Definition:Per-occurrence reinsurance
🔁 Per-occurrence reinsurance is a form of reinsurance in which the reinsurer's liability is triggered by the total loss from a single covered occurrence exceeding a specified retention (also called an attachment point), with the reinsurer then paying up to a defined limit for that event. This structure is the backbone of excess of loss treaty programs, allowing ceding companies to protect their balance sheets against the outsized financial impact of large individual losses or catastrophic events. The approach contrasts with aggregate reinsurance, which responds to cumulative losses over a period, and with proportional reinsurance, which shares every loss from the first dollar according to a fixed percentage.
⚙️ A typical per-occurrence excess of loss treaty might read "$10 million excess of $5 million per occurrence," meaning the cedent retains the first $5 million of each occurrence loss, and the reinsurer covers up to $10 million above that threshold. The definition of "occurrence" in the reinsurance contract is paramount — and often differs subtly from the underlying insurance policy language — since it determines whether related losses are grouped together or treated independently. For catastrophe reinsurance, an occurrence typically encompasses all losses from a single natural disaster within a defined time window (often 72 to 168 hours for windstorm events). Pricing relies on catastrophe models, historical loss data, and exposure analysis, with terms negotiated in major reinsurance markets including London, Bermuda, Zurich, and Singapore. Regulatory frameworks such as Solvency II grant capital relief to cedents for risk transfer achieved through qualifying per-occurrence treaties, provided the arrangement meets specific standards around genuine risk transfer and documentation.
💡 Per-occurrence reinsurance enables insurers to write business that would otherwise concentrate too much risk on a single event — a hurricane, an industrial explosion, or a mass tort — relative to their surplus. Without it, many primary insurers would be unable to offer the per occurrence limits that commercial and industrial policyholders require. The structure also plays a critical role in stabilizing industry results after major catastrophe losses: when a devastating earthquake or windstorm strikes, per-occurrence reinsurance treaties spread the financial burden across a global pool of reinsurers and ILS investors. The clarity of the per-occurrence trigger — one event, one recovery — makes it the most transparent and widely understood reinsurance structure, serving as the default building block of most non-proportional reinsurance programs worldwide.
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