A Solo 401(k)—also known as a one-participant 401(k)—is one of the most powerful retirement plans available to self-employed business owners. It offers high contribution limits, flexible investment options, and simplified administration.
But what happens when your business grows and you hire employees?
Growth is a great problem to have—but hiring employees can change your retirement plan obligations. In this article, we’ll break down exactly what happens, when action is required, and what your options are if your Solo 401(k) no longer qualifies.
Watch: Learn what happens to your solo 401k once you hire a W-2 employee
What Is a Solo 401(k)?
A Solo 401(k) is designed specifically for:
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Self-employed business owners
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Businesses with no full-time W-2 employees
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Owners and their spouses (who may participate)
Multiple owners can participate in the same Solo 401(k), and spouses working in the business may also participate.
The reason the Solo 401(k) is so streamlined is that it is exempt from many complex ERISA testing rules—because it only covers owners and spouses.
However, once non-owner employees become eligible, the plan is no longer considered a “one-participant” plan.
Why Hiring Employees Changes Everything
When your business hires common-law W-2 employees, you must evaluate whether those employees become eligible to participate in a retirement plan.
There are two key eligibility rules to understand:
The Full-Time Employee Rule (Traditional Rule)
Under long-standing IRS rules:
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An employee becomes eligible if they work 1,000 hours or more in a 12-month period
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Applies to W-2 employees
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Independent contractors (1099) can always be excluded
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Employees under age 21 can also be excluded
Example
If an employee works 1,000 hours during their first 12 months of employment and meets the age requirement, your Solo 401(k) must:
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Be converted (restated) into a traditional 401(k), or
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Be terminated and rolled over to another retirement structure
You can no longer maintain it as a Solo 401(k).
The Long-Term Part-Time (LTPT) Rule
The SECURE Act 1.0 introduced the long-term part-time employee rule.
The SECURE Act 2.0 expanded and modified it.
Current Rule (Beginning 2025)
Employees must be allowed to participate if they:
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Work 500 or more hours per year
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For 2 consecutive years
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And are age 21 or older
Originally, the rule required three years—but SECURE 2.0 reduced it to two years starting in 2025.
Important Clarification
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1,000 hours in one year → immediate eligibility after service period
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500–999 hours → must meet threshold for two consecutive years
If the employee works under 500 hours in the second year, the clock resets.
When Must You Comply?
If an employee meets eligibility requirements:
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You must allow them to participate by the next plan entry date
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Common entry dates are January 1 or July 1
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Failing to comply may create IRS qualification issues
At that point, you cannot continue operating under a Solo 401(k) structure.
What Are Your Options?
If your Solo 401(k) no longer qualifies, you have three primary non-taxable options:
Option 1: Restate to a Traditional 401(k)
You can convert (restate) your Solo 401(k) into a full traditional 401(k) plan.
This allows you to:
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Add employee eligibility provisions
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Potentially implement safe harbor or matching contributions
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Maintain your retirement structure
Tax impact? None.
Your assets remain inside a qualified retirement plan.
This is often the best solution for growing businesses.
Option 2: Terminate the Solo 401(k) and Roll to an IRA
You may:
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Roll pre-tax funds to a Traditional IRA
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Roll Roth Solo 401(k) funds to a Roth IRA
As long as the rollover is done as a direct rollover, there is no tax impact.
This option maintains tax-deferred or Roth status.
Option 3: Roll to a New Employer’s 401(k)
If you close your business and become a W-2 employee elsewhere:
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You may roll your Solo 401(k) into your new employer’s 401(k)
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Most employer plans accept incoming rollovers
Tax impact? None, if done properly as a direct rollover .
What You Should Avoid
Taking a distribution from your Solo 401(k) is generally a last resort.
Unless rolled over within 60 days, a distribution may trigger:
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Income taxes
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Early withdrawal penalties (if under age 59½)
The purpose of a 401(k) is long-term retirement growth—not short-term liquidation.
Can You Strategically Manage Employee Hours?
Some business owners:
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Keep employees under 1,000 hours
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Monitor 500-hour thresholds carefully
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Track payroll precisely to avoid triggering eligibility
While this can work short-term, it requires careful compliance monitoring.
For growing businesses, converting to a traditional 401(k) is often the cleaner long-term solution.
Strategic Planning Tip
Before hiring:
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Project expected employee hours
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Evaluate business growth trajectory
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Compare administrative costs of a Solo 401(k) vs. traditional 401(k)
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Consult your plan provider proactively
Being proactive today prevents costly compliance corrections tomorrow.
Final Takeaway
Hiring employees is a milestone—but it changes your retirement plan obligations.
If a W-2 employee:
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Works 1,000 hours in 12 months, or
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Works 500+ hours for two consecutive years
Your Solo 401(k) must either:
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Be restated to a traditional 401(k)
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Be rolled to an IRA
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Be rolled into a new employer’s 401(k)
Understanding these rules helps you:
✔ Stay compliant
✔ Avoid IRS penalties
✔ Protect your tax-advantaged retirement savings
✔ Plan strategically as your business grows
If you’re unsure how hiring affects your Solo 401(k), consult with your plan provider before making staffing decisions. Proper planning ensures your retirement strategy evolves with your business success.
