The Ultimate Retirement Hack

_{The Ultimate Retirement Hack}

How High Earners With a Side Business Can Stack Two 401(k)s

I was talking with a friend the other day who is a pilot for a large airline and also runs a side business. The conversation had me thinking about his retirement plan options — specifically his 401(k).

Here’s the question I started thinking about: with a solid W-2 income from the airline and meaningful revenue coming in from his business, how much could he actually put into retirement accounts in a single year?

If your first instinct was “$72,000 — because that’s the IRS max,” you’d be in good company. You’d also be wrong. You could be leaving tens of thousands of dollars in tax-advantaged savings on the table every year.

The secret comes down to a rule that most people — and even a lot of accountants — don’t fully appreciate: the IRS limit isn’t per person. It’s per employer. And a side business is a completely separate employer.

First, Let’s Bust a Very Common Myth

Almost everyone assumes the IRS has one big retirement contribution ceiling per person. It’s an understandable assumption. But the rules are a bit more nuanced — and in this case, that nuance is worth a significant amount of money.

The IRS actually operates with two separate limits that work very differently from each other:

That second row is where the real opportunity lives. Because a side business is a separate employer, it gets its own $72,000 ceiling — completely independent of any corporate 401(k).

The Solo 401(k): The Side Business Owner’s Secret Weapon

When you own a business — whether you’re a freelancer, consultant, LLC owner, or running any kind of self-employed operation — you can open what’s called a Solo 401(k), sometimes referred to as an Individual 401(k) or Self-Employed 401(k).

The Solo 401(k) allows you to contribute in two separate capacities:

• As the employee of your own business, where the standard $24,500 limit applies
• As the employer of your own business, which is a separate contribution of up to roughly 25% of your net self-employment income

Here’s where it gets interesting: if you’ve already maxed out your employee contribution at a corporate job, you skip the employee side of the Solo 401(k) entirely and go straight to the employer contribution. You’re not double-dipping on any limit. You’re using a completely separate, IRS-sanctioned bucket.

Running the Numbers: A Real-World Example (2026 Limits)

Let’s put actual numbers to this. Take someone earning $300,000 in W-2 income from a corporate job and another $200,000 from a side business. Here’s what their retirement picture could look like:

Bucket No. 1 — Corporate 401(k)

Bucket No. 2 — Solo 401(k) for the Side Business

Nearly $89,000 per year flowing into retirement accounts. Pre-tax. That figure is not an error.

The Fine Print (Because There Is Always Some)

A few important details worth knowing before you call your advisor with the good news:

• The Solo 401(k) employer contribution calculation is not exactly 25%. It works out to roughly 20% of net self-employment income after accounting for the self-employment tax deduction. On $200,000 of SE income, the realistic range is $37,000 to $46,500. A CPA should calculate the precise number.
• Catch-up contributions make this strategy even more powerful. If you are 50 or older in 2026, you can add another $8,000 as an employee catch-up contribution. Those ages 60 through 63 can contribute $11,250 under the newer “super catch-up” provision introduced by SECURE 2.0.
• New for 2026 — the high-earner Roth catch-up rule: If you earned more than $150,000 in 2025, any catch-up contributions must now be made as Roth (after-tax) contributions. This is a SECURE 2.0 requirement that went into effect this year.
• The Solo 401(k) plan must be established before December 31st of the tax year you intend to use it. You can fund it up to your tax filing deadline, but the plan itself has to exist before year-end.
• Work with a CPA who understands self-employed retirement plans. This strategy is absolutely worth pursuing, but the calculations and setup details matter. This is not a do-it-yourself situation.

The Bottom Line

If you have a W-2 job and self-employment income — whether you’re a pilot with a side business, a consultant moonlighting after hours, or anyone in between — you may be sitting on one of the most underutilized tax advantages in the U.S. tax code.

The ability to stack a corporate 401(k) with a Solo 401(k) can put close to $89,000 per year into tax-advantaged retirement accounts. Most people with side income never pursue this because they assume the $72,000 limit is per person and stop there.

Now you know better. The next step is making sure your advisor does too.

This article is for educational purposes only and does not constitute tax, legal, or investment advice. Please consult a qualified professional for guidance specific to your situation.