After a lifetime of hard work and financial savvy, the last thing high-income individuals want is to see their lifestyle and spending potential eroded by taxes. Thinking about a $5M pre-tax portfolio being worth $3.4M in spending power after-tax at a 32% marginal rate (very simplified) is a tough pill to swallow.

It’s no wonder we look for hacks and strategies to minimize taxes in the short and long-term. Enter the “mega backdoor Roth” – a strategy that, on the surface, seems like an excellent solution to build-up more retirement savings while offering long-term tax benefits. The theory is great, but in reality, it isn’t a no-brainer.

If you’ve heard the buzz and are wondering if it’s the right fit for your wealth plan, here’s the breakdown of what a mega backdoor Roth is and why you may struggle to implement one.

What is a Mega Backdoor Roth?

For 2026, single filers with a Modified Adjusted Gross Income (MAGI) of $168,000+ and joint filers with a MAGI of $252,000+ are not eligible to contribute to a Roth IRA. That’s a problem for high-income earners who want to take advantage of the tax benefits inherent to a Roth IRA – mainly tax-deferred earnings that become tax-free when withdrawn in retirement.

On the surface, the mega backdoor Roth sounds like the solution.

The mechanics seem simple (this is a very simplified explanation):

• Make an after-tax contribution to your 401(k) plan (this is different from making a Roth 401(k) contribution, read on for more details on this)
• Convert the after-tax contribution and earnings within the 401(k) plan to Roth or complete a rollover of the after-tax contribution to a Roth IRA. There are some tax issues to be aware of related to earnings and pre-tax amounts, which we’ll talk more about.

Why would someone do a mega backdoor Roth? The mega backdoor Roth not only solves for the income limitations associated with Roth IRA contributions (there are no income restrictions or income ceilings for after-tax 401(k) contributions), it also allows you to contribute significantly more than a Roth IRA or even a Roth 401(k).

A major benefit of making after-tax contributions to the 401(k) is that you can contribute more than the “elective deferral” amount that is permitted for pre-tax or Roth contributions inside of a 401(k).

Under the after-tax umbrella, you can contribute up to $72,000 for 2026 with an extra $8,000 for those ages 50–59 or 64 and older (and up to $11,250 for those ages 60–63, thanks to the SECURE 2.0 Act “super catch-up”). If you also receive employer matches or made elective pre-tax or Roth deferrals, you will need to subtract those from the overall amount you can contribute after-tax to the 401(k).

Ultimately, after-tax contributions can allow you to sock away significantly more than the $24,500 permitted in 2026 as a Roth 401(k) elective deferral ($32,500 for those 50 and older, or up to $35,750 for those ages 60–63) or the $7,500 permitted in 2026 as a Roth IRA contribution ($8,600 for those 50 and older), all without any income restrictions or limitations.

Because the contributions are made on an after-tax basis, you should not owe income taxes on those contributions when you distribute them in the future. However, earnings on those after-tax contributions inside of the 401(k) are only tax-deferred, not tax-free. The sooner you convert those contributions to the Roth source in the 401(k) or roll them over to a Roth IRA, the more time the earnings will have to compound tax-deferred inside of a Roth vehicle, where distributions in retirement may be tax-free.

Sounds great, right?

Unfortunately, The Mega Backdoor Roth Rarely Works

While it sounds good in theory to get these tax-free investment earnings in retirement, the truth is that the mega backdoor Roth rarely works.

There are two main reasons for this: plan limitations and practical constraints. Let’s take a closer look at why this may not be feasible or the right move for you.

Plan Limitations & Tax Challenges

Plan limitations set the groundwork for mega backdoor Roth plans to fail. All the stars have to align for you to convert your 401(k) to a Roth retirement savings account, and that starts with the type of contributions your employer allows.

First, you need to be able to make contributions on an after-tax basis – and not all workplace retirement plans permit this. A 2022 study by Plan Sponsor Council of America report found that only 21% of 401(k) plans allow after-tax contributions.

Second, the retirement savings plan must allow in-plan conversions and/or in-service withdrawals, which are necessary steps to get your after-tax contributions to a dedicated Roth savings account. Approximately 60 percent of plans offer these in-service conversions, but in-service withdrawals may be more limited.

If you will be converting in plan, your earnings attributable to after-tax contributions will be taxed as ordinary income when doing the conversion, much like a Roth conversion in an IRA. The sooner you can convert the better to minimize your tax burden.

If in-service withdrawals are allowed and you elect to withdraw the after-tax contributions to roll them into a Roth IRA, the pre-tax earnings can be moved to a Traditional or Rollover IRA to continue deferring taxes. One thing to be aware of: it is unlikely that you will be able to just move your after-tax contributions and earnings. IRS rules require you to withdraw both pre-tax and after-tax dollars proportionally when making a partial withdrawal from a retirement account. This doesn’t mean you have to pay taxes on the pre-tax amounts at the time of the withdrawal – you just have to be careful about withdrawing the correct amount of each source and rolling the pre-tax amounts into a Traditional or Rollover IRA.

With that said, in-service distributions will have rules that vary from plan to plan. Most will allow in-service withdrawals after age 59½, which is a significant limitation. Even if a plan allows for after-tax contributions and in-plan conversions, the specific design and administrative processes of the plan might make the execution cumbersome.

Practical Constraints

In addition to the limitations of the plan itself, there are some other practical constraints to weigh when it comes to considering a mega backdoor Roth strategy.

The first is limited investment choices in a 401(k) plan. While most plans will have an extensive array of mutual funds to choose from, there may be asset classes or investment choices outside of a 401(k) plan that would contribute meaningfully to a diversified portfolio and wealth creation over time.

The second limitation is cash flow. While cash flow itself isn’t likely a factor for a high-income earner, you do need to have enough spare cash to fully fund retirement accounts beyond the deferral limits, which may impact other short-term goals. It’s also important to consider that not all compensation is in the form of cash – high-income earners may very well have equity compensation and require much of their cash compensation for their basic living expenses.

Keep in mind that after-tax contributions are considered taxable income, unlike pre-tax contributions which reduce your taxable income. Be sure to have cash on hand or withhold enough from your pay to account for this!

The key here is balancing your short-term and long-term goals. If you’re allocating more funds to long-term goals by maximizing after-tax contributions, you may not have the funds necessary for more immediate goals. Careful cash flow planning and projections can help you understand if this is a feasible strategy for you based on your unique situation and priorities.

Alternatives and Strategies for High-Net-Worth Individuals Saving for Retirement

A mega backdoor Roth is just one solution for retirement savings that you can leverage to enjoy tax savings in retirement. Other strategies allow you to maximize your income and start to grow a nest egg for your later years.

Here are three alternatives and strategies to consider:

Roth Conversions and Partial Conversions

If you’ve already accumulated significant funds in pre-tax accounts, especially IRAs, you can start to chip away at the future tax burden of distributions by doing Roth conversions now.

Tax policy will always be a great uncertainty during a lifetime. Acting on what you know to be true right now, rather than agonizing over future possibilities, can provide peace of mind and real tax savings over your lifetime.

A word of warning when completing Roth conversions: if you have made after-tax contributions to your IRA accounts, you can’t just convert those. Similar to the in-service withdrawals from a 401(k) discussed previously, a proportional amount of pre-tax and after-tax funds will need to be converted.

Roth 401(k) Contributions

If a mega backdoor Roth isn’t the right fit for your retirement saving and investing strategy, then you may consider a Roth 401(k) contribution instead. The main drawback is that contribution limits are smaller than after-tax contributions (in 2026, $24,500 for individuals under age 50, with $8,000 more for those 50–59 or 64 and older, and up to $11,250 for those ages 60–63).

Still, it’s a great way to build after-tax wealth without the income limitations of a Roth IRA.

Tax Planning

The amount you owe to Uncle Sam and the IRS at the end of the year can have a substantial impact on your overall portfolio and cash flow, and it’s easy to feel a lack of control over the situation if you aren’t planning well in advance of December 31st.

When it comes to tax planning, the key word is “planning.” Looking ahead to design a holistic tax strategy that considers the full picture (short-term, long-term, and everything in between) can result in significant savings on your tax returns beyond just the savings you will see with maximizing Roth dollars in your portfolio. Are you being tax efficient with your investments outside of your tax-deferred retirement account? Are you maximizing your deductions and credits, and managing income where possible to ensure you are eligible for as many tax breaks as possible?

While you can do some of the heavy lifting on your own, it’s best to consult with a tax expert who can provide perspective on the bigger picture and point out opportunities you may be missing.

Sharpen Your Tax Game with Monument Wealth Management

A mega backdoor Roth can be a powerful move—but it’s not the right fit for every situation or every plan. If your 401(k) doesn’t allow it, or the math just doesn’t work given where you are right now, that’s not a dead end. It’s a decision point. There are other strategies and tools worth exploring, and the right path forward depends on your full financial picture.

That’s exactly the kind of complexity we show up for at Monument. Whether you’re navigating executive compensation, business ownership, or a financial life that’s simply gotten more layered over time, we come to the table prepared—with options, not just answers.

If you’re wondering whether a mega backdoor Roth—or something else entirely—belongs in your wealth strategy, let’s talk.

Schedule your complimentary wealth check for an assessment!