The October 1st Retirement Deadline Most LA Business Owners Will Miss
By The Tax Shack | September 2026 | Los Angeles, CA
If you have employees and you want to max out your own retirement contributions this year without IRS restrictions, there's a deadline coming up most small business owners don't know exists.
October 1, 2026. After that date, you can no longer start a Safe Harbor 401(k) for the 2026 plan year.
Here's what a Safe Harbor 401(k) is, why it matters specifically for LA business owners, and what you need to do before the deadline.
The Problem With a Regular 401(k) If You Have Employees
A standard 401(k) sounds simple in so far as you set it up, contribute, and that’s that. But if you're a business owner or highly compensated employee (HCE), there's a catch: the IRS requires that highly paid staff can't contribute dramatically more than rank-and-file employees as a percentage of salary.
Every year, the IRS runs two tests:
ADP test (Actual Deferral Percentage): Compares average deferral rates of highly compensated employees vs. everyone else. If the gap is too large, the IRS forces refunds of contributions back to the owner which are taxable, after the fact.
ACP test (Actual Contribution Percentage): The same logic applied to employer matching contributions.
In practice, this means a business owner whose employees aren't participating much in the 401(k) can get hit with a surprise tax bill in the spring when their own contributions get partially refunded. This is obviously not ideal.
A Safe Harbor 401(k) eliminates both tests entirely. (IRS, IRC §401(k)(12))
What Makes a Plan "Safe Harbor"
To qualify, your plan must meet one of three mandatory employer contribution formulas and all of them vest immediately for employees:
Option 1 — Basic Match: 100% match on the first 3% of employee salary deferred, plus 50% match on the next 2%. Costs you 4% of an employee's salary when they defer 5% or more.
Option 2 — Enhanced Match: At least as generous as the basic match, with various structures like for example, 100% match on the first 4% deferred.
Option 3 — Non-Elective Contribution: You contribute 3% of every eligible employee's salary, regardless of whether they contribute anything themselves.
The tradeoff is you're committing to a mandatory employer contribution. In exchange, you get to contribute the full IRS limit yourself with no ADP/ACP testing, no year-end surprises. (IRS, Safe Harbor 401(k) Plans)
The 2026 Numbers
Here's what the contribution limits look like for 2026: (IRS IR-2025-111)
Employee deferral limit: $24,500
Catch-up contribution (ages 50–59 and 64+): $8,000
Super catch-up (ages 60–63, new under SECURE 2.0): $11,250 — this is the one people miss
Total combined limit (employer + employee): $72,000
For a 60-year-old business owner, that's a potential $35,750 in personal contributions ($24,500 + $11,250) that are all pre-tax, all deductible.
At California's 9.3% state rate plus a 32% federal rate, maxing those contributions could mean over $14,000 in combined tax savings in a single year. That's before the employer contribution deduction.
The Super Catch-Up Most Owners Don't Know About
SECURE 2.0 created a special catch-up limit for employees aged 60, 61, 62, or 63. This is $11,250 in 2026 vs. $8,000 for all other catch-up eligible ages.
Most plan documents haven't been updated to reflect this. If you or a key employee falls in this age range, confirm your plan document explicitly allows the Section109 super catch-up. An outdated document means you can't use it even if you're otherwise eligible. (U.S. Department of Labor, 401(k) Plans for Small Businesses)
The SECURE 2.0 Tax Credits (Free Money for Starting a Plan)
If you don't have a 401(k) yet, the federal government is essentially paying you to start one.
Under SECURE 2.0, employers with fewer than 50 employees can claim:
Startup cost credit: Up to 100% of plan startup costs (administration, setup) for the first three years, up to $5,000 per year
Employer contribution credit: Up to $1,000 per employee per year (for employees earning under $100,000) for the first five years, decreasing each year
Combined, eligible businesses can receive up to $16,500 in federal tax credits during the first few years of a new plan. (ForUsAll, Safe Harbor 401(k) Guide 2026)
The California Specifics
A few things California business owners specifically need to know:
The good news is 401(k) employer contributions are deductible on both your federal and California state returns. Unlike HSAs (which California doesn't recognize), traditional 401(k) contributions reduce your California taxable income. (SWAT Advisors, California Tax Planning 2026)
The catch on withdrawals is California taxes 401(k) distributions as ordinary income at state rates, up to 13.3%, with no retirement income exemption. If you withdraw before 59½, you face the federal 10% penalty plus California's full income tax rate on top. Roth distributions are the exception and qualified Roth withdrawals are tax-free at both the federal and state level. (Negozee, 401(k) in California 2026)
CalSavers compliance: California mandates that employers with five or more employees either enroll in CalSavers (the state-run plan) or offer a qualifying retirement plan. A Safe Harbor 401(k) satisfies this requirement, and is significantly more flexible and generous than CalSavers. If you have employees and no plan, you're likely already out of compliance. (CalSavers)
The Roth catch-up mandate: Beginning in 2026, employees who earned more than $150,000 from your business in the prior year must make their age-based catch-up contributions as Roth (after-tax) contributions. If your plan doesn't offer a Roth feature, those employees can't make catch-up contributions at all. Get your plan document updated before this creates a compliance issue. (IRS, SECURE 2.0 Guidance)
Is a Safe Harbor 401(k) Right for Your Business?
It usually makes sense if:
You're a profitable S-Corp or LLC owner with employees who aren't maxing out contributions
You've had your 401(k) contributions partially refunded due to failed ADP testing
You want to contribute the maximum possible to your own retirement
You're between ages 60–63 and want the super catch-up benefit
You have 5+ employees and need to satisfy CalSavers compliance
It may not be the right fit if:
Your cash flow is unpredictable, as the mandatory employer contribution is a fixed obligation
You're solo with no employees, as a Solo 401(k) or SEP-IRA is simpler and often just as effective
Your employees earn too much, as the employer contribution cost scales with payroll
The October 1st Deadline
A new Safe Harbor 401(k) for the 2026 calendar year must generally be effective by October 1, 2026, as the plan needs to run for at least three months of the year. Match-based plans also require a notice to employees at least 30 days before the plan year begins, so the real action deadline is earlier than it looks. (IRS, Safe Harbor 401(k) Plans)
If you miss October 1, you're looking at 2027. That's another full year of leaving significant retirement deductions and potential tax savings on the table.
What This Means for LA Business Owners
The Safe Harbor 401(k) sits at the intersection of two things The Tax Shack spends a lot of time on: minimizing what you pay in taxes and building a plan that works for you year-round, not just at filing time.
Combined with the PTET election we've covered in a separate post, a maxed Safe Harbor 401(k) is one of the most powerful one-two punches available to a profitable LA business owner. One reduces your federal income tax via entity-level deduction. The other shelters up to $35,750 of your personal income. Both are available to you before December 31.
At The Tax Shack, our CTEC-certified preparers work with LA business owners year-round on exactly this kind of planning. If you want to know whether a Safe Harbor 401(k) makes sense for your business before October 1, stop by our Los Angeles location or give us a call.
Quick-Answer FAQ
What is a Safe Harbor 401(k)? A retirement plan design that meets IRS mandatory contribution requirements, automatically exempting the plan from ADP and ACP nondiscrimination testing. Owners and highly compensated employees can contribute the full IRS limit without restriction. (IRS)
What is the deadline to start a Safe Harbor 401(k) for 2026? October 1, 2026 for new calendar-year plans. The plan must be in effect for at least three months of the plan year. (IRS IR-2025-111)
What are the 2026 401(k) contribution limits? $24,500 employee deferral limit. $8,000 catch-up for ages 50–59 and 64+. $11,250 super catch-up for ages 60–63. $72,000 total combined limit including employer contributions. (IRS IR-2025-111)
Are 401(k) contributions deductible in California? Yes. traditional 401(k) employer and employee contributions reduce both federal and California taxable income. Unlike HSAs, California conforms to federal 401(k) deduction rules. (SWAT Advisors)
What is the CalSavers requirement for California employers? California employers with five or more employees must either enroll in CalSavers or offer a qualifying retirement plan. A Safe Harbor 401(k) satisfies this requirement. (CalSavers)
What is the super catch-up contribution for 2026? Employees aged 60–63 can contribute an additional $11,250 in catch-up contributions in 2026, compared to $8,000 for all other catch-up eligible ages. This was created by SECURE 2.0 and requires an updated plan document to use. (U.S. Department of Labor)
Sources: IRS, Safe Harbor 401(k) Plans; IRS IR-2025-111, 2026 Retirement Plan Limits; U.S. Department of Labor, 401(k) Plans for Small Businesses; CalSavers; ForUsAll, Safe Harbor 401(k) Guide 2026; Negozee, 401(k) in California 2026; SWAT Advisors, California Tax Planning 2026.
This post is for general informational purposes and is not a substitute for personalized tax or financial advice.
