The question of the ideal group captive company size comes up more than almost any other. An HR director at a 95-person manufacturer wants to know if her company is too small. A CFO at a 900-person services firm wonders if his company is too large. Both are focused on headcount, and headcount is the wrong lens.
Size is a starting point, not a verdict. What actually determines whether a group medical captive makes sense for your company is the underlying financial logic: how much you’re overpaying for certainty you’re not actually receiving, and how much risk you’re absorbing with nothing to show for it. Once you understand that, the size question answers itself.
What Group Captive Company Size Is Really About
With a fully insured plan, you pay a fixed premium every month regardless of what your employees actually use. The carrier keeps the spread between what you pay and what gets spent on claims. In a good year, that margin goes straight to their bottom line. You get nothing back.
A group medical captive flips that structure. Roughly 85% of your spend is variable rather than fixed. You self-fund the routine claims layer, contribute to a shared risk pool with other employers in the captive, and buy stop-loss reinsurance to cap catastrophic exposure.
At the end of the plan year, any unused funds in the shared risk pool are returned to members on a pro-rata basis. Roundstone has returned $91.8 million in unused premiums to its members since the program’s inception.
The captive isn’t a workaround for employers who can’t afford real insurance. It’s the structure that Fortune 500 companies have used for decades to capture the economics of self-funding. Roundstone makes that same structure available to employers with 25 to 1,000 employees.
Learn how fully insured carriers keep you in the dark and why it’s costing you money.
The 25- to 100-Person Employer
The most common objection at this size is volatility. One catastrophic diagnosis, one premature birth, one employee with a complex chronic condition, and the math looks terrifying on a solo self-funded basis. That concern is legitimate. It’s also exactly what the captive is built to neutralize.
When you self-fund inside Roundstone’s captive, you don’t absorb your own volatility in isolation. Your specific stop-loss insurance coverage puts a ceiling on what any single claim can cost you. Above that, the captive’s shared risk pool, which is funded by hundreds of participating employers like you, absorbs the pressure.
Above the captive layer, reinsurance coverage begins at $500,000 and goes up without limit. The result is that a 100-person company can carry the same risk architecture that a 10,000-person company has when it goes it alone.
The financial case at this size is also compelling. Roundstone members average roughly $12,385 per enrolled employee per year in total health plan costs. The national benchmark sits at $16,464.
Employers who adopt the Roundstone Preferred Bundle—which includes Bywater, Roundstone’s in-house third-party administrator (TPA), along with an integrated pharmacy benefits solution—will see even more cost savings; the average drops to approximately $10,810.
That’s a meaningful difference for a company that still thinks of health insurance as an uncontrollable line item.
Claims history matters, too. Underwriters look at your demographics, utilization trends, and risk profile to price the stop-loss policy. A company with a relatively healthy workforce and stable claims history will see that reflected in their pricing.
A company coming off two difficult plan years will, too, but the captive structure still offers more transparency and control than renewing a fully insured policy with a 20% increase and no explanation.
The 1,000-Person Employer
At this size, the question shifts. A company with 1,000 employees has enough claims volume to self-fund on a standalone basis, and many do. The relevant question switches from whether they can survive self-funding to whether they’re getting the most out of it.
Pure self-funding means you carry your own aggregate risk without a shared pool to spread it across. In a bad year, that’s entirely your problem. The captive changes that dynamic.
You’re pooled with other employers, so the financial exposure at the captive layer is distributed. You still benefit from your own good performance with Roundstone’s return of unused premiums pro-rata, but you’re not absorbing every adverse year by yourself.
At this size, the cost-containment infrastructure also matters more because there’s more to contain. Roundstone’s data analytics team gives larger employers real-time visibility into claims trends, pharmacy spend, high-cost claimants, and site-of-care opportunities.
Bywater handles clinical management and plan administration with the kind of integration that standalone TPAs rarely offer. For a company spending $10 million or more annually on health benefits, those tools are more than a nice-to-have.
There’s also a ceiling consideration. Employers at the upper end of the captive’s range sometimes wonder whether they’ve outgrown the model. The honest answer is that size alone doesn’t trigger that conversation; risk complexity does.
A 1,000-person employer with a straightforward claims profile benefits from the captive in ways a comparable standalone self-funded employer simply doesn’t.
CFOs: Get answers to the most pressing questions about self-funding through a group captive.
Is a Captive the Right Fit for a 1000- to 2500-Employee Company?
The question changes at this size. Roundstone’s group medical captive is built for employers with 25 to 1000 employees. Once a company moves above that range, the question becomes more case-specific.
A 1000- to 2500-employee company usually has enough claims volume to self-fund on its own. The data is more credible, the annual spend is larger, and the organization may already have a benefits team, advisor, TPA, and stop-loss structure in place. That doesn’t automatically mean a captive is off the table. It means the captive has to be evaluated for what it can still improve.
At this size, the conversation is less about gaining access to self-funding and more about whether the employer wants a better way to structure volatility, use claims data, and participate in the upside of better plan performance.
Potential Advantages
The advantages at this size come from leverage. A 1000- to 2500-employee company is already spending enough on healthcare for plan performance to matter, but it may still benefit from a structure that spreads volatility and rewards better claims management.
Potential Disadvantages
The disadvantages are mostly about fit and complexity. Larger employers may already have more mature funding strategies, vendor relationships, and internal benefits infrastructure, so the captive has to support the program rather than add unnecessary friction.
The Bottom Line
A 1000- to 2500-employee company is not the standard captive candidate in the same way a 25- to 1000-employee company is. The opportunity can still be real, but the answer depends on the employer’s current funding arrangement, claims history, stop-loss structure, and appetite for shared risk.
For companies in this range, the right next step is an underwriting and financial review. The question is not simply whether the company is too large. The better question is whether the captive structure would give the employer a smarter balance of control, risk protection, and long-term cost savings than its current approach.
Free download for HR professionals considering self-funding through a group captive.
What Headcount Can't Tell You
Two companies with 250 employees can be very different captive candidates. One has a relatively young workforce, low chronic disease burden, and a leadership team that wants to engage with claims data.
The other has an aging workforce, three or four high-cost claimants per year, and an HR team that treats the health plan as an administrative obligation. The captive works better for the first company. But it still works for the second, because the stop-loss structure limits the downside and the pool absorbs what the company can’t.
The factors that matter most in the fit assessment are your organization’s willingness to act on claims data, your appetite for moving from fixed to variable cost structure, your claims history over the past two to three years, and your advisor’s familiarity with self-funded models.
Headcount tells you whether you’re in the range. Those factors tell you whether the captive will perform.
The data-engagement piece is worth emphasizing. Roundstone’s data transparency gives employers monthly visibility into exactly where their health spend is going—by claim type, by provider, by employee cohort.
Companies that use that data to adjust plan design, steer members toward lower-cost care, and hold vendors accountable tend to see materially better results than those that treat the reports as background reading.
The captive’s financial structure creates the upside opportunity. Your engagement with the data is what captures it.
The Right First Step
If your company falls somewhere between 25 and 1,000 employees and you’ve been absorbing annual premium increases without a clear explanation of why, the captive warrants a serious look.
Roundstone’s group medical captive has been operating since 2005, and we built the model for exactly the range of employers that traditional self-funding has historically underserved.
Start with our self-insurance candidate checklist to see where your organization stands, or talk to a benefits advisor who can run your claims history against the captive’s underwriting criteria. The answer to “is this right for us” comes from that conversation, not from the number on your org chart.
Talk to a Roundstone Rep To Learn More
Still have questions? Our Regional Practice Leaders have the answers you need. Contact us today to learn more about the benefits of a group medical captive for your business.
Frequently Asked Questions About Group Captive Company Size
What is the minimum company size for a group captive?
Most group medical captives require a minimum of 25 employees. Below that threshold, the claims base is too small to price stop-loss coverage predictably, even within a pooled structure.
Can a company with fewer than 50 employees join a group captive?
Yes, provided it meets underwriting requirements. Roundstone’s captive accepts employers starting at 25 employees. The shared risk pool compensates for the smaller individual claims base.
What does an underwriter look for in a group captive applicant?
Underwriters evaluate claims history, workforce demographics, and leadership’s commitment to managing costs. A clean loss history and stable employee population are the strongest signals of a good fit.
Is a group captive a long-term commitment?
Policies run one year at a time, so there are no contractual handcuffs. That said, the financial benefits compound over time. Most employers start seeing meaningful results within two to three years of participation.
Can a company that's already self-funded join a group captive?
Yes, and the transition is typically straightforward. The primary change is moving stop-loss coverage into the captive structure. Employers can usually retain their existing TPA, PBM, and advisor relationships.
What happens if my company has a bad claims year in the captive?
Specific stop-loss coverage caps any single large claim. Above the captive layer, reinsurance absorbs the excess. Your maximum financial exposure is your contributed collateral — the program is not assessable beyond that.
How does collateral work when joining a group captive?
Members contribute collateral — typically less than 10% of the stop-loss premium — to help fund the captive’s risk pool. Any portion not needed to pay claims is returned or credited toward the next plan year.
Does industry type affect group captive eligibility?
Industry affects underwriting but doesn’t automatically disqualify an employer. What matters is claims history relative to industry peers. A company with better-than-average loss experience in a higher-risk industry can still be a strong candidate.
What is the difference between a group captive and a single-parent captive?
A single-parent captive is owned and operated by one company, requiring significant capital and administrative resources. A group captive pools multiple employers together, making captive economics accessible to companies that couldn’t sustain a solo structure.
