Meet Emily, a self-employed 38-year-old cybersecurity consultant who just landed a string of high-profile contracts. Her income has skyrocketed to $450,000 a year, a far cry from her days as a mid-level IT analyst. She’s thrilled but nervous. The stakes are high: she wants to build a robust financial foundation for her family’s future – think early retirement, dream vacations, and a college fund for her two kids. But with great income comes great… taxes. Emily and her husband are in the 35% federal tax bracket, and she’s determined not to let Uncle Sam claim more of her hard-earned cash than she has to. She also doesn’t want to spend her newfound wealth on items that don’t actually matter to her, like a new car every couple of years or designer handbags that will simply collect dust in the closet. It’s tempting because she sees her circle of friends with such items, but Emily doesn’t want to play the game of keeping up with the Joneses.
Enter the Mega Backdoor Roth, a financial strategy that’s like finding a cheat code for tax-advantaged retirement savings. Let’s walk through how Emily can use a Solo 401(k) with a Mega Backdoor Roth to supercharge her savings while keeping her tax bill in check.
Emily’s Financial Wake-Up Call
Emily’s always been frugal, but her new income feels like a double-edged sword. She’s excited about the possibilities—paying off her mortgage early, funding her kids’ education, maybe even retiring by 55 to travel the world with her husband. But her first quarterly tax estimate was a gut punch: nearly 40% of her income was owed to the IRS and state. “I’m working my tail off, and half my money’s disappearing!” she vented to us. She also admitted she was tempted to splurge on a new car or a larger home just to “feel” successful, but deep down, she knew those wouldn’t bring lasting satisfaction. She was actually quite content with her car and her house prior to her income increase. Which is why she was the perfect candidate for a Mega Backdoor Roth.
What’s a Mega Backdoor Roth, Anyway?
A Mega Backdoor Roth is a strategy that lets high earners like Emily stow away extra money into a Roth account—far beyond the usual contribution limits—using a Solo 401(k). Unlike a traditional Roth IRA, which caps contributions at $7,000 in 2025 ($8,000 if you’re 50+), a Mega Backdoor Roth can let you save tens of thousands in tax-advantaged way. Also key, a Roth IRA has an income limit, and if you make over the limit, you can contribute less than the full amount, and eventually can’t contribute to it at all.
It’s called “mega” because there is another strategy called a “Backdoor Roth” which tries gets money into a Roth IRA even when a person’s income is above the limits (there are still lots of rules to follow), but the total contribution limit is still $7,000 per year for people younger than 50. The Mega Backdoor Roth, however, leverages the full 401(k) contribution limit, which is $69,000 in 2025 for employee and employer contributions (or $76,500 if you’re 50+).
Here’s how it works in a nutshell:
- Emily sets up a Solo 401(k), perfect for self-employed folks like her with no full-time employees.
- She maxes out her employee contribution ($23,000 in 2025). She’ll likely make these pre-tax to lower her taxable income.
- As her own “employer,” she contributes up to 25% of her net business income (up to a combined employee + employer limit of $69,000). Her CPA determined that if she made a $17,000 employer contribution (she’s allowed to do much more than that), she and her husband could get down to the 24% federal income tax bracket.
- What’s the backdoor Roth part? She makes a $29,000 after-tax contribution to the Solo 401(k) ($69,000 minus the $23,000 employee contribution and the $15,000 employer contribution), then converts that $29,000 to a Roth account for tax-free growth. She doesn’t get a current year tax deduction on that $29,000, but since she’s able to get down to the 24% federal income tax bracket by using the other contribution sources, current year tax deduction isn’t as necessary.
Why Emily Loves the Mega Backdoor Roth
Here’s why this strategy is so impactful for Emily:
- Tax-Free Growth
By converting after-tax contributions to a Roth, any growth that happens in Emily’s account will be tax-free, and she can withdraw it tax-free in retirement.
- Lowering Her Taxable Income
While the after-tax contributions don’t reduce her taxes now, her employer contributions (up to 25% of her income) and $23,000 of her employee contributions are pre-tax, shaving thousands off her taxable income each year.
- Flexibility for the Future
Roth accounts don’t have required minimum distributions (RMDs), so Emily can let her savings grow indefinitely or tap them early for big goals without penalties after age 59½.
- Sticking to Her Values
Instead of blowing her income on status symbols, Emily’s channeling it into financial future that will have a firm foundation for her and her family. She’d rather be able to retire earlier and enjoy some world travel with her husband than have more storage space at home that gets filled with belongings she wished she wouldn’t have purchased in the first place. Emily also plans to redirect the tax savings into college savings accounts for the kids.
How Emily Makes It Happen: A Step-by-Step Guide
Here’s how she’s setting up her Mega Backdoor Roth:
- Open a Solo 401(k): Emily chooses a provider that allows after-tax contributions and in-plan Roth conversions (not all do, so she checks carefully).
- Max Employee Contributions: She contributes $23,000 as the employee (pre-tax or Roth, and she chooses pre-tax).
- Add Employer Contributions: As her own boss, she contributes up to 25% of her net business income (also pre-tax or Roth, and she chooses pre-tax).
- Make After-Tax Contributions: She fills the gap to $69,000 with after-tax contributions. For example, if her employee + employer contributions total $40,000, she can add $29,000 after-tax.
- Convert to Roth: She immediately converts the after-tax contributions to a Roth account within the Solo 401(k), where they’ll grow tax-free.
- Rinse and Repeat: Emily does this annually, maximizing her tax-advantaged savings.
| Contribution Type | 2025 Limit | Tax Treatment | Emily’s Contribution |
| Employee Contribution | $23,000 | Pre-tax or Roth | $23,000 (pre-tax) |
| Employer Contribution | ~25% of income | Pre-tax | $17,000 (pre-tax) |
| After-Tax Contribution | Up to $69,000 | After-tax, converts to Roth | $29,000 (converts to Roth) |
| Total | $69,000 | $69,000 |
The Numbers: Emily’s Projected Savings
To show Emily the power of this strategy, we ran some projections. If Emily contributes $29,000 annually in after-tax contributions (converted to Roth) from age 38 to 65, assuming a 7% annual return, here’s what she could have:
| Age | Roth Balance (7% Return) |
| 45 | $297,000 |
| 55 | $986,000 |
| 65 | $2,340,000 |
That’s $2.34 million in tax-free money by retirement, just from the after-tax portion! Add in her employee and employer contributions, and Emily’s looking at a retirement nest egg that could make her CPA weep with joy.
The Catch: Cons and Considerations
No strategy is perfect, and Emily needs to weigh the downsides:
- Upfront Tax Hit: After-tax contributions don’t reduce her taxable income now, so she’s still paying taxes on that $29,000. This stings, but the tax-free growth is worth it long-term. And through collaboration with Emily’s CPA, we were able to get her and her husband’s income below the 32% bracket in to the 24% bracket, which is much more palatable.
- Plan Complexity: Not all Solo 401(k) providers allow after-tax contributions or in-plan conversions. We have access to straightforward, relatively low-complexity options, though, and what complexity remains mostly falls on us and the CPA.
- Income Limits: If Emily’s business grows and she hires full-time employees, she might lose eligibility for a Solo 401(k).
- Paperwork: Converting after-tax contributions to Roth requires some record-keeping to avoid IRS headaches. Again, though, that mostly falls on us and the CPA.
Emily’s Verdict: Worth the Effort?
After weighing the pros and cons, Emily agreed it made sense for her. The Mega Backdoor Roth lets her save way more than a traditional IRA or Roth IRA – or even other options like a SIMPLE IRA or SEP IRA, and comes with some great tax benefits.
Ready to Be Like Emily?
Now to be clear, and if you hadn’t already guessed, Emily isn’t a real client. But this story is based on many of our clients who are in very similar situations. The problems and opportunities she faced, along with the solutions we proposed, are the types of problems, opportunities and solutions that we help many of our clients with. If you’re a high-earning solopreneur like Emily, the Mega Backdoor Roth could be your ticket to a tax-advantaged retirement. It’s not a one-size-fits-all, but for those in high tax brackets who want to save aggressively without lifestyle creep, it’s hard to beat. If you want to explore what it would look like to work with us, reach out. And who knows? You might just end up with a retirement fund that makes Emily jealous.
Disclaimer: Case studies are hypothetical and do not relate to an actual client of Flagstone Financial Management, a registered investment adviser with the Securities and Exchange Commission. Clients or potential clients should not interpret any part of the content as a guarantee of achieving similar results or satisfaction if they engage Flagstone Financial Management for investment advisory services.
The information is for general and educational purposes only and is not intended as tax or accounting advice. Information provided should not be solely relied upon for decision making. Please consult your tax, or accounting professional regarding your specific situation. Investments involve risk and have the potential for complete loss. It should not be assumed that any recommendations made will necessarily be profitable.
