A new safe harbor 401(k) has to be in place and running for at least three months of the plan year, which means October 1 is the practical cutoff for a calendar-year business. At Lewis Group CPAs, we have been advising business owners in Vancouver, Camas, Washougal, Battle Ground, La Center, Longview, and across Clark and Cowlitz counties since 1994, and this is one of the few deadlines where a two-week delay costs you an entire tax year of retirement deductions.
What Is a Safe Harbor 401(k)?
A safe harbor 401(k) is a standard 401(k) plan in which the employer commits to a required annual contribution for eligible employees, and in exchange the plan automatically passes the IRS nondiscrimination tests that otherwise limit how much owners and highly paid employees can contribute.
The required contribution takes one of two standard forms:
- A match. 100% of the first 3% of pay each employee defers, plus 50% of the next 2%. An employee deferring 5% or more receives 4% of pay; an employee deferring nothing receives nothing.
- A nonelective contribution. A flat 3% of pay to every eligible employee, whether or not they defer anything.
“Safe harbor” is a design choice, not a brand of plan. The accounts, deferral limits, and investment options are the same as any 401(k); the required contribution is the price of the automatic testing pass. Without it, annual testing caps owner and highly-paid-employee contributions based on what everyone else defers, and in a small company where few employees defer much, that cap lands low. For an owner with a handful of employees, safe harbor status is usually the difference between deferring a token amount and deferring the full annual limit. The IRS adjusts contribution limits each year, and you can check the current figures on the IRS cost-of-living adjustment page for retirement plans.
Why October 1 Matters So Much
The IRS treats a first-year safe harbor 401(k) as legitimate only if it covers a meaningful stretch of the plan year. Three months is the standard, and that math lands you on October 1 for a December 31 year end. The IRS lays out the basics in its 401(k) plan overview for sponsors and in Publication 4222, 401(k) Plans for Small Businesses.
Here is the part owners tend to miss. Employee deferrals, including yours, can only come out of pay you earn after your election is on file. You cannot go back in November and decide to defer from June’s paycheck. So if the plan is not live, the deferral opportunity for every paycheck already cut is permanently lost, and the employer contribution you were counting on gets pushed into the following tax year.
The Late-Adoption Route Exists, and Here Is What It Costs
There is a legal way to add safe harbor status late, and it is worth knowing exactly what it buys and what it does not. Since the SECURE Act, a plan can adopt a nonelective safe harbor design (a flat employer contribution to every eligible employee, whether or not they defer) retroactively for the year:
- At the standard 3% of compensation, the amendment can be adopted up to 30 days before the end of the plan year.
- After that, the amendment can still be adopted as late as the last day of the following plan year, but the required contribution rises to 4% of compensation for every eligible employee.
The SECURE Act also removed the advance notice requirement for nonelective safe harbor plans, which is what makes the late adoption workable at all.
Two limits keep this from being a rescue. First, it applies cleanly to existing 401(k) plans adding safe harbor status; whether a brand-new plan can use it is less settled, because the three-month first-year requirement likely still applies. Second, no version of it recovers employee deferrals from paychecks that have already been issued. The late route buys the nondiscrimination pass at a higher employer cost. It does not buy back your own missed deferrals. That is why October 1 remains the date to plan around.
The Notice Requirement Moves Your Real Deadline Earlier
Safe harbor plans that use a match require written notice to eligible employees. For an ongoing plan, the standard window is 30 to 90 days before the plan year begins. For a first-year plan, the requirement is that the notice reaches employees before deferrals begin, which for an October 1 start means the notice, the plan document, the payroll integration, and the recordkeeper’s onboarding queue all have to be done in September. August is when this work realistically starts. September calls are doable. Late September calls are tight.
Nonelective safe harbor plans no longer require the notice, but the payroll and recordkeeper lead times apply either way.
New Plans Now Include Automatic Enrollment, Unless You Are Exempt
A rule from the SECURE 2.0 Act applies to plans established after December 29, 2022: starting in 2025, new 401(k) plans must automatically enroll eligible employees. The default deferral starts between 3% and 10% of pay and increases 1% each year until it reaches at least 10%. Employees can opt out at any time.
The exemptions cover a lot of our clients. Businesses that normally employ 10 or fewer people are exempt. So are businesses less than three years old, along with church and governmental plans. If your crew is larger than 10, plan on automatic enrollment being part of the design, and make sure your payroll process can handle default deferrals and annual escalation from day one. It also earns a tax credit, covered below.
If You Already Have a SEP or a SIMPLE
Plenty of owners open a SEP IRA because it takes ten minutes, then never revisit it. A SEP is funded entirely by the employer, so if you have employees, every dollar you put away for yourself comes with proportional dollars for them. A 401(k) shifts a large share of the funding to employee deferrals, which changes the economics considerably once you have a payroll.
If you have a SIMPLE IRA, the SECURE 2.0 Act opened a door that used to be shut: a SIMPLE IRA can now be replaced mid-year with a safe harbor 401(k) under specific conditions, rather than waiting for January. The rules around the timing, the prorated contribution limits, and the rollover treatment of existing SIMPLE balances are particular, so this is a conversation to have with your accountant before you sign anything. The IRS summary of the SECURE 2.0 provisions is a reasonable starting point.
High Earners: Stacking a Cash Balance Plan on Top
If your business consistently produces strong profit and you are within fifteen or so years of retirement, a 401(k) alone may not absorb what you actually want to set aside. A cash balance plan, which is a defined benefit plan expressed as a hypothetical account balance, can be paired with the 401(k) and profit sharing to support deductions well into six figures, with the exact amount driven by your age, compensation, and the employee census.
Two timing notes. The 401(k) side still wants that October 1 start. The cash balance design work, including the actuarial numbers and the plan document, takes weeks, and the deduction depends on funding the contribution by your filing deadline including extensions. Starting that conversation in the fourth quarter of the year you want the deduction is uncomfortably late.
You can read more about how we approach plan selection and coordination on our Retirement Plans page.
Don’t Overlook the Startup Credits
New plans are cheaper to launch than most owners expect, and the credits are specific:
- Startup cost credit. Employers with 50 or fewer employees can claim 100% of eligible plan administration costs, up to $5,000 per year for the first three years. Employers with 51 to 100 employees claim 50% of costs against the same cap.
- Automatic enrollment credit. An additional $500 per year for the first three years the plan includes an automatic enrollment feature. New plans generally include the feature by law now, and the credit still applies.
- Employer contribution credit. A separate credit based on employer contributions, up to $1,000 per employee, phasing down over five years and reduced for employers with 51 to 100 employees.
Details and eligibility are on the IRS page covering the retirement plans startup costs tax credit. These credits reduce tax dollar for dollar, which is a better outcome than a deduction of the same size, and together they are often enough to cover the first years of administration.
What We Handle, and What You Need to Bring
We work with business owners who need both the business return and the personal return handled by one firm, because a retirement plan decision touches both. Your entity type, W-2 wages, distributions, spousal income, and employee census all feed the same answer. We have five licensed CPAs on staff and are members of the Washington Society of CPAs, the Oregon Society of CPAs, and AICPA & CIMA, and we work with clients on both sides of the river.
To size a plan properly, we generally need current-year profit projections, your payroll register, an employee list with dates of hire and hours, and details on any existing SEP, SIMPLE, or 401(k). You can send all of it through our secure client portal, which tracks the documents we still need so nothing sits in an email thread.
If October 1 is anywhere near your radar this year, contact us now rather than in the fall. We would rather tell you a 401(k) is not the right fit in August than explain in December why the deduction has to wait until next year.
