After-Tax 401(k) Money: Splitting It at Rollover for a Tax-Free Roth

If your 401(k) accepted after-tax contributions (not Roth contributions, but after-tax non-Roth money), you may be sitting on a tax-free conversion opportunity that disappears the moment you mishandle the rollover. This page explains exactly how the split works, what the IRS permits, and what you need to hand the receiving custodian.

What IRS Notice 2014-54 Actually Says

Before 2014, the IRS took the position that any distribution from a 401(k) had to be allocated proportionally between pre-tax and after-tax dollars. That meant you could not cherry-pick: if 15% of your account was after-tax, then 15% of every dollar you moved was after-tax, regardless of where it went.

Notice 2014-54 changed that. When you take a single distribution at separation, you can now direct the two components to different destinations. The after-tax contributions go directly to a Roth IRA, with no tax due because those dollars were already taxed when you contributed them. The earnings that grew on top of those after-tax contributions, which are pre-tax in character, roll to a Traditional IRA. Clean, legal, and efficient.

The mechanics matter. This only works as a direct rollover (or a 60-day rollover where you move both pieces within the window). The plan must issue a single distribution that you then instruct to two separate custodians, or two separate accounts at the same custodian. The plan administrator sends you a 1099-R; Box 5 will show the after-tax amount. That figure is what moves to the Roth. Everything else moves to the Traditional IRA.

Rules, Tradeoffs, and Watchouts

The most common mistake is letting the plan default. Most 401(k) administrators will roll the entire balance to a single Traditional IRA unless you give them explicit written instructions. Once the money lands in a Traditional IRA, the after-tax basis is still yours, but using it requires tracking it through Form 8606 for years. You lose the clean Roth conversion at no cost.

A few rules worth knowing:

• The after-tax amount must be accurately documented. The plan administrator tracks your basis. Request a statement of your after-tax contribution balance before initiating anything.
• Earnings on after-tax contributions are pre-tax. This surprises people. You put in after-tax dollars, those dollars grew, but the growth is ordinary income when distributed. Only the contributions themselves move to Roth tax-free.
• The Roth IRA receiving the rollover does not need to satisfy the five-year rule to be a valid destination. But the five-year clock for tax-free earnings distributions starts the year the Roth IRA was first opened, which is worth knowing if you do not already have one.
• Some plans commingle after-tax and Roth 401(k) contributions in the same subaccount. Those are not the same thing. Roth 401(k) contributions roll to a Roth IRA separately and the entire balance (contributions plus earnings) moves tax-free. After-tax non-Roth contributions are what Notice 2014-54 addresses.
• You must be separated from service, or otherwise eligible for a distribution, for this to apply. This is not an in-service conversion.

How This Differs from the Mega Backdoor Roth

High earners often hear about the mega backdoor Roth as an in-service strategy: contribute after-tax dollars to a 401(k) and then convert or distribute them to a Roth IRA or Roth 401(k) while still employed. That requires the plan to permit in-service withdrawals or in-plan Roth conversions, which many plans do not allow.

The split rollover under Notice 2014-54 is different. It happens at separation, when you are leaving the employer anyway. The plan does not need to support in-service distributions. You simply direct the distribution correctly on your way out the door.

Consider a practical example. You leave a job with $400,000 in your 401(k). Of that, $60,000 is after-tax contributions and $18,000 is earnings on those after-tax contributions. Pre-tax 401(k) contributions and their earnings total $322,000. At rollover, you instruct the plan administrator to send $60,000 to your Roth IRA (no tax owed) and $340,000 to your Traditional IRA ($18,000 of that is the pre-tax earnings on after-tax money). You owe no tax on the $60,000 because it was already taxed. You have now funded a Roth IRA with money that was otherwise locked in a tax-deferred account, and you did it without writing a check to the IRS.

This strategy applies if your plan accepted after-tax contributions and you have accumulated a meaningful after-tax balance. It does not apply if your plan only took pre-tax and Roth 401(k) contributions, or if your after-tax balance is small enough that the administrative effort outweighs the benefit.

How This Connects to the 401(k) Rollover Decision

The split rollover is one specific maneuver within a broader set of choices you face when you leave an employer. For the full picture, including when to leave money in the plan, when to roll to an IRA, and the rules that quietly cost people thousands, see our parent guide: 401(k) Rollover: A Complete Guide to Moving an Old Retirement Account.

In terms of the Sporos Doctrine, this maneuver lives squarely in the Soil layer, the tax architecture stage of the plan. Moving after-tax dollars into a Roth IRA at no tax cost reshapes the long-term structure of your portfolio in a way that compounds for decades. A 7% return inside a Roth IRA is not the same 7% return inside a Traditional IRA. Getting the tax location right at the point of separation is one of the highest-leverage decisions in the entire rollover process.

Frequently Asked Questions

Does my plan have to allow this?

The plan does not need to explicitly allow it. Notice 2014-54 is federal guidance that applies to any qualified plan distribution. What the plan does need is a record of your after-tax contribution basis. Ask the plan administrator or HR for a statement before you initiate the rollover.

What paperwork does the receiving Roth IRA custodian need?

The custodian needs to know the amount and that it is a direct rollover of after-tax 401(k) contributions. Provide a copy of the 1099-R (Box 5 shows the after-tax amount) and request that they code it correctly. Some custodians have a specific rollover contribution form with a field for this. Confirm in writing; do not assume a phone call is enough.

Can I roll after-tax 401(k) money into an existing Roth IRA?

Yes. The rollover does not require a new Roth IRA. It goes into whatever Roth IRA you designate. If you do not yet have a Roth IRA, you will open one. Note that a rollover contribution is not a regular annual contribution, so it does not count against the $7,000 (2024) annual Roth IRA limit.

What if I already rolled everything into a Traditional IRA?

The after-tax basis does not disappear. You track it using Form 8606 and report it each year until you convert or withdraw. The basis reduces the taxable portion of future distributions or conversions. It is less clean than the split rollover, but it is not lost.

Is this the same as a backdoor Roth IRA?

No. The backdoor Roth involves making a non-deductible Traditional IRA contribution and then converting it. This strategy involves rolling existing after-tax 401(k) money directly to a Roth IRA at separation. Same result in spirit (after-tax dollars in a Roth), different mechanism and different scale.

What to Do Next

1. Request a statement of your after-tax 401(k) contribution balance from your plan administrator before you initiate any distribution.
2. Contact both the receiving Roth IRA and Traditional IRA custodians in advance and confirm they can accept a split rollover under Notice 2014-54.
3. Submit written rollover instructions to your plan administrator specifying the exact dollar amount directed to each account.
4. Keep the 1099-R and all rollover confirmation documents for your tax preparer; the correct reporting on Form 8606 and Form 1040 depends on accurate records.

The information provided is for educational purposes only and does not constitute investment, legal, or tax advice. Tax law changes frequently — verify current rules before acting. Consult with qualified professionals for guidance specific to your situation.