You may have heard that when you contribute to a cash balance plan along with a 401(k) profit-sharing plan, your profit-sharing contributions are “capped at 6%.” Why is this the case?
Most people set up cash balance plans and other defined benefit structures to maximize retirement contributions. As such, they are not pleased to hear about this limitation.
How does this rule work and why is it in place? In this post, we will discuss the issue and also show you the specific reference to the IRS tax code. Let’s dive in!
Background
Technically speaking, you don’t have to comply with “6% rule.” But if you don’t you will have to have a PBGC covered plan or follow the “31% rule.”
PBGC covered plans are not for solo plans, nor are they for professional services companies. The 31% rule will, in the vast majority of situations, reduce overall contributions. So, we won’t spend much time discussing these options. In reality, you are likely stuck having to stick with the 6% rule.
In summary, if you want to get around the 6% rule, you will have to live with one of the following rules:
- The 31% rule;
- Have a PBGC covered plan; or
- Not be able to take a deduction for amounts contributed over 6% (more about this shortly).
Understanding the 401(k) Components
A 401(k) arrangement can include multiple contribution types. There are generally two types of contributions:
- Employee elective deferrals; and
- Profit-sharing.
Employer money includes matching and profit-sharing contributions, and those are the focus of the 6% discussion. The “6% cap” is about employer contributions, not employee deferrals.
Elective deferrals are typically not counted in that employer threshold, because they are employee contributions. That is why someone can often max deferrals while still targeting 6% on the employer side.
401(k) profit-sharing plans normally have a cap of 25% of compensation. Defined benefit deductions work differently and are tied to actuarial funding calculations and liabilities.
When one business is funding both plans, the IRS tax code applies combined deduction limits. That combined framework is where Section 404(a)(7) becomes important.
IRC Section 404(a)(7) is a deduction rule, not a contribution ceiling
A cash balance plan is type of defined benefit plan, while a 401(k) profit-sharing plan is a type of defined contribution plan. These are important distinctions under the IRS tax code.
The main driver is IRC Section 404(a)(7), which can limit deductions when a defined benefit plan and a defined contribution plan overlap. So, the issue is often tax deductibility, not whether the 401(k) plan document permits a higher allocation.
Section 404 controls how much the employer can deduct for retirement plan contributions in a year. A plan can allow a contribution while the tax rules limit the current-year deduction. That mismatch can create compliance headaches and potential excise tax exposure in some situations. Because of that risk, advisors generally design to what is clearly deductible.
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Section 404(a)(7) adds another layer when both plan types exist together. If a defined benefit plan and a defined contribution plan have overlapping coverage and employer allocations, a combined deduction limit can apply.
The goal is to prevent employers from stacking a very large defined benefit deduction and a very large defined contribution deduction in the same year. This combined approach tends to matter most in owner-heavy, PBGC-exempt cash balance arrangements.
You can find the above IRS code here.
Where the 6% number actually comes from
The 6% concept comes from a threshold built into Section 404(a)(7). If employer contributions to the defined contribution plan do not exceed 6% of aggregate compensation for the relevant defined contribution beneficiary group, the combined limitation generally stays dormant.
When employer defined contribution contributions stay at or below 6%, the deduction analysis usually remains simpler. The cash balance deduction can often be handled under its normal defined benefit deduction rules.
The defined contribution employer amount is handled under the normal defined contribution deduction framework. This is the practical reason 6% is such a common design target.
Once employer defined contribution contributions exceed 6%, only the excess above 6% is pulled into the combined deduction limitation calculation. In plain language, the extra profit-sharing starts competing with the cash balance plan’s deduction capacity.
Is a Cash Balance or Defined Benefit Plan Right For You?
That can reduce how much is deductible in the current year, or force a redesign if the employer wants to avoid nondeductible contributions. So, the “cap” is really a point where added profit-sharing becomes more complicated and potentially less efficient.
Here is a simple table summarizing the common planning framework:
| Scenario | What happens | Why it matters | Common design response |
|---|---|---|---|
| No overlapping beneficiaries | Combined deduction limit may not apply | Deductions are evaluated separately | Structure eligibility and allocations carefully |
| Overlap, employer DC ≤ 6% | Combined limit usually stays dormant | DB deduction is less likely to be crowded out | Keep profit-sharing near 6% |
| Overlap, employer DC > 6% | Excess over 6% is tested under combined rules | Excess can reduce deductible room | Model the combined limit or redesign contributions |
Why Congress structured the rule this way
Congress generally wants employers to be able to deduct retirement plan contributions. At the same time, Congress does not want unlimited current-year tax sheltering through stacked deductions. Without a combined limitation, an employer could potentially claim a very large cash balance deduction and also a very large profit-sharing deduction. Section 404(a)(7) operates as a guardrail against that outcome.
The 6% threshold is also intended to avoid punishing typical, employee-friendly plan designs. A modest employer contribution in a defined contribution plan is common in the market. So the statute effectively gives employers room to provide a baseline employer contribution without triggering heavy combined-limit calculations. When the employer defined contribution amount becomes larger, the Code requires more rigorous combined testing.
Many small cash balance plans are PBGC-exempt, and those plans often produce the biggest deductions. That context helps explain why the combined limitation becomes a practical issue for professional practices. The rule is trying to preserve a balance between retirement savings incentives and reasonable deduction boundaries. The result is a widely used design norm: max deferrals, about 6% employer defined contribution, and the desired cash balance funding.
Sole proprietors and the “deemed wage” problem
For a sole proprietor, the compensation base is not a W-2 wage. Instead, it is earned income derived from net earnings from self-employment after required adjustments.
One adjustment is the deduction for one-half of self-employment tax. Another key feature is that earned income is reduced by deductible retirement plan contributions, which creates circular math.
That circularity is why people use the phrase “deemed wage.” It is a practical way to describe the net compensation base used for contribution calculations after adjustments.
If the deemed wage is lower than expected, the 6% employer contribution amount is lower too. This surprises owners who plan using gross business profit rather than earned income.
Elective deferrals are generally treated differently from employer contributions in this framework. They are not the same thing as employer profit-sharing for the 6% threshold concept.
So a sole proprietor may still maximize deferrals while keeping employer profit-sharing at roughly 6% of earned income. But the earned income calculation should be done early to avoid designing around the wrong base.
Practical design moves and common pitfalls
Most owner-heavy cash balance designs aim for predictable deductions with minimal cleanup. A common approach is maximum elective deferrals, an employer defined contribution amount around 6%, and then the cash balance contribution sized to reach the tax deduction goal.
This approach often avoids dragging additional defined contribution dollars into the combined deduction limitation. It also makes year-end planning easier.
One common pitfall is forgetting that matches and safe harbor nonelective contributions are employer contributions. If you promise a match and then add 6% profit-sharing, you can exceed the threshold unintentionally.
Another pitfall is changing eligibility or allocation rules and accidentally creating more overlap between plans. When overlap changes, the combined-limit analysis can change as well.
Another practical issue is coordination among the actuary, TPA, and tax preparer. Cash balance funding can be large, and profit-sharing decisions can affect deductibility if you push beyond 6%.
Modeling should happen before the employer commits to a contribution strategy. That is why annual funding projections and deduction forecasting are so valuable.
Key Takeaways
The 6% “cap” is best understood as a deduction planning threshold tied to IRC Section 404(a)(7). It is not a universal limit on what a plan can allocate, and it is not a cap on employee elective deferrals.
Staying at or below 6% in employer defined contribution allocations often keeps combined deduction limitations quieter. Going above 6% can pull the excess into combined-limit calculations and reduce deduction flexibility.
Cash balance plans are designed to create large deductible contributions, and that is often the primary objective. Because the defined benefit deduction can be large, additional employer profit-sharing above 6% can become less efficient or more complex.
For sole proprietors, the 6% base is earned income, not W-2 wages, which can reduce the “deemed wage” and create circular math. The cleanest default design for many owners remains maximum deferrals, about 6% employer defined contribution, and a tailored cash balance contribution sized to the deduction target.
