How to Set Up a 401(k) for Your B2B SaaS Startup in 2026
The SECURE Act 2.0 created a 401(k) startup tax credit so generous that, for companies with under 50 employees, the plan is effectively free to administer for three years. Most founders don't know this. They delay setting up a 401(k) because they assume it's expensive and complicated. It is neither — and delaying it costs you candidates every time a competing offer includes a match and yours doesn't. Here's how to do it right.
Before You Start — What You Need in Place
You need three things before you can set up a 401(k):
- A payroll platform — Gusto, Rippling, Justworks, or similar. The 401(k) provider needs to sync with payroll to process deferrals automatically.
- An EIN — obvious, but the plan is established in your company's name under your federal tax ID.
- A decision on plan design — specifically, whether to do a Safe Harbor plan (recommended for most startups) or a traditional 401(k). More on this below.
You do not need an HR team, a broker, or a CFO to set this up. At under 25 employees, a founder can do it in an afternoon.
Step 1: Understand the Tax Credits You're Leaving on the Table
SECURE Act 2.0 changed the economics of small employer retirement plans starting in 2023. If you have 50 or fewer employees and haven't started a 401(k) in the past three years, you're eligible for:
- Startup credit: 100% of qualified plan startup and admin costs, up to $5,000/year, for 3 years
- Auto-enrollment credit: additional $500/year for 3 years when you add automatic enrollment
- Employer contribution credit: up to $1,000 per employee per year for employer contributions, phased over 5 years (100%/100%/75%/50%/25%)
At 15 employees, this means your 401(k) admin costs can be entirely offset by federal tax credits for the first three years — while you're also getting a credit on the contributions you make. There is no rational argument for waiting.
Step 2: Choose Your Plan Design
Most startups should use a Safe Harbor 401(k). Here's why.
Without Safe Harbor, the IRS runs annual ADP/ACP nondiscrimination tests to ensure that highly compensated employees (HCEs — generally anyone earning $155k+ or owning 5%+ of the company) aren't getting disproportionate retirement benefits relative to non-HCEs. If you fail, HCEs receive taxable refunds of excess contributions. For a startup where the founders and early employees are all HCEs, this is nearly guaranteed to be a problem.
Safe Harbor eliminates the tests entirely, in exchange for a required employer contribution that vests immediately:
| Safe Harbor design | What you contribute |
|---|---|
| Basic match | 100% of first 3% + 50% of next 2% = effective 4% max |
| Enhanced match | 100% of first 4% of salary deferred |
| Nonelective | 3% of compensation to all eligible employees regardless of deferral |
The nonelective design is the cleanest: everyone gets 3%, whether they contribute or not. It's the strongest recruiting signal and the simplest to administer. The basic match is the most common in practice because it only costs you money when employees participate.
Employee deferral limits for 2025: $23,500 standard; $31,000 for employees age 50+.
Step 3: Pick the Right Provider for Your Payroll Platform
This decision is simpler than it looks — and one critical thing has changed in the last two years.
| Your payroll platform | Recommended 401(k) provider | Why |
|---|---|---|
| Gusto | Guideline | Native integration post-acquisition; lowest employee expense ratios (~0.08%); manages ERISA fiduciary for you |
| Rippling | Vestwell or Human Interest | Guideline–Rippling integration was broken when Gusto acquired Guideline in 2024; do not use Guideline on Rippling |
| Justworks | Guideline (standalone) or Justworks bundled | Check pricing — Justworks bundles a 401(k) option but it may cost more than standalone Guideline |
| Any platform | Avoid Betterment at Work | Higher employee-side expense ratios; no material advantage over Guideline or Vestwell |
The expense ratio difference matters more than founders realize. An employee-side expense ratio of 0.08% vs. 0.45% compounds significantly over 20–30 years of retirement saving. It is a real cost that shows up in your team's retirement balances, not yours.
Step 4: Set Your Match and Add Auto-Enrollment
What match to offer by stage:
| Stage | Typical match | Annual cost on $1M payroll |
|---|---|---|
| Bootstrapped / pre-seed | None | $0 |
| Seed | None or 2–3% | $20k–30k/yr at 3% |
| Series A | 3–4% (Safe Harbor basic) | $35k–40k/yr |
| Series B+ | 4–6% with vesting schedule | $50k–60k/yr |
72% of Series A SaaS companies in our survey offer some match, with a median of 3.5%. If you're closing Series A and don't have a match, you will lose candidates to companies that do.
Auto-enrollment: For any plan established after December 29, 2022, SECURE Act 2.0 requires auto-enrollment once you're past the three-year exemption window and have more than 10 employees. Even before it's required, auto-enrollment materially increases participation rates — and the $500/year tax credit makes adding it a no-brainer.
Step 5: Know When You'll Hit the ERISA Audit Threshold
Once you have 100 or more participants with account balances at the start of a plan year, you must file a large-plan Form 5500 and engage an independent ERISA auditor. The audit runs $5,000–$15,000 per year — a real line item, but not a reason to avoid the plan. It's a reason to model when you'll cross the threshold.
For a 40-person company growing at 30% annually, that's roughly three years away. Start tracking participant counts now so you're not surprised.
Common Mistakes Founders Make
- Waiting until Series A to set up the plan — you lose three years of startup tax credits and give up recruiting leverage at seed
- Using Guideline on Rippling — the integration is broken; your payroll syncs will fail
- Skipping Safe Harbor — nondiscrimination test failures at a 15-person company where every employee is an HCE are almost certain without it
- Setting a match but not a vesting schedule — a 4-year graded vesting schedule with a 1-year cliff is standard at Series B+; at Series A, immediate vesting is more competitive and simpler to administer
- Not auto-enrolling — participation rates are 20–30 percentage points higher with auto-enrollment; and you get a $500/year tax credit for adding it
How a Fractional Finance Team Can Help
The 401(k) setup itself is straightforward. The harder questions are the ones around it: how does the employer contribution credit interact with your R&D tax credit strategy? When should you move from SIMPLE IRA to Safe Harbor 401(k)? How do you model the cost of a 3% nonelective contribution against your current burn rate? Bridges helps Series A SaaS companies answer these questions as part of a broader benefits cost model — so the 401(k) decision is made in the context of your full comp and cash flow picture, not in isolation. Reach out if you're approaching the setup decision or approaching 100 participants.
