The Four Pillars of Health Insurance Funding: TPA, Network, PBM, and Stop Loss Explained

Most executives evaluating their organization's health plan think in terms of a single choice: which carrier to use. That framing obscures what is actually being purchased. Every health plan, regardless of carrier or funding structure, is assembled from the same four underlying components. A fully insured plan bundles all four together and sells them to the organization as one package. A self-funded plan unbundles them and lets the organization purchase, and manage, each one directly. Understanding these four pillars is the foundation for every other decision about how a health plan is funded, and it is the starting point for any organization that wants to actively manage its benefits costs rather than simply absorb whatever the renewal brings.

Why the Funding Question Matters More Than the Carrier Question

Health insurance is, at its core, a financing mechanism. When an employee receives care, someone has to pay for it. The question every organization is actually answering, whether it realizes it or not, is how that care gets funded and how much visibility the organization has into what it is actually paying for.

In a fully insured arrangement, the carrier absorbs this question entirely. The organization pays a fixed premium, and the carrier is responsible for paying claims, managing the network, administering the plan, and absorbing the risk if claims run high. The organization has minimal visibility into what is actually happening inside that premium dollar. In a self-funded or partially self-funded arrangement, the organization takes on more of that responsibility directly, and in exchange, gains far more visibility into where the money is actually going.

Neither approach is inherently better. The right structure depends on the organization's size, risk tolerance, and appetite for actively managing the plan rather than treating it as a fixed cost. But every point along that spectrum, from fully insured to fully self-funded, is built from the same four components.

The Third-Party Administrator (TPA)

The TPA is the administrative engine of the plan. It processes claims, manages enrollment, handles day-to-day plan administration, and serves as the operational backbone connecting the employer, the employees, and the other pillars of the plan. In a fully insured arrangement, the carrier typically performs this function internally. In a self-funded arrangement, the organization selects a TPA directly, which opens the door to choosing an administrator based on service quality and reporting capability rather than accepting whichever administration comes bundled with the carrier.

The Network

The network determines which providers, hospitals, and facilities employees can access, and at what negotiated rate. Network access is one of the most visible components of a health plan to employees, since it directly affects which doctors they can see and how much a given visit costs. Networks vary significantly in size, negotiated discount depth, and geographic coverage, and the choice of network has a direct, material effect on both the cost of the plan and the experience employees have using it.

The Pharmacy Benefits Manager (PBM)

The PBM manages the pharmacy side of the plan: negotiating drug pricing, processing prescription claims, and determining which medications are covered and at what cost to the employee. Pharmacy costs have become one of the fastest-growing components of overall health plan spend, which makes the PBM relationship a increasingly significant factor in total plan cost. As with the TPA, a self-funded structure allows an organization to select its PBM independently, rather than accepting whatever pharmacy arrangement is bundled into a fully insured product.

Stop Loss Coverage

Stop loss is the insurance component that protects an organization from catastrophic claims when it is funding claims itself, whether partially or fully. If a single employee generates an unusually large claim, stop loss coverage caps the organization's exposure at a defined threshold, with the stop loss carrier responsible for costs above that point. This is what makes self-funding a viable strategy for organizations that are not large enough to absorb a catastrophic claim entirely on their own balance sheet. Without stop loss, a self-funded organization would be exposed to unlimited claims risk, which is why this component exists specifically as a backstop rather than a primary funding mechanism.

How These Four Pillars Combine Into a Funding Strategy

The difference between a fully insured plan, a level-funded plan, a partially self-funded plan, and a fully self-funded plan is not a difference in what is being purchased. It is a difference in how these four pillars are bundled, and how much of the underlying risk and administrative responsibility the organization is taking on directly.

Fully insured. The carrier bundles all four pillars into a single product and absorbs the underlying risk. The organization pays a predictable premium and has limited visibility into the claims data driving that premium. This structure works well for organizations that want predictability and minimal administrative involvement, though it typically comes at a premium cost that reflects the carrier absorbing the full risk.

Level funded. The plan is structured to feel similar to fully insured, with a flat monthly cost, but the organization is actually funding its own claims within a pre-set budget, supported by stop loss coverage. The pillars are often prepackaged together by the carrier or a partner, but the underlying cost is driven specifically by that organization's own claims experience rather than pooled across a broader book of business.

Partially self-funded. The organization pays claims directly out of its own funds, up to a stop loss threshold that caps catastrophic exposure. This structure typically requires the organization to select and coordinate its own TPA, network, and PBM relationships, either directly or through a consultant, rather than accepting a single bundled product.

Fully self-funded. The organization retains the most risk and the most control, funding claims directly with stop loss coverage sitting above a higher retention threshold. This structure provides the greatest visibility into claims data and the greatest flexibility to customize plan design, network access, and pharmacy management, but it also requires the most active management and the greatest tolerance for claims volatility.

Why This Distinction Matters for Cost Management

The practical significance of these four pillars becomes clear once an organization starts trying to manage its health plan costs actively rather than simply absorbing each year's renewal. An organization in a fully insured arrangement has very limited ability to influence its own costs, because it has very limited visibility into what is driving them. The carrier sees the claims data. The organization sees a premium.

An organization that has unbundled these pillars, even partially, gains direct visibility into what is actually happening: which claims are occurring, which providers are being used, where pharmacy costs are concentrated, and whether utilization patterns suggest an opportunity to steer employees toward higher-value care. That visibility is what allows an organization to actually manage the two levers that determine health plan cost over time: the frequency and severity of the claims being paid. Without visibility into claims data, an organization is left reacting to whatever number the renewal produces, with little ability to understand or influence why that number moved.

This does not mean every organization should pursue self-funding. Smaller organizations, or those with limited tolerance for claims volatility, are often better served by the predictability of a fully insured or level-funded arrangement. But every organization benefits from understanding what it is actually purchasing across these four components, because that understanding is what makes an informed funding decision possible in the first place, rather than a decision made by default because it is what has always been in place.

What to Ask When Evaluating Your Current Structure

• Do you know how your current plan is funded across these four components, or only what the total premium or monthly cost is?
• If your plan is level funded or self-funded, do you have direct visibility into claims data, or does that information stay with the carrier or TPA?
• Has your funding strategy been reevaluated as your organization has grown, or is it the same structure that was put in place years ago?
• Is your organization's tolerance for claims volatility being weighed deliberately against the potential savings of a less bundled funding structure, or has that tradeoff never been formally assessed?

The Bottom Line

Every health plan is built from the same four components: a TPA, a network, a PBM, and stop loss coverage. The difference between funding strategies is not what is being purchased, but how those pillars are bundled and how much visibility and risk the organization takes on directly. Poms & Associates works with organizations to evaluate their health plan funding strategy with the same discipline behind every program we build from a risk assessment first, because a benefits strategy built on genuine visibility into cost drivers serves an organization far better than one accepted by default at each renewal.

If your organization has never evaluated its health plan against these four components directly, talk to a Poms & Associates advisor before your next renewal cycle.

Frequently Asked Questions

What are the four pillars of health insurance funding? Every health plan is built from a third-party administrator (TPA), a provider network, a pharmacy benefits manager (PBM), and stop loss coverage. Fully insured plans bundle all four together through a single carrier, while self-funded plans allow an organization to select and manage each component more directly.

What is the difference between fully insured and self-funded health insurance? In a fully insured plan, the carrier absorbs the underlying claims risk and bundles administration, network access, and pharmacy management into a single premium. In a self-funded plan, the organization pays claims directly, gains more visibility into claims data, and typically uses stop loss coverage to cap exposure to catastrophic claims.

What does stop loss coverage actually do? Stop loss coverage protects a self-funded or partially self-funded organization from catastrophic claims by capping the organization's exposure at a defined threshold. Claims costs above that threshold are covered by the stop loss carrier, which is what makes self-funding a viable strategy for organizations that could not otherwise absorb a single large claim.

Is self-funding a good fit for every organization? No. Self-funding shifts more risk and administrative responsibility onto the organization in exchange for greater visibility and control over costs. Organizations with limited tolerance for claims volatility, or that are not large enough to absorb the risk even with stop loss coverage, are often better served by a fully insured or level-funded structure.

Why does visibility into claims data matter for managing health plan costs? Managing health plan costs over time depends on understanding and influencing the frequency and severity of the claims being paid. In a fully insured plan, that data stays largely with the carrier. A funding structure that provides direct access to claims data allows an organization to actually identify cost drivers and make informed decisions, rather than simply reacting to each year's renewal number.