to Roth on a set schedule—monthly, quarterly, or annually.

How it works:

1. You set up the automatic conversion feature in the plan's portal, specifying the frequency (monthly, quarterly, etc.).
2. Each period, after-tax contributions are automatically moved to the Roth bucket without any further action from you.
3. You receive Form 1099-R notices for each automatic conversion.

Benefit: The mega backdoor becomes completely hands-off. You contribute through payroll, and the plan handles conversions automatically. This eliminates the most common error: forgetting to request the conversion.

Finding automatic conversions: Ask your HR or plan administrator: "Does our plan offer automatic or recurring in-plan Roth conversions?" If yes, ask how to enable it. It's usually a one-time setup in the plan portal.

Real-World Examples

Example 1: Large tech company with monthly automatic conversions Joshua works at a large tech firm that offers monthly automatic in-plan Roth conversions. He has written authorization to contribute $3,500 per month in after-tax dollars (total $42,000 annually). His plan automatically converts these each month. Each month, his $3,500 contribution (plus ~$50 in earnings) moves to his Roth 401(k) bucket. He receives 12 Form 1099-Rs each year, one for each monthly conversion. Annual tax cost: 37% × $600 in total earnings = $222. By year-end, he's moved $42,000 to Roth tax-free, and it continues growing tax-free.

Example 2: Smaller employer requiring quarterly manual requests Mia works at a mid-size consulting firm that allows in-plan Roth conversions but doesn't automate them. She contributes $9,000 per quarter in after-tax dollars. In January, April, July, and October, she logs into the plan portal and requests a conversion of her accumulated after-tax balance. Each quarterly conversion includes ~$400–$500 in earnings (depending on market performance). She pays tax on those earnings, approximately $150 per quarter. By year-end, $36,000 is in her Roth bucket, growing tax-free.

Example 3: Plan requiring annual conversions at year-end David's plan only allows one conversion per plan year, processed in December. He contributes after-tax throughout the year, accumulating $32,000 by December. When December comes, he requests the conversion. At that point, his balance has grown to $32,500 (due to a strong market year and $500 in earnings). He converts the full $32,500, paying tax on the $500 in earnings (~$185 at his 37% rate). The conversion is reflected on his plan statement; the funds are in the Roth bucket and grow tax-free going forward.

Required Minimum Distributions and Roth 401(k)s

A critical limitation of in-plan Roth conversions: Roth 401(k) balances are subject to required minimum distributions (RMDs) at age 73, just like traditional 401(k) balances. Roth IRAs, by contrast, have no RMDs.

If you use an in-plan conversion and keep the Roth funds in the 401(k), you'll have to withdraw a percentage of the balance annually starting at 73, even though the balance is in a Roth account. This can be suboptimal if you don't need the money and want it to continue growing tax-free.

Workaround: When you leave your employer (or at retirement), you can roll the Roth 401(k) to a Roth IRA. Once outside the 401(k), RMDs no longer apply. This is a perfectly legal strategy and is commonly used by people who've built large Roth 401(k) balances via mega backdoor conversions.

Example: By age 65, Elena has accumulated $500,000 in a Roth 401(k) via annual mega backdoor conversions. At age 73, she's forced to withdraw approximately 4% of the balance ($20,000) to satisfy her RMD, even though she doesn't need the money. However, when she retires at 72, she rolls the Roth 401(k) to a Roth IRA. Now RMDs no longer apply, and the $500,000 can continue growing untouched until she actually needs it.

Conversions of Employer Match and Deferrals

One critical limit: you can typically only convert the after-tax contributions bucket in an in-plan Roth conversion. You cannot convert employer match, profit sharing, or your traditional employee deferrals using this method.

Why? IRS rules distinguish between the sources of contributions. After-tax contributions are discretionary and conversion-eligible. Employer contributions and traditional deferrals have their own rules and are not directly conversion-eligible in the same way.

If you want to convert traditional deferrals or match: You'd need to use a separate strategy, called a "non-spousal rollover" or "conversion," which is treated differently for tax purposes and has its own rules. This is more complex and less commonly done because the after-tax conversion space is usually sufficient for most high earners' goals.

Real-World Considerations for Continuing Employees

If you're a continuing employee (not leaving the company), after-tax contributions and in-plan conversions are straightforward—the after-tax bucket exists throughout your employment, and you can convert as often as your plan allows.

However, some plans have quirks:

• Plan-to-plan transfers: If your employer changes plan administrators, the after-tax balance typically transfers with your account. The conversion feature should carry over, but verify with the new administrator.
• Plan amendments: If your plan is amended to disallow after-tax contributions, you cannot contribute further, but existing after-tax balances can usually still be converted.
• Termination of the plan: If your employer terminates the 401(k) plan, you must distribute all balances. You can roll them to an IRA, including converting the after-tax portion to a Roth IRA at that time.

Real-World Examples

Example 1: Tech startup, scale-up scenario Camille joins a startup at year 5, when the company is just setting up its first 401(k). Her employer chooses a modern plan from Fidelity that offers in-plan Roth conversions. Over her first year, she contributes $22,000 in after-tax dollars and requests quarterly conversions. The plan processes these with no friction. By year 10, when the startup is acquired, she's accumulated $220,000 in her Roth 401(k) from mega backdoor conversions alone. When she joins the acquiring company, she rolls the Roth 401(k) to a Roth IRA, giving her investment freedom and eliminating future RMDs.

Example 2: Consulting firm, no automation Tom works at a 50-person consulting firm with a straightforward 401(k) plan from Charles Schwab. In-plan conversions are allowed, but the plan doesn't automate them. Tom contributes $12,000 per quarter in after-tax contributions and emails his HR administrator each quarter to request a conversion. HR passes the request to Schwab, which processes it within a week. By year-end, he's converted $48,000. The process is slightly more manual than fully automated plans, but the outcome is identical: tax-free Roth funds, no external rollover needed.

Common Mistakes

Mistake 1: Assuming the plan offers in-plan conversions without verifying Not all plans allow this feature. Don't contribute after-tax dollars without confirming that in-plan conversions are available. If they're not, you'll either need to use external rollovers or consider whether the mega backdoor is worth it for your situation.

Mistake 2: Converting and forgetting to rebalance the investments After a conversion, your Roth bucket may contain the funds in a default money-market fund or short-term stable value fund. If you don't log back in and rebalance to a more growth-oriented portfolio, your mega backdoor funds earn minimal returns. Actively rebalance to your target allocation after each conversion.

Mistake 3: Not accounting for RMDs later in retirement If you use in-plan conversions and accumulate a large Roth 401(k) balance, remember that RMDs apply. Plan for this; ideally, roll the Roth 401(k) to a Roth IRA when you retire to escape RMDs.

Mistake 4: Missing the annual deadline for conversions if your plan allows only annual processing If your plan allows only annual conversions (e.g., December), mark your calendar. Missing the window means another year before the after-tax contributions are converted, and they accumulate unnecessary earnings and complexity.

Mistake 5: Converting partial after-tax balances and creating a record-keeping nightmare If you have $15,000 in after-tax contributions and request to convert only $10,000, you create a partial-balance scenario. The remaining $5,000 must be tracked separately for future conversion. It's cleaner to convert the full balance each time to simplify tax reporting and account tracking.

FAQ

Q: Can I request an in-plan conversion immediately after contributing after-tax dollars, or must I wait?

A: Most plans allow conversions within days or weeks of contribution. Some plans require contributions to settle first (1–2 business days). A few require waiting until month-end. Check your plan's rules; quarterly or monthly conversions are typical.

Q: If my plan offers both in-plan conversions and allows external rollovers, which should I choose?

A: In-plan conversions are simpler and avoid external rollover paperwork. However, external rollovers to a Roth IRA give you investment flexibility and escape RMDs. For long-term planning, external rollovers are often superior. Consider the in-plan conversion as a stepping stone—do it while employed, then roll to a Roth IRA when you leave.

Q: Does an in-plan Roth conversion reset my five-year Roth clock?

A: If you're converting to a Roth 401(k), each Roth account has its own five-year clock. If you later roll the Roth 401(k) to a Roth IRA, the clock transfers with it. You won't reset—the five-year clock is based on when the first Roth account was opened, not when conversions happen.

Q: What if my plan allows in-plan conversions but I leave the company before converting my after-tax balance?

A: After you leave, you typically have 60 days (or more, depending on plan rules) to roll the after-tax balance to a Roth IRA externally. You cannot perform in-plan conversions once you're no longer an employee. The after-tax bucket doesn't disappear; you just convert it externally as part of your rollover.

Q: If I request an in-plan conversion, can I undo it if the markets drop?

A: No, conversions cannot be undone as of 2018. Once converted, the funds are in the Roth bucket, and you've triggered the tax consequences. This is why timing (early in the conversion to minimize earnings) is important—it reduces taxable income on conversion.

Q: Do after-tax contributions count toward my $24,000 annual deferral limit?

A: No, the $24,000 limit is only for employee deferrals (traditional or Roth combined). After-tax contributions are separate and can be substantially more, up to the $70,000 aggregate limit. Your employer match counts toward the aggregate but not toward your deferral limit.

Related concepts

• 01-what-is-the-mega-backdoor-roth.md — overview and strategy
• 02-how-the-mega-backdoor-works.md — detailed execution steps
• 03-after-tax-vs-roth-vs-traditional.md — tax comparison of strategies
• 05-checking-if-your-plan-allows-it.md — how to verify plan features

Summary

In-plan Roth conversions offer the cleanest path to executing the mega backdoor Roth strategy. By converting after-tax contributions directly within your employer's 401(k) plan, you avoid external rollover paperwork, eliminate the 60-day rollover window, and benefit from potential automation. Not all plans offer this feature, so verification is essential. The primary limitation is that Roth 401(k) balances are subject to required minimum distributions, though you can roll the balance to a Roth IRA when you leave to eliminate RMDs. In-plan conversions work best when combined with frequent (monthly or quarterly) conversion schedules to minimize taxable earnings. Tax rules and plan features are current as of mid-2020s; verify with your plan administrator for your specific situation.

Next

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