Guides
Treaty vs facultative reinsurance: how insurers share risk
Treaty reinsurance covers a whole book automatically; facultative covers one risk by negotiation. How each works, a worked split, and what it means for buyers.
Treaty reinsurance is a standing contract: the insurer (the ceding company) agrees in advance to pass a defined slice of a whole class of business to its reinsurers, and every policy that fits the terms is covered automatically. Facultative reinsurance is the opposite: the insurer shops one specific risk to reinsurers, who underwrite that risk individually and accept or decline it. Most of an insurer's reinsurance sits in treaties; facultative is the tool for the risk that is too big, too odd or too concentrated for the treaties to absorb.
You will never sign either contract, and the reinsurer owes you nothing directly. But treaty terms and facultative capacity decide how much limit your carrier can offer, which classes and locations it will write and sometimes how long a large placement takes. For the economics behind it, start with what is reinsurance, and why it affects your business premium.
Where the two sit in the structure
The company that issues your policy is the cedent. It remains fully liable to you whatever reinsurance it buys. If a reinsurer fails to pay, the insurer still owes you the claim; the risk of that failure is the insurer's, which is why regulators care about reinsurance collateral and reinsurer quality. The reinsurer's obligation runs to the insurer only, so a policyholder cannot normally sue the reinsurer directly. (Captive and fronted programs are the exception worth knowing about; see below.)
Reinsurance comes in two contract types, and the split is simply about how the risks are chosen.
- treaty reinsurance covers a defined portfolio, such as all of an insurer's commercial property written in the Southeast, for a contract year. The reinsurer agrees to accept the business without reviewing individual policies, and relies on the insurer's underwriting.
- facultative reinsurance covers one policy or one location. The insurer submits that risk, the reinsurer underwrites it as if it were a direct account, and a certificate documents the cover.
Treaty structures
Treaties divide into proportional and non-proportional forms.
| Treaty type | How it works | Typical use |
|---|---|---|
| Quota share | Reinsurer takes a fixed percentage of every policy in the class, and the same percentage of premiums and losses | New or volatile lines, capital relief, entering a class |
| Surplus share | Insurer keeps a set retention on each risk and cedes "lines" above it; the ceded share varies by policy size | Property written in a wide range of sizes |
| Per-risk excess of loss | Reinsurer pays the part of a single loss above an attachment point, up to a limit | Large single-building property and casualty losses |
| Catastrophe excess of loss | Reinsurer pays when losses from one event, summed across many policies, exceed an attachment point | Hurricane, earthquake, hail and wildfire accumulation |
| Aggregate or stop loss | Reinsurer pays when annual losses exceed a loss ratio or dollar amount | Volatile books; protection against a bad year |
In proportional treaties the reinsurer shares premiums and losses in the same ratio and pays the insurer a ceding commission to cover acquisition costs and overhead. In excess-of-loss treaties the reinsurer charges a premium for the layer, often expressed as a rate on line (premium divided by layer limit), and the insurer keeps everything below the attachment point. A catastrophe layer usually carries a reinstatement provision: after a loss uses the limit, the insurer can pay to restore it for the rest of the term.
Cat excess-of-loss pricing is the part of the treaty market that moves most. The Guy Carpenter U.S. Property Catastrophe Rate-on-Line Index fell about 16% through the 2026 renewal rounds and stood about 22% below its 2024 peak, according to Artemis's report on Guy Carpenter's July 2026 update. The index also reflects changes in exposure and structure, so it is not a pure price measure. How those costs reach your invoice is covered in how reinsurance pricing flows into business insurance premiums and the timing in The January 1 reinsurance renewals explained: the 2026 results.
How facultative works
Facultative reinsurance is placed by a reinsurance intermediary or by the insurer's own fac desk, and it follows a recognizable path.
- The insurer's underwriter finds a risk that exceeds treaty capacity, falls under a treaty exclusion or needs more limit than the net line allows.
- The insurer sends the reinsurer what it would send a primary underwriter: the statement of values, construction, occupancy, protection, loss runs, engineering reports and the proposed policy terms. See the statement of values: what property underwriters need for what that package looks like from the insured's side.
- The reinsurer quotes a share (proportional fac) or a layer (excess fac) and a price, or declines.
- Once bound, a fac certificate references the underlying policy and is usually written to follow its form and settlements.
A related hybrid, facultative obligatory (often "fac-oblig"), gives the insurer the option to cede risks within agreed guidelines while the reinsurer is bound to accept them. It sits between the two worlds: faster than case-by-case fac, narrower than a treaty.
Worked example (hypothetical)
Say a carrier agrees to write a $50 million property limit on a manufacturing plant. Its net retention on any one risk is $5 million, and its surplus treaty accepts up to four lines of $5 million, or $20 million. The remaining $25 million has to be bought as facultative reinsurance for this plant alone.
| Layer | Amount | Share of the $50 million |
|---|---|---|
| Carrier retention | $5 million | 10% |
| Surplus treaty | $20 million | 40% |
| Facultative | $25 million | 50% |
A $10 million fire loss would be split in those proportions: the carrier pays $1 million, the treaty reinsurers $4 million and the fac reinsurers $5 million. Premium is divided the same way, less ceding commissions. The insured sees one policy, one adjuster and one payment. The reinsurers' work happens behind it, and the fac reinsurers may want their own engineer's report and a timely loss notice on any large claim.
What this means when you buy
- Large property needs a longer runway. If your schedule includes a high-value location, the lead carrier may need fac support before it can quote its full line. Send a complete, accurate schedule early. Fac underwriters re-underwrite from scratch, and a values figure that looks stale or low costs time and sometimes limit.
- Treaty exclusions become policy limitations. A carrier whose cat treaty caps its Tier 1 coastal exposure cannot sell unlimited wind limit in those counties, however much it wants the account. When a carrier says "no capacity" for a class or location, a treaty or aggregate cap is often what it means. A wholesaler or a surplus lines market with different reinsurers may fill the gap.
- Claims on big losses get more eyes. Reinsurers on large losses typically have audit and notice rights, and the usual principle is that they follow the insurer's good-faith claim decisions within the contract. This rarely changes your result, but it can lengthen the file.
- Reinsurance is a solvency backstop, not a promise to you. If your insurer becomes insolvent, the reinsurance recoverables generally go to the receiver for the benefit of all claimants, not to you alone. State guaranty funds are the buyer's protection; see what happens when an insurer fails: guaranty funds and business policies.
- Captives and fronted programs change the chain. When a fronting insurer cedes nearly everything to your captive or a reinsurer, the policy holder's real counterparty is the reinsurer. Buyers sometimes negotiate a cut-through endorsement; the mechanics are in fronting arrangements and fronting carriers: how they work.
Regulation: why collateral matters
State credit-for-reinsurance rules decide whether an insurer can count a reinsurance recoverable as an asset or a reduction of liabilities. Under the NAIC Credit for Reinsurance Model Law (#785) and Model Regulation (#786), non-U.S. reinsurers historically had to post 100% collateral for U.S. risks. The NAIC's 2019 revisions, implementing the covered agreements with the EU and the UK, created a "Reciprocal Jurisdiction" category that eliminates collateral and local presence requirements for qualifying reinsurers. The NAIC reports that all 56 jurisdictions had implemented the revisions by October 2022 (NAIC brief). The practical effect is that a Bermuda, London or European reinsurer can compete for U.S. treaties without tying up as much capital in U.S. trust accounts. For who those reinsurers are, see the world's largest reinsurers: 2026 rankings and what they mean.
Key takeaways
- Treaty reinsurance covers a defined portfolio automatically; facultative reinsurance covers one risk after the reinsurer underwrites it.
- Proportional treaties share premium and loss at a set ratio; excess-of-loss treaties pay above an attachment point, and catastrophe layers are the most price-sensitive.
- Large or unusual property risks often need fac support, so complete values and engineering data speed the placement.
- You have no direct claim against your insurer's reinsurer, but treaty limits and fac capacity shape how much cover your carrier can offer.
- Credit-for-reinsurance rules, including the 2019 NAIC revisions, determine how much collateral reinsurers must post in the United States.