What is reinsurance, and why it affects your business premium

Reinsurance is insurance that insurance companies buy. Your carrier pays a reinsurer a share of premium, and the reinsurer agrees to pay a share of certain losses. It matters to a business buyer because reinsurance determines how much property and casualty risk your insurer can afford to write, at what price, and with what limits, even though you never see the contract.

Your policy is with the insurer. A reinsurer owes you nothing directly, and a reinsurer's failure to pay does not release your insurer from paying your claim. The link is economic. When reinsurance gets cheaper or scarcer, it shows up at your renewal as rate, appetite, sublimits and capacity.

Why insurers buy it

An insurer has a finite amount of capital, which regulators measure as statutory surplus. Each policy written commits some of it. Reinsurance does four jobs:

• Caps a single bad loss. A carrier that writes $10 million property limits on one building can reinsure the top of it, so one fire does not threaten its balance sheet.
• Protects against accumulation. A hurricane or hail event hits hundreds of policies at once. Catastrophe reinsurance pays when total losses from one event cross a threshold.
• Smooths results. Reinsurance turns a lumpy year into a steadier one, which is what rating agencies and investors want to see.
• Creates capacity. Because part of each risk is passed on, the same capital supports more premium. A small regional carrier can write a large account on that basis.

Reinsurance is also how a carrier enters a class where it lacks expertise. Reinsurers bring data and underwriting views on lines like cyber or excess and surplus property, and they price it from experience across many clients.

The two main structures

Treaty reinsurance covers a whole book of business under one contract, automatically. The insurer does not ask the reinsurer about each policy. Facultative reinsurance is negotiated one risk at a time and is used for a large or unusual account. The details are in treaty vs facultative reinsurance: how insurers share risk.

Treaties are also split by how they share loss:

The insurer's retention in a non-proportional program is the amount it pays before the reinsurer pays. A carrier that raises its retention is taking more of the loss itself. Those choices flow into underwriting rules: how many policies it will write in a hurricane zone, how much it will offer on one building, and whether it adds a wind sublimit.

How reinsurance is priced and traded

Excess of loss cover is priced as a rate on line: premium divided by the limit. A layer that costs $5 million for $50 million of limit has a 10% rate on line. Brokers publish indices of how those rates move at each renewal, and the January 1 and June 1 and July 1 renewals set the tone for the year. See The January 1 reinsurance renewals explained: the 2026 results for the 2026 results.

Reinsurers price with catastrophe models plus their own view of how models miss: secondary perils, inflation in repair costs, litigation trends. They also look at the carrier's data quality and how exposures are coded. A carrier that cannot show roof age, construction and sprinkler status for its commercial buildings pays more for the same cover, and passes some of that on.

Capital comes from traditional reinsurers, from Lloyd's syndicates (How Lloyd's of London works: syndicates, brokers and what it means for you), from the Bermuda market (The Bermuda insurance and reinsurance market) and from investors through Catastrophe bonds and ILS: how they work and who they affect and other insurance-linked securities. The largest players are listed in the world's largest reinsurers: 2026 rankings and what they mean.

How it reaches your renewal

You will rarely hear the word reinsurance from your broker, but you will feel it:

• Property rates and terms. When catastrophe reinsurance is expensive, carriers raise commercial property rates in exposed states, shrink their limits, and push wind and hail deductibles up. named storm deductibles: how percentage wind deductibles work are the visible example. When reinsurance is cheap and plentiful, rate increases flatten and capacity returns.
• Appetite for a class. A carrier whose treaty excludes or restricts a class, such as habitational frame buildings or roofers, must follow it. Appetite follows the treaty.
• Limits per policy. Net line limits at an insurer are set by its reinsurance. If you need more than the carrier's line, the broker splits the layer between carriers or goes to a wholesaler.
• Casualty and umbrella pricing. Casualty reinsurers worry about social inflation (growth in jury awards and settlement costs), and their terms feed through to excess liability. See umbrella vs excess liability.
• Cyber. Reinsurers watch systemic events, and their wording on widespread outages and war is reflected in primary policy exclusions.

A hypothetical illustration: say a regional carrier writes $400 million of commercial property in the Gulf Coast states and buys catastrophe cover that starts paying above a $60 million loss. At the next renewal reinsurers raise the price 25% and move the attachment up. The carrier either absorbs the cost, raises rates 8% to 12% on coastal accounts, or cuts back on new business near the water. You, as a buyer there, see one of those three.

What reinsurance is not

• It is not a guarantee your insurer pays. Your protection is the insurer's own financial strength, state regulation and, if it fails, the guaranty fund.
• It is not the same as fronting. A fronting carrier issues policies and cedes most of the risk to a captive or another reinsurer, which is covered in fronting arrangements and fronting carriers: how they work.
• Reinsurers do not deal with policyholders. Claim disputes are with your insurer. A carrier may have reinsurer approval rights on large settlements, which can slow a major claim.

What to ask your broker

1. Is the carrier's property capacity in my state changing, and is that tied to its reinsurance?
2. Are my building values and occupancy information in the form carriers need for modeling?
3. Is the quote reliant on a facultative placement, and what happens if that falls through before binding?
4. If rates on catastrophe reinsurance are falling, why is mine not?
5. Would a higher deductible or a different layer structure be priced better with this carrier?

Question 4 has a straightforward answer: reinsurance is one input, alongside your loss history, claims inflation, the rate the carrier needs on that class, and the carrier's own retained losses. how reinsurance pricing flows into business insurance premiums walks through how those pieces combine.

Key takeaways

• Reinsurance is insurance bought by insurers. It gives them capacity and protection from big losses, but your contract is only with your insurer.
• Treaty cover applies to a whole book; facultative cover applies to one risk. Cover is proportional (shared premium and loss) or non-proportional (above a retention).
• Reinsurance pricing and terms set how much property and casualty capacity carriers have, which is why catastrophe-exposed property reacts most.
• The 2026 reinsurance market has been softening, but primary rates depend on much more than reinsurance cost.