Law Firm Retirement Plans for Multi-Partner Firms: 401(k), Cross-Tested Plans, and Cash Balance Stacking

Law firms with multiple equity partners and staff sit in a unique position for retirement plan design. The partners earn high incomes, the firm is classified as a specified service trade or business (SSTB) under IRC 199A(d)(2) (which means no qualified business income deduction above the income threshold), and the only reliable lever left for reducing taxable income is putting money into a qualified retirement plan. A solo practitioner’s playbook does not translate to a multi-partner firm with employees: a solo 401(k) is off the table, nondiscrimination testing becomes a constraint, and the plan must cover associates and staff at real cost. The payoff, though, is substantial. A properly designed combination of a 401(k) with profit sharing, a cross-tested allocation formula, and a cash balance defined benefit plan can allow each equity partner to defer $200,000 to $350,000 or more per year, while staff receives meaningful but far less expensive benefits that satisfy testing requirements.

Why are law firms ideal for aggressive retirement plans?

Three characteristics make law firms the best-case scenario for retirement plan optimization. First, partner incomes are high, commonly $400,000 to $1,000,000 or more, taxed at 37% federal plus state income tax plus the 0.9% additional Medicare tax. Second, law firms are SSTBs. Under IRC 199A, partners with taxable income above $394,600 (MFJ) or $197,300 (single) in 2025 get zero QBI deduction. A manufacturer earning the same income deducts 20% of QBI. A lawyer cannot. This makes every dollar deferred into a retirement plan proportionally more valuable.

Third, the ratio of owners to employees tends to be favorable. The nondiscrimination rules do not require equal contributions. They require that benefits, as a percentage of compensation, satisfy certain statistical tests. Cross-tested plan design exploits the age-weighted nature of these tests to skew contributions heavily toward older, higher-paid partners while satisfying the rules through safe harbor contributions and cross-tested allocations.

What are the 2025 401(k) and profit-sharing limits?

The 401(k) component of a multi-partner firm’s retirement plan has two pieces: the employee deferral (what each participant elects to contribute from their own compensation) and the employer profit-sharing contribution (what the firm contributes on behalf of each participant).

2025 employee deferral limits:

• Standard deferral: $23,500
• Age 50+ catch-up contribution: additional $7,500 (total deferral: $31,000)
• Age 60 to 63 super catch-up (SECURE 2.0, Section 109): additional $11,250 instead of $7,500 (total deferral: $34,750)

2025 combined limit under IRC 415(c):

• Employee deferral + employer profit-sharing contribution: $70,000
• With age 50+ catch-up: $77,500
• With age 60 to 63 super catch-up: $81,250

The employer profit-sharing contribution is funded by the firm and allocated to each participant’s account. In a traditional profit-sharing plan, the allocation is pro rata (each participant receives the same percentage of compensation). In a cross-tested plan, the allocation is not pro rata, and this is where the design gets interesting for law firms.

Safe harbor 401(k). Most multi-partner law firms adopt a safe harbor design to avoid the ADP/ACP nondiscrimination tests on deferrals. The safe harbor requires either a 3% nonelective contribution to all eligible employees or a 4% matching contribution. The 3% nonelective is the more common choice: for a staff member earning $60,000, the cost is $1,800 per year. For ten staff members, $18,000 total. That is a modest price for allowing partners to maximize their own deferrals without testing constraints.

How do cross-tested plans favor partner contributions?

A cross-tested plan (also called a new comparability plan) is a defined contribution profit-sharing plan that divides participants into groups and allocates different contribution rates to each group. The plan passes nondiscrimination testing not by giving everyone the same dollar amount or the same percentage of pay, but by demonstrating that the projected retirement benefits (expressed as an equivalent benefit accrual rate) satisfy the general nondiscrimination test under IRC 401(a)(4).

The mechanics work like this. The plan defines two or more groups, typically “equity partners” and “all other employees.” The equity partners receive a high profit-sharing allocation (say, 20% to 25% of compensation). The staff receives a lower allocation (typically the 3% safe harbor contribution plus a small additional amount, often 5% to 7.5% total). The plan then “cross-tests” these allocations by converting each participant’s dollar contribution into an equivalent defined benefit accrual rate, which accounts for the participant’s age (younger participants have more years for the money to grow, so a smaller contribution today produces a larger projected benefit). Because the partners are typically older than the associates and staff, a dollar contributed for a 55-year-old partner produces a smaller projected benefit than a dollar contributed for a 28-year-old associate. This means the partners can receive a much larger dollar contribution while the projected benefit accrual rates remain comparable.

The result: in a firm where the three equity partners are ages 50, 55, and 60, and the associates and staff are ages 25 to 40, the partners might each receive $45,000 to $50,000 in profit-sharing contributions (plus their own $23,500 to $34,750 deferral), while each staff member receives $3,000 to $5,000. The total staff cost might be $50,000 to $75,000 for 15 employees, while the three partners collectively defer over $200,000 in profit sharing alone.

When cross-testing fails. The math does not always work. If the partners are young (under 45) or the staff is old (over 50), the age-weighted advantage disappears or reverses. If the firm has a large number of highly compensated employees (senior associates earning over $155,000 in 2025), those employees may need to be grouped with the partners, which increases the cost. The plan’s actuary or TPA (third-party administrator) runs the nondiscrimination testing annually, and the contribution rates may need to be adjusted each year based on the actual participant census.

How does a cash balance plan work for a multi-partner firm?

A cash balance plan is a defined benefit plan under IRC 401(a), but it looks like a defined contribution plan to the participants. Each participant has a hypothetical account that receives annual “pay credits” (employer contributions) and “interest credits” (a guaranteed rate of return, typically 4% to 6%). The employer’s actual contribution is the amount determined by the plan’s actuary to be necessary to fund the promised benefits, and this amount is deductible under IRC 404.

The contribution limits for a cash balance plan are based on the maximum annual benefit at retirement age, which is $280,000 for 2025 under IRC 415(b). The annual contribution required to fund that benefit depends on the participant’s age (how many years remain until retirement) and the plan’s interest crediting rate. Older participants need larger annual contributions because the money has fewer years to grow.

Approximate annual cash balance plan contributions by age (2025):

• Age 40: $80,000 to $110,000
• Age 45: $110,000 to $150,000
• Age 50: $150,000 to $200,000
• Age 55: $200,000 to $280,000
• Age 60: $280,000 to $350,000+

These ranges are approximate because the actual contribution depends on the plan’s interest crediting rate, the participant’s compensation history, and actuarial assumptions. The critical difference from a solo practitioner’s cash balance plan is that a multi-partner firm’s plan must also cover eligible employees. However, the cash balance plan can be designed with different benefit formulas for different groups (partners and staff), and the staff benefit formula is typically much lower (3% to 5% of compensation as the annual pay credit, compared to $150,000+ for each partner).

The employee cost. For a staff member earning $60,000 with a 5% pay credit, the annual cash balance contribution is $3,000. For 15 staff members, the total is $45,000. The partners, meanwhile, are each contributing $150,000 to $280,000. The ratio of partner benefit to employee cost is highly favorable, and the tax savings from the partner contributions far exceed the employee cost.

Why does the SSTB tag make retirement plans more valuable?

Under IRC 199A, pass-through business owners can deduct up to 20% of qualified business income. Law firms are SSTBs, and the deduction phases out entirely above $197,300 (single) or $394,600 (MFJ) in 2025. Most equity partners are well above these thresholds. A construction company owner earning $600,000 gets a $120,000 QBI deduction. A law firm partner earning $600,000 gets nothing.

Every dollar of retirement plan contribution therefore delivers more value to a law firm partner than to a comparably situated non-SSTB owner. A $280,000 cash balance contribution for a 60-year-old partner at a 37% federal rate plus state tax plus the 0.9% additional Medicare tax can save over $110,000 in a single year. For law firm partners, the retirement plan is the deduction.

What did SECURE 2.0 change for law firms?

SECURE 2.0 (enacted in December 2022) introduced several provisions that affect retirement plan design for law firms, with the most significant ones taking effect in 2025 and 2026.

Super catch-up for ages 60 to 63 (effective 2025). Participants who are ages 60, 61, 62, or 63 during the calendar year can make catch-up contributions of $11,250 (the greater of $10,000 or 150% of the standard $7,500 catch-up), instead of the standard $7,500 for those age 50 and older. For a 62-year-old equity partner, this increases the maximum 401(k) deferral from $31,000 to $34,750. The provision is optional for plan sponsors, but there is no reason for a law firm not to adopt it, given that the additional deferral benefits the partners and costs the firm nothing.

Roth employer contributions (effective 2023, practical adoption still limited). Employers can now designate matching and profit-sharing contributions as Roth (after-tax) at the participant’s election. For a partner who expects to be in a high tax bracket in retirement (not uncommon for attorneys who continue consulting, serving on boards, or earning investment income), Roth employer contributions provide tax-free growth and withdrawals. The trade-off is that the Roth contribution does not reduce current taxable income.

Mandatory Roth catch-up for high earners (effective 2026). Starting in 2026, participants who earned more than $145,000 in FICA wages in the prior year must make catch-up contributions on a Roth (after-tax) basis. For law firm partners earning well above this threshold, all catch-up contributions will be Roth. Plans that do not offer a Roth option will not be able to accept catch-up contributions from these participants at all. Multi-partner firms should amend their plans to include a Roth option before the 2026 deadline to preserve the catch-up benefit.

Automatic enrollment (effective for new plans established after December 29, 2022). New 401(k) plans must automatically enroll eligible employees at a deferral rate of at least 3% (increasing by 1% annually up to at least 10%). Existing plans are grandfathered.

What other plan design tools manage the employee cost?

Beyond the safe harbor and cross-testing covered above, three design features help. First, an integrated (permitted disparity) design under IRC 401(l) applies a higher contribution rate on compensation above the Social Security taxable wage base ($176,100 in 2025), directing more of the employer contribution to the partners. Second, eligibility exclusions: plans can require 1,000 hours of service, excluding part-time staff (though SECURE 2.0 requires long-term part-time employees with 500+ hours in three consecutive years to become eligible for deferrals starting in 2025). Third, vesting schedules of up to six years (graded) or three years (cliff) allow forfeitures from departing associates to reduce future employer contributions.

Is a SEP-IRA a viable alternative?

For a solo practitioner or a very small firm (one or two partners, no staff), a SEP-IRA is simpler to administer than a 401(k). The maximum contribution is 25% of compensation (effectively about 20% of net self-employment income for partners), up to $70,000 in 2025. There are no employee deferrals, no nondiscrimination testing, no annual Form 5500 filing for plans with assets under $250,000, and no TPA fees.

The drawback for multi-partner firms is that a SEP-IRA requires the same contribution percentage for all eligible employees. If the firm contributes the effective 20% of net SE income for the partners, it must contribute 25% of pay for every eligible employee. For a firm with ten associates earning $150,000, that is $375,000 per year in mandatory employee contributions. There is no cross-testing, no age-weighting, and no ability to differentiate between partners and staff. The added complexity and cost of a 401(k) with cross-tested profit sharing pays for itself through the differential contribution rates.

If you are a solo practitioner or a firm with no employees, the solo practitioner retirement plan guide covers the solo 401(k) and cash balance plan design in detail.

How does entity structure affect contribution calculations?

The firm’s entity structure determines how each partner’s compensation is defined for retirement plan purposes, which directly affects the maximum contribution.

Partnership or LLC taxed as a partnership. Partners are not “employees” of the partnership. Their compensation for retirement plan purposes is net self-employment income: the partner’s distributive share of partnership income, reduced by one-half of self-employment tax and by the partner’s own employer contribution. The calculation is circular (the contribution reduces the income base it’s figured on), but it resolves through the IRS worksheets in Publication 560. The effective employer contribution rate is 20% of net earnings after the self-employment tax adjustment (not 25%, because the contribution itself comes out of the base). Guaranteed payments under IRC 707(c) are included in net self-employment income for this calculation.

S corporation. Partners who are shareholders of an S corporation law firm receive W-2 wages (reasonable compensation) and distributions. Retirement plan contributions are calculated based on W-2 wages only, not distributions. The employer contribution is up to 25% of W-2 compensation. This means that the “reasonable compensation” determination directly affects the maximum retirement plan contribution. A partner who sets W-2 wages too low (to minimize FICA) also limits retirement plan contributions. Firms using an S-corp structure must balance the FICA savings against the lost retirement plan contribution capacity. For high-income partners, the retirement plan math often favors higher W-2 wages (and thus higher FICA) because the tax deferral from additional retirement plan contributions exceeds the FICA cost.

C corporation. C-corp law firms (uncommon) make deductible employer contributions based on W-2 compensation, subject to the IRC 415(c) limit ($70,000) and the IRC 414(s) compensation limit ($350,000 for 2025).

What should I do next?

If your firm has equity partners deferring less than $70,000 per year, the plan is underperforming. If the firm has no cash balance plan and the partners are over 45, the gap between what you are deferring and what you could be deferring is likely six figures per partner per year. If the current plan is a SEP-IRA and the firm has employees, a conversion to a 401(k) with cross-tested profit sharing will almost certainly produce a better result for the partners.

• Solo practitioner retirement plans, the solo 401(k) and cash balance plan design for firms with no employees
• Law firm partner compensation and guaranteed payments, how guaranteed payments, distributive shares, and SE tax interact with retirement plan contributions
• Law firm entity structure, how the choice of entity (LLC, LLP, PC, S-corp) affects both tax treatment and retirement plan contribution calculations
• Law firm bookkeeping, chart of accounts setup including partner capital accounts, draws, and the bookkeeping for employer retirement plan contributions
• Law firm associate and partner-track compensation, how associate compensation structures affect nondiscrimination testing and plan design
• Law firm merger and acquisition tax implications, how plan assets and liabilities are handled when firms merge or a partner moves to a new firm

Related guides:

• Tax Planning for IT Consulting Firms and Managed Service Providers: SSTB Classification, R&D Credits, and Entity Structure

This guide is general information, not tax advice for your specific situation. Which points apply, and how, depends on your facts.