Retirement Plans for Construction Business Owners: Solo 401(k), SEP-IRA, Cash Balance, and Safe Harbor Options

Construction business owners tend to have two traits that make retirement planning both urgent and complicated: high income in good years and unpredictable income from one year to the next. A GC who clears $400,000 in a year with three large commercial projects might drop to $180,000 the following year when the pipeline thins out. The right retirement plan lets the owner shelter a significant portion of income from taxes in a strong year without creating a mandatory funding obligation that becomes a cash-flow problem in a lean one. The wrong plan, or no plan at all, means paying top marginal rates on income that could have been deferred for decades.

Which plan works best for a solo contractor?

If the business has no common-law employees other than the owner (and possibly a spouse), three plans are in play: the SEP-IRA, the solo 401(k), and the SIMPLE IRA. Each has different contribution mechanics, and for most construction owners earning above $100,000, the solo 401(k) wins.

The SEP-IRA is the simplest to set up: no plan document filed with the IRS, no annual Form 5500 filing until the plan assets exceed $250,000, and contributions are made entirely by the employer (there is no employee deferral component). The contribution limit is 25% of W-2 compensation for S-Corp owners, or approximately 20% of net self-employment income for sole proprietors and single-member LLCs (the reduction accounts for the self-employment tax deduction). The maximum is $70,000 for 2025. The SEP works well for owners who want a hands-off plan with no administrative overhead, but it has a structural disadvantage: no employee deferral means no catch-up contributions for owners age 50+, and the contribution is a straight percentage of compensation with no way to front-load the deferral. SECURE 2.0 introduced a Roth option for SEP-IRAs starting in 2023, but implementation by custodians has been slow.

The solo 401(k) offers the same 25% employer profit-sharing contribution as the SEP, plus an employee deferral of $23,500 for 2025 ($31,000 if age 50+, $34,750 if age 60-63 under the SECURE 2.0 super catch-up provision). The combined maximum is $70,000, or $77,500 for 50+, or $81,250 for 60-63. The employee deferral component is the key advantage: a 45-year-old S-Corp owner paying themselves a $100,000 salary can defer $23,500 as an employee deferral plus $25,000 as a 25% employer profit-sharing contribution, for a total of $48,500. The same owner with a SEP-IRA would be limited to $25,000 (25% of the $100,000 salary). The solo 401(k) also allows Roth deferrals, plan loans (up to $50,000 or 50% of the vested balance), and catch-up contributions that the SEP does not.

The SIMPLE IRA is designed for small businesses and has lower limits: $16,500 employee deferral for 2025, plus a $3,500 catch-up for age 50+. The employer makes either a dollar-for-dollar match up to 3% of compensation or a flat 2% non-elective contribution. The total contribution capacity is well below the solo 401(k) or SEP, so the SIMPLE IRA only makes sense for owners with modest income who want the lowest possible administrative cost, or for businesses that will eventually add employees and want a plan with a built-in matching structure. For a construction owner earning $200,000+, the SIMPLE IRA leaves too much tax deferral on the table.

How does an S-Corp affect retirement contributions?

Most construction companies above $80,000-$100,000 in net income operate as S-Corps (or LLCs taxed as S-Corps) to save on self-employment tax. The S-Corp structure requires the owner to take a “reasonable salary” as W-2 wages, and the remaining profit passes through as a distribution that is not subject to Social Security and Medicare tax. This creates a direct interaction with retirement plan contributions, because the employer contribution percentage (25% for a 401(k) profit-sharing or SEP-IRA) is calculated on the W-2 salary, not on total business income.

Setting the salary too low reduces the retirement plan contribution capacity. A construction company owner with $300,000 in net business income who pays themselves a $60,000 salary (which the IRS would likely challenge as unreasonably low for a GC) can only contribute $15,000 as the employer profit-sharing portion (25% of $60,000), plus the $23,500 employee deferral, for a total of $38,500. If the same owner sets a reasonable salary of $120,000, the employer contribution rises to $30,000, and the total reaches $53,500. At $150,000 in salary, the employer contribution is $37,500, and the total is $61,000.

The tension is real: higher salary means higher FICA taxes (the 2025 Social Security wage base is $176,100, so salaries above that escape the 6.2% employee share on the excess but still pay the 1.45% Medicare tax and the 0.9% additional Medicare tax above $200,000). The optimal salary balances FICA savings against retirement plan contribution capacity. For most construction S-Corp owners, the salary should be high enough to maximize the desired retirement contribution without paying unnecessary FICA on excess dollars. This is a calculation, not a guess, and it changes every year based on income, age, and the chosen plan type. Worker classification issues (covered in detail in our guide to construction worker classification) can also affect the reasonable salary analysis if the IRS reclassifies 1099 subs as employees.

What if my construction company has field employees?

The moment a construction company has common-law employees (laborers, carpenters, equipment operators, foremen), the solo 401(k) is no longer available, the SEP-IRA becomes expensive, and plan design gets more complicated. The core issue is nondiscrimination: IRC 401(a)(4) requires that retirement plan benefits do not discriminate in favor of highly compensated employees (HCEs), which in most construction companies means the owners and key field superintendents.

A SEP-IRA with employees requires the employer to contribute the same percentage for every eligible employee as it contributes for the owner. If the owner gets a 25% contribution, every eligible employee gets 25% of their compensation too. For a company with ten field workers averaging $55,000 in wages, a 25% SEP contribution means $137,500 in additional employer contributions for the crew, on top of the owner’s contribution. Most construction owners abandon the SEP when they see this number.

A traditional 401(k) allows employees to make their own deferrals and gives the employer flexibility in the matching formula, but it requires annual ADP/ACP nondiscrimination testing. The ADP test compares the deferral rate of HCEs to the deferral rate of non-highly compensated employees (NHCEs). If the HCEs defer at a much higher rate than the rank-and-file (which is common in construction, where field workers often decline to participate), the plan fails the test and the HCE contributions must be reduced or refunded. This is a frequent problem in construction: the owner wants to max out deferrals, but the crew does not participate, and the ADP test limits what the owner can defer.

The Safe Harbor 401(k) solves the ADP/ACP testing problem. Under IRC 401(k)(12), a Safe Harbor plan satisfies nondiscrimination automatically if the employer makes one of two contributions: a 3% non-elective contribution to all eligible employees (whether or not they defer), or a matching contribution of 100% on the first 3% of compensation deferred plus 50% on the next 2%. The Safe Harbor contribution is immediately 100% vested. In exchange, the owner can defer the full $23,500 ($31,000 or $34,750 with catch-up) regardless of employee participation rates.

The cost of the Safe Harbor contribution is predictable: for a company with $500,000 in eligible employee wages, the 3% non-elective Safe Harbor costs $15,000 per year. That $15,000 buys the owner unrestricted access to the full deferral limit, plus the employer profit-sharing contribution on the owner’s salary. For most construction companies with 5-20 employees, the Safe Harbor 401(k) is the right plan.

How do I maximize contributions when income is seasonal?

Construction income is rarely steady. Revenue concentrates in certain months depending on geography and trade: exterior work drops in northern winters, hurricane season slows coastal projects, and the bidding cycle creates feast-or-famine quarters. The retirement plan must accommodate this pattern.

The solo 401(k) and Safe Harbor 401(k) offer the most flexibility. Employee deferrals can be adjusted throughout the year (the owner can increase the deferral percentage during high-revenue months and reduce it during slow months), and the employer profit-sharing contribution can be made in a lump sum after year-end, up to the tax return filing deadline including extensions. This means a construction owner who has a strong September through December can wait until the following March or even September (with an extension) to determine the optimal employer contribution based on actual full-year income.

The SEP-IRA has the same post-year-end flexibility for contributions (contributions are due by the filing deadline including extensions), but the contribution percentage must be uniform for all employees, so the owner cannot fine-tune the amount without affecting employee costs.

For construction businesses with highly variable income, cash flow management around retirement contributions matters as much as the plan type. Owners should set aside estimated retirement contributions monthly (even if the actual contribution is made annually), treating the retirement contribution as a fixed cost in the job costing system rather than an afterthought. This is particularly important for companies that carry retainage receivables, where cash collections lag revenue recognition and a large year-end contribution could create a liquidity squeeze.

When does a defined benefit or cash balance plan fit?

For construction owners age 45+ with consistently high income ($300,000+ net of business expenses), a cash balance defined benefit plan stacked on top of a 401(k) can push total annual tax-deferred contributions well beyond $100,000. A cash balance plan defines the benefit as a hypothetical account balance credited with annual contributions and a stated interest rate. The actuary determines the required annual contribution based on the owner’s age, target benefit, and years to retirement. Under IRC 415(b), the maximum annual benefit payable from a defined benefit plan is $280,000 for 2025, and the contribution needed to fund that benefit increases dramatically with age (because older participants have fewer years of growth to reach the target).

Approximate annual cash balance contributions by age (2025, illustrative): age 40 runs $80,000-$110,000; age 45, $110,000-$150,000; age 50, $150,000-$200,000; age 55, $200,000-$280,000; age 60, $280,000-$350,000+. These are in addition to the 401(k) contribution, so a 55-year-old construction company owner could potentially defer $270,000-$360,000 in a single year between both plans.

The catch for construction companies is income volatility. A cash balance plan creates a mandatory annual funding obligation. Once the plan is established and the benefit is promised, the employer must make the actuarially required contribution each year, regardless of business conditions. A contractor who commits to a $200,000 annual cash balance contribution and then has a $150,000 income year faces a serious problem. The plan can be amended to reduce future benefit accruals, but contributions for benefits already accrued cannot be skipped without triggering penalties and potential plan termination. Construction owners considering a cash balance plan should have at least three to five years of consistently high income behind them and a pipeline that supports the contribution level going forward. The plan should be designed conservatively, with the actuarial assumptions leaving room for income fluctuations.

If the company has employees, the cash balance plan must cover them under the same nondiscrimination rules that apply to the 401(k). The actuary designs the employee benefits to satisfy testing at the lowest possible cost, but employee contributions of 5-7% of covered compensation are typical. For a company with a large field crew, this cost can add up. Cross-testing (comparing benefits on an equivalent-benefit basis rather than a contribution basis) can reduce the employee cost, but the actuarial fees for a cash balance plan ($2,000-$5,000 annually) are an additional expense.

What did SECURE 2.0 change for contractors?

The SECURE Act 2.0 (enacted December 2022) made several changes relevant to construction company owners. The most significant is the “super catch-up” for ages 60 through 63: starting in 2025, participants who are 60, 61, 62, or 63 years old can make a catch-up contribution of $11,250 (instead of the standard $7,500 catch-up for age 50+), bringing the total elective deferral to $34,750. For a construction owner in that age window, this adds $3,750 in additional deferral capacity compared to the standard catch-up.

Other SECURE 2.0 provisions that matter for contractors: employer matching and profit-sharing contributions can now be designated as Roth (after-tax, tax-free at withdrawal) starting in 2024, though this is more useful for owners who expect to be in a higher tax bracket in retirement. The starter 401(k), a new plan type with automatic enrollment and a $6,000 deferral limit, is aimed at employers who want to offer a plan with minimal cost, but the low deferral limit makes it irrelevant for owner-operators seeking maximum contributions. Small employer tax credits for new plan establishment (up to $5,000 per year for three years for businesses with up to 50 employees) can offset the startup cost of a Safe Harbor 401(k) or cash balance plan, which is particularly helpful for construction companies adopting their first formal retirement plan.

How do I choose the right plan?

The decision tree starts with two questions: does the business have employees, and how much does the owner want to contribute?

For a solo owner with no employees earning $150,000+, the solo 401(k) beats the SEP-IRA in almost every scenario because of the employee deferral component and catch-up eligibility. Add a cash balance plan if the owner is 45+ and income consistently exceeds $300,000.

For an owner with employees, the Safe Harbor 401(k) is the default recommendation. The 3% non-elective contribution is a predictable cost that unlocks full owner deferrals without the risk of failed ADP/ACP testing. Layer the employer profit-sharing contribution on top (the profit-sharing contribution can be allocated using a “new comparability” formula that favors the owner, subject to nondiscrimination testing on the profit-sharing component). Add a cash balance plan if the owner is 45+, income is stable, and the employee coverage cost is manageable.

For companies operating across multiple states, the retirement plan deduction interacts with state income tax apportionment, and the employer contributions for employees in different states may need to be tracked separately for state payroll tax purposes. Bonding and insurance costs are unaffected by retirement plan contributions, but the cash flow impact of a large annual contribution should be modeled alongside bonding capacity and insurance premiums, especially for firms bidding on prevailing wage projects where fringe benefit obligations already include retirement contributions credited toward the prevailing wage rate.

The plan should be established before December 31 of the year the owner wants to begin making employee deferrals (employer profit-sharing contributions for a new plan can still be made up until the filing deadline for that first year). Working with an actuary or third-party administrator who understands construction industry cash flow patterns is important, particularly for cash balance plans where the annual funding commitment must be sustainable through the business cycle.

Related guides:

• Construction Change Order Management Revenue Recognition
• Construction Contractor Tax Deductions Wip Accounting
• Construction Entity Structure Llc Scorp Qbi Deduction
• Construction Equipment Section 179 Bonus Depreciation
• Construction Insurance Bonding Surety Tax Treatment

Related guides:

• Cash Balance Pension Plans: How High-Income Business Owners Can Defer $200,000+ Per Year in Tax-Deductible Retirement Contributions

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