Safe Harbor Contribution Deadlines: What Plan Sponsors Need to Know and Do to Ensure Compliance

Safe Harbor 401(k) plans offer a powerful benefit: they allow employers to avoid annual non-discrimination testing, a challenge that disproportionately affects privately held and smaller organizations with a higher concentration of highly compensated employees. But while Safe Harbor can solve major testing headaches, the relief only works if employers meet the IRS’s rules—especially the contribution and notice deadlines that come around every year.

And because those deadlines arrive earlier than many plan sponsors expect, it’s surprisingly easy to miss them without deliberate, proactive planning.

Many employers have already passed the key Safe Harbor deadlines for this plan year. But that makes now the perfect time to ensure you don’t find yourself in the same rushed position again…and to revisit whether you’re using Safe Harbor in the most strategic way to support participation goals, testing outcomes, and overall plan health.

Safe Harbor Refresher: Why These Deadlines Matter

A Safe Harbor plan design exempts employers from annual non-discrimination testing—tests that often limit how much highly compensated employees (HCEs) can contribute when the rest of the organization isn’t contributing enough to balance the plan.

For organizations that have ever experienced a failed test or issued refunds to HCEs, Safe Harbor is frequently the most direct and reliable solution. But it comes with conditions, primarily around when contributions must be made and when required notices must be delivered.

Missing these deadlines isn’t just an administrative inconvenience. It can result in:

• Loss of Safe Harbor status for the entire plan year
• Required corrective contributions
• Potential excise taxes
• Reversion to non-discrimination testing (and all the problems that come with it)

The deadline calendar matters because Safe Harbor elections aren’t retroactive. You can’t wait until the plan year is underway and then decide to add the match as a fix (at least not for most Safe Harbor options).

Payroll-to-Payroll vs. Post-Year-End Contributions

Most employers with Safe Harbor provisions fund required contributions each payroll period, whether they use the traditional Safe Harbor match or the 3% non-elective contribution. Payroll-to-payroll funding is the cleanest and most common method; it’s predictable, it satisfies the rules, and it minimizes risk.

But some employers prefer (or need) to wait until after the year ends to make their contributions, especially when:

• cash flow varies throughout the year;
• profit sharing is also being evaluated; or
• they want to calculate contributions based on finalized year-end numbers

In those scenarios, Safe Harbor contributions (if not made payroll-to-payroll) must be deposited no later than the employer’s corporate tax-filing deadline, including any extensions.

For a calendar-year fiscal schedule, for example:

• Original filing deadline: April 15
• Extended filing deadline: October 15

If an organization files for an extension, the Safe Harbor contribution deadline automatically extends with it. But regardless of your tax strategy, missing this date brings you right back into testing for the plan year you thought you had protected.

Plan Ahead: The October 1 Safe Harbor Match Deadline

If an employer wants to adopt the traditional Safe Harbor match for the upcoming plan year, typically structured as:

• 100% match on the first 3% deferred
• 50% match on the next 2% deferred
• (For a total employer commitment of up to 4% when an employee contributes 5%)

…the election must be in place no later than October 1 preceding the plan year.

This is one of the deadlines that comes faster than many employers expect.

If you wanted the match for the 2026 plan year, for example, the election needed to be finalized by October 1, 2025. If you missed it, you can’t retroactively decide to use this match structure. The IRS does not allow a look-back match to qualify for Safe Harbor.

This one date alone is the reason many plan sponsors scramble…and why proactive planning with your consultant matters so much.

The Backup Option: 3% Non-Elective Contribution (Thanks to SECURE and SECURE Act 2.0)

SECURE and SECURE Act 2.0 introduced an important safety valve: the ability to adopt the 3% non-elective Safe Harbor contribution with just 30 days’ notice.

That means a calendar-year plan sponsor has until December 1 to put a Safe Harbor non-elective in place for the current plan year, and apply it retroactively to the beginning of the plan year.

This gives plan sponsors more flexibility to reassess their plan design late in the year, especially if testing issues arise or participation rates shift.

But the non-elective contribution is still a real financial commitment. And if December 1 passes without action, you’ve officially lost your ability to fix testing problems through Safe Harbor for the current plan year.

Annual Safe Harbor Notices: Don’t Overlook This Step

Every Safe Harbor matching plan (new or existing) must distribute an annual Safe Harbor notice to plan participants at least 30 days before the start of the plan year. (Under the SECURE Act, if a plan sponsor is using the Safe Harbor non-elective formula alone, the standard 30-90 day pre-year Safe Harbor notice is no longer required).  

For calendar-year plans, that means notices are due by December 1 each year. The notice informs participants:

• which Safe Harbor provision the plan uses;
• how the match and non-elective contribution works;
• any additional employer contributions; and
• eligibility and vesting details

Many employers assume their recordkeeper is handling this, and many recordkeepers do…but not all, and not consistently. We routinely encounter new clients whose prior advisors or vendors failed to ensure notices went out on time.

Missed notices are surprisingly common. And while they’re not always immediately detected, they can jeopardize Safe Harbor status if discovered during an audit.

Deadlines for This Year May Have Passed—Exactly Why You Plan Now

By the time many employers think about Safe Harbor, it’s already late in the year. That’s why we see:

• match deadlines missed
• non-elective deadlines nearly missed
• notices overlooked
• testing issues discovered too late

If that happened to you this year, you’re not alone. But it’s also a sign that your consultant isn’t doing enough to help you plan proactively. Deadlines don’t sneak up on plan sponsors who have a structured annual planning process.

Now—right after this year’s deadlines—is the ideal moment to evaluate:

• Did we miss anything? ‍
• Do we expect testing problems next year? ‍
• Is Safe Harbor still the best strategy for our workforce and participation levels? ‍
• Should we be discussing this in Q2 or Q3 instead of scrambling in September?

A Proactive Consultant Keeps You Ahead of the Calendar

When we work with clients, this is built into an annual cycle of review, planning, and communication. You shouldn’t be discovering deadlines — you should be prepared for them. Safe Harbor deadlines are just one piece of a much larger compliance, planning, and fiduciary oversight landscape.  

Working with a consultant who:

• Keeps you informed months in advance
• Reviews testing projections
• Guides plan design decisions
• Confirms that notices go out
• Ensures contributions are made correctly
• Coordinates with recordkeepers and payroll

…means you won’t be relying on last-minute fixes or scrambling to solve problems after the fact.

If you’ve ever missed a Safe Harbor deadline — or didn’t even know there were deadlines — that’s a sign you need a more strategic partner.

Let’s Make This Year the Smoothest One Yet

The most effective Safe Harbor strategy is one that’s discussed well before the fourth quarter. If you’re unsure whether you’re on track, or whether Safe Harbor is even the right design for your plan, let’s talk now, while you still have maximum flexibility.