EP Wealth Vice President, Advisor, Carrie Sax, CFA, CFP^®, explains how the mega backdoor Roth works and how high earners may use it to build Roth savings beyond standard 401(k) limits. 

Mega Backdoor Roth Options: How They Work and Who They're For

For high earners who have already reached the standard 401(k) contribution limit, a mega backdoor Roth may create another way to build Roth savings through an employer retirement plan. This option makes sense for those who are maxing out their retirement contributions but still have money to save.

The strategy uses after-tax 401(k) contributions, so those contributions do not reduce your taxable income in the year they are made. Instead, the potential benefit comes from moving those after-tax dollars into a Roth account, where future qualified distributions may be excluded from federal taxable income.

When I discuss this strategy with clients, I first look at their employer plan and how much room remains under the annual contribution limit. I also look at whether directing additional cash to retirement accounts fits their other financial priorities.

In this blog, I cover:

• How a mega backdoor Roth works
• The 2026 contribution limits that affect the strategy
• The difference between pre-tax, Roth, and after-tax 401(k) contributions
• How a mega backdoor Roth differs from a regular backdoor Roth IRA
• The plan features you need
• Who may want to consider the strategy

How the Mega Backdoor Roth Works

There are two buckets to the mega back door option. One starts with the contributions you make from your pay. The other reflects contributions from your employer.

For a mega backdoor Roth, however, there is an important third piece: employee after-tax contributions.

Here is the basic sequence:

• You make your regular 401(k) contributions, either pre-tax or Roth.
• Your employer may add matching or other employer contributions.
• If the plan permits it and room remains under the annual limit, you make additional after-tax contributions.
• Those after-tax dollars are then moved to a Roth account.

The last step may happen through an in-plan Roth conversion, which moves eligible funds into the Roth portion of the same workplace plan. Another possibility is an eligible in-service distribution and rollover, which may allow funds to move to a Roth IRA while you are still employed.

These after-tax 401(k) contributions are not deductible.

Timing can be important. Earnings that accumulate on after-tax contributions before they are converted generally have not yet been taxed. Converting after-tax contributions promptly may limit the amount of earnings that could create taxable income during a Roth conversion.

2026 Contribution Limits

Let's look at some concrete numbers to get a better idea of how this works.

For 2026, the standard employee deferral limit for a 401(k) is $24,500. The overall defined contribution limit under Section 415(c) is $72,000, or 100% of compensation if lower. Catch-up contributions are generally outside that $72,000 limit.

2026 401(k) Contribution Limits 

Source: https://www.irs.gov/retirement-plans/cola-increases-for-dollar-limitations-on-benefits-and-contributions

The $47,500 is not automatically available as an employee after-tax contribution. Employer contributions use part of that amount, and the plan itself may place additional limits on after-tax contributions.

A Hypothetical Example

Suppose you are under age 50 and contribute the full $24,500 to your 401(k) in 2026. Your employer contributes another $10,000.

That would bring total contributions to $34,500.

With a $72,000 annual additions limit, up to $37,500 of additional room could remain for after-tax employee contributions if your plan permits them and you meet the other applicable requirements.

Those after-tax dollars could then potentially be converted to Roth within the plan or distributed through an eligible rollover.

*This example is for hypothetical purposes only.

Catch-Up Rules for 2026

People age 50 or older can generally make an additional $8,000 catch-up contribution in 2026 when their plan permits it. Participants who turn 60, 61, 62, or 63 during 2026 have a higher catch-up limit of $11,250.

There is also a new Roth catch-up rule in effect for 2026. If your prior-year wages from the employer sponsoring the plan exceeded $150,000, catch-up contributions generally must be made on a Roth basis when the plan has a Roth feature and offers catch-up contributions.

Pre-Tax, Roth, and After-Tax Contributions

A traditional 401(k) and a Roth 401(k) differ in how they are taxed. But the mega backdoor Roth involves a third category—after-tax contributions—that works differently from both. Here's how the three types compare:

Pre-Tax (Traditional 401(k))

Contributions are deducted from your taxable income in the year you make them. However, once you start making withdrawals, you must pay taxes on those funds. Pre-tax accounts are also subject to required minimum distributions starting at age 73 or 75, depending on birth year.

Roth 401(k)

Contributions are made with after-tax dollars and don't lower your taxable income. Qualified distributions—generally those made after age 59½ and after the account has been open for at least five years—may be withdrawn tax-free. Roth 401(k) accounts are not subject to lifetime required minimum distributions, which means Roth balances can remain in the account and continue to grow.

After-Tax (Non-Roth)

This is the contribution type used in the mega backdoor strategy. Like Roth contributions, after-tax contributions are made with dollars you've already paid income tax on. Unlike Roth contributions, earnings on after-tax dollars are taxable when withdrawn. That's why the conversion step is critical. Once after-tax contributions are converted to Roth, any future growth may be tax-free if the distribution qualifies.

Side-by-side comparison — Pre-Tax vs. Roth vs. After-Tax 401(k) Contributions

Mega Backdoor Roth vs. Regular Backdoor Roth IRA

The mega backdoor Roth and the regular backdoor Roth IRA are separate strategies that serve a similar purpose: getting money into Roth accounts when your income is too high to contribute directly. They work differently, and many people use both.

Regular Backdoor Roth IRA

A regular backdoor Roth generally starts with a contribution to a traditional IRA followed by a conversion to a Roth IRA. It is often considered by taxpayers whose income prevents them from making the full amount of a direct Roth IRA contribution.

For 2026, direct Roth IRA contributions phase out at modified adjusted gross income of:

• $153,000 to $168,000 for single and head-of-household filers
• $242,000 to $252,000 for married couples filing jointly

The IRA contribution limit for 2026 is $7,500, plus a $1,100 catch-up contribution for eligible individuals age 50 or older.

A backdoor Roth IRA also requires attention to the IRA pro rata rules if you hold other pre-tax IRA assets.

Mega Backdoor Roth

A mega backdoor Roth uses an employer-sponsored retirement plan. Its potential contribution amount is tied to the larger Section 415(c) limit and the amount already contributed by you and your employer.

The two strategies operate under separate contribution rules, so some taxpayers may be able to use both in the same year when the applicable requirements are met.

For someone considering either approach, tax planning can help place the current-year tax treatment within the broader retirement strategy.

401(k) Plan Requirements for a Mega Backdoor Roth

Not all employers offer a mega back door Roth. Your 401(k) plan generally needs to support two features:

• After-tax contributions: The plan must allow you to make after-tax contributions to your 401(k). These are separate from Roth 401(k) contributions. Plan rules may also limit how much highly compensated employees can contribute.
• A way to move those contributions to Roth: This may be an in-plan Roth conversion or an eligible in-service distribution that can be rolled into a Roth IRA.

To check your plan, review the summary plan description or benefits portal for terms such as “after-tax contributions,” “in-plan Roth conversion,” and “in-service distribution.” You can also ask the plan administrator which options are available.

Some plans also allow employer matching or nonelective contributions to be made on a Roth basis. This is a separate feature from the employee after-tax contributions used for a mega backdoor Roth.

Who Should Consider a Mega Backdoor Roth

This option makes sense for those who are maxing out their retirement contributions but still have money to save.

I would typically start investigating a mega backdoor Roth when several conditions line up:

You Are Already Reaching the Standard 401(k) Deferral Limit

If you are not yet using the normal employee contribution capacity, that is usually the first part of the 401(k) to evaluate.

Your Employer Contributions Leave Room Under the Annual Limit

A smaller employer contribution can leave room between the contributions already made to the account and the $72,000 Section 415(c) limit for 2026.

That gap may create capacity for voluntary after-tax contributions when the plan allows them.

You Have Cash Flow Available for Additional Long-Term Savings

Money contributed to a retirement plan generally should be viewed as long-term savings. Before directing additional cash to a mega backdoor Roth strategy, I would look at the client's near-term spending needs and emergency reserves.

I would also consider other financial goals that may require accessible funds.

Your Plan Supports the Required Transactions

The strategy cannot be implemented simply because room remains below the IRS limit. Your employer plan has to permit after-tax contributions and provide an appropriate route to Roth.

Could a Mega Backdoor Roth Be Worth Exploring?

A mega backdoor Roth can be useful in the right circumstances, but contribution capacity alone does not determine whether it fits. Retirement planning can help evaluate the strategy alongside cash flow needs and other retirement resources.

If you'd like help evaluating whether the mega backdoor Roth fits within your overall financial plan, EP Wealth advisors can walk you through the details. Reach out to schedule a conversation.

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