A reinsurance attachment point is the dollar amount of losses a primary insurer must absorb on its own before its reinsurer begins paying. It functions like a deductible between two insurance companies: losses below the line stay with the primary insurer, and losses above it shift to the reinsurer up to an agreed ceiling. Where that line sits drives how much the reinsurance costs, how much capital the insurer has to hold against retained risk, and how rating agencies view the company’s financial strength.
Where the Layer Starts and Where It Ends
The attachment point is the retention limit written into every excess-of-loss reinsurance contract. Below it, the primary insurer is on its own. Above it, the reinsurer responds.
Every reinsurance layer also has a ceiling, sometimes called the exhaustion point or detachment point, that caps the reinsurer’s exposure. A “$3 million excess of $2 million” layer means the attachment point is $2 million and the reinsurer covers up to $3 million above it, with total exposure ending at $5 million. Losses beyond $5 million either fall back on the insurer or get picked up by a higher layer. The width between attachment and exhaustion defines the layer’s size, and in turn its price.
How Coverage Triggers in a Claim
During a loss event, the primary insurer pays 100 percent of claims until the running total reaches the attachment point. Once losses cross it, the reinsurer pays the excess, continuing until the layer’s limit is used up.
A worked example makes the math clearer. Suppose an insurer holds a treaty with a $1 million attachment point and a $5 million limit above it. A hurricane generates $4 million in total claims. The insurer pays the first $1 million, and the reinsurer covers the remaining $3 million. If the same storm produced $7 million in losses, the reinsurer would pay its full $5 million, and the insurer would owe the first $1 million plus the $1 million above the reinsurer’s ceiling. Stacking multiple layers at staggered attachment points lets insurers build a tower of protection, with each successive reinsurer picking up a higher, less likely slice of loss.
Contract Structures That Change How Losses Count
Not every attachment point works the same way. The contract structure determines how losses accumulate toward the threshold, and picking the wrong structure can leave an insurer exposed in ways it didn’t anticipate.
Per Risk
A per risk attachment point applies to each individual insured risk separately. A single large property fire has to breach the retention on its own before the reinsurer pays. Smaller claims on other policies don’t count toward the threshold. This structure protects against one-off catastrophic losses on a single account, such as a warehouse explosion or a massive liability verdict, while keeping routine claims entirely with the primary insurer.
Per Occurrence
Per occurrence treaties aggregate all losses from a single event. A hurricane that damages thousands of homes generates thousands of individual claims, but they all roll up into one total. If that combined total exceeds the attachment point, the reinsurer responds. This is the standard structure for catastrophe reinsurance, where the real danger isn’t any single claim but the volume hitting at once.
An important wrinkle in per occurrence contracts is the hours clause, which defines the time window for grouping claims into one occurrence. The window varies by peril. Tornado losses might need to fall within a 24-hour window. Windstorm losses often get a 72-hour window, while flood losses may use a 168-hour window in the United States. Any claims outside that window are treated as a separate occurrence with its own attachment point. Longer windows benefit the insurer because more claims aggregate together, making it easier to breach the attachment point; reinsurers push for shorter windows to limit their exposure.
Aggregate Excess
Aggregate treaties track the insurer’s total losses across all risks and events over a set period, usually a calendar year. The attachment point triggers only after cumulative annual losses exceed the threshold. This is the backstop for years when losses pile up from many directions without any single event being catastrophic. A book of business can be perfectly manageable on paper and still run into bad luck across dozens of unrelated claims, and the aggregate layer absorbs the overrun.
Clash Cover
Clash cover addresses the scenario where one event triggers claims across multiple, seemingly unrelated policies. A corporate bankruptcy, for example, might simultaneously hit an insurer’s directors-and-officers book, its professional liability book, and its surety bond portfolio. The clash attachment point triggers when losses from these separate policy types, all traceable to the same underlying event, exceed the retention in combination. Three conditions typically must be met: losses must arise from multiple policies, all damage must trace to the same event, and the event must occur within a defined timeframe.
How Loss Adjustment Expenses Interact With the Threshold
Claims cost more than the face value of the loss. Legal defense, expert witnesses, investigation, and administrative costs (collectively called allocated loss adjustment expenses, or ALAE) add up fast, and how they’re treated in relation to the attachment point can swing the economics of a treaty significantly. Two approaches dominate the market.
Under the “pro rata with loss” method, ALAE within the reinsured layer gets allocated in proportion to the losses themselves. If 60 percent of the loss falls within the treaty layer, 60 percent of the ALAE does too. Under the “included in loss” method (also called “part-of-loss” or “add-on”), ALAE gets stacked on top of the indemnity amount, and the attachment point applies to the combined total. That second approach pushes losses above the attachment point faster, which is good for the cedant and worse for the reinsurer. Treaty language spells out which method applies, and sophisticated buyers negotiate this carefully because the financial difference between the two methods can be substantial on large, litigation-heavy claims.
How Insurers Choose Where to Set It
Setting the attachment point is one of the most consequential decisions in a reinsurance program. Set it too low and the insurer pays steep premiums for coverage it probably won’t need. Set it too high and a bad year could threaten its ability to pay policyholders.
Capital and Surplus
The starting point is how much loss the company can absorb without jeopardizing its financial stability. Insurers with deep surplus and strong liquidity can afford higher attachment points, retaining more risk and pocketing the premium savings. Smaller or thinly capitalized insurers tend to set lower attachment points because they can’t afford the volatility of large retained losses.
Risk-Based Capital Requirements
State insurance regulators use Risk-Based Capital (RBC) standards, developed through the NAIC’s model act framework, to set minimum capital floors tied to each insurer’s risk profile. Unlike older fixed-capital requirements that applied the same minimum to every company regardless of size or risk, RBC formulas scale with the insurer’s actual exposure. An insurer writing heavy catastrophe-exposed business needs more capital than one focused on low-severity lines. Where the attachment point sits directly affects the net risk the insurer retains, which in turn influences the capital charge under the RBC calculation. Setting it too high without adequate surplus behind it can push an insurer toward a regulatory action level.
Rating Agency Pressure
AM Best and other rating agencies evaluate the quality and appropriateness of an insurer’s reinsurance program as part of their financial strength assessments. AM Best’s capital model applies a surcharge when an insurer is excessively dependent on unaffiliated reinsurers, with escalating risk charges when ceded leverage reaches 5, 7, or 10 times surplus. At the same time, AM Best reviews whether reinsurance contracts genuinely transfer risk. Contracts loaded with provisions that limit the reinsurer’s actual exposure (loss ratio caps, sliding-scale commissions, cancellation triggers) may be treated as having no meaningful risk transfer, which can hurt the insurer’s balance sheet strength assessment. The attachment point needs to land in a zone where the insurer retains enough risk to avoid a dependence surcharge but transfers enough to maintain adequate capital ratios.
Market Cycle
The reinsurance market swings between hard and soft cycles, and the cycle affects what attachment points are realistically available. During a hard market, reinsurers push attachment points higher because they want to avoid frequent, attritional losses. The 2023 renewal season was a textbook example, with reinsurers demanding significantly elevated retentions after several years of heavy catastrophe losses. By mid-2025, the market had shifted, with increased supply and competition bringing more flexibility, particularly for insurers with clean loss records. That softening trend was expected to continue into 2026 renewals, though reinsurers still differentiate sharply based on an insurer’s track record.
How the Attachment Point Drives Premium
The relationship between the attachment point and the reinsurance premium is inverse, and it is steep. A low attachment point means the reinsurer is more likely to pay claims, so it charges more. A high attachment point means the reinsurer rarely gets involved, so the premium drops significantly. This is the single biggest lever an insurer can pull to manage reinsurance costs.
The economics work the same way a homeowner’s insurance deductible does, just with more zeros. Choosing a $500,000 attachment point instead of $1 million dramatically increases the frequency with which the reinsurer expects to pay. That increased expected loss gets priced directly into the premium, along with a risk load and the reinsurer’s margin.
Burning Cost
One of the most common pricing methods is experience rating, often called the burning cost approach. The reinsurer compiles the insurer’s historical loss data over as many years as are available (ten is typical), adjusts each year’s losses for inflation so they reflect current cost levels, applies development factors to account for claims that haven’t fully settled, and then calculates how much of those adjusted losses would have pierced the proposed attachment point. The average annual cost within the layer, expressed as a percentage of the insurer’s premium volume, becomes the starting point for the reinsurance rate. An insurer with a history of large losses breaching the proposed attachment point will pay a higher burning cost rate than one with a clean record at the same retention level.
What Happens to the Limit After a Loss
When a reinsurer pays a loss, the available limit in that layer shrinks by the amount paid. If a $5 million layer pays a $3 million claim, only $2 million of protection remains. A second event could exhaust the layer entirely, leaving the insurer exposed for the rest of the contract period.
Reinstatement clauses address this by restoring the limit after a loss, but they come at a price. The reinstatement premium is typically calculated pro rata based on how much of the limit was used. If an insurer has a $10 million layer with a $2 million annual premium and a reinstatement provision at 110 percent, and a loss consumes $4.5 million of the layer, the reinstatement premium would be approximately $990,000 (the annual premium multiplied by 110 percent, multiplied by the fraction of the limit used). The number of reinstatements allowed, the cost multiplier, and whether reinstatement is automatic or requires mutual agreement are all negotiated terms. Catastrophe treaties almost always include reinstatement provisions because a single hurricane season can produce multiple qualifying events.
Attachment Points Beyond Traditional Reinsurance
The same concept appears in catastrophe bonds, where investors rather than a traditional reinsurer provide the loss-absorbing capital. A cat bond might cover “$100 million excess of $825 million,” meaning the sponsor’s losses must exceed $825 million before the bond starts paying, with the investors’ principal at risk up to the $100 million limit. The trigger mechanism differs: indemnity triggers follow the sponsor’s actual losses like traditional reinsurance, while industry loss and parametric triggers tie payment to industry-wide loss estimates or to physical event characteristics such as earthquake magnitude or hurricane wind speed. Parametric and industry-loss structures pay out far faster but introduce basis risk, because the bond might pay when the sponsor’s actual losses are low, or fail to pay when they are high.
A Note on Regulation
Reinsurance operates with notably lighter regulatory oversight than primary insurance. Because both parties to a reinsurance contract are sophisticated commercial entities, most states impose no requirements for filing or approval of reinsurance contract terms, including attachment points, and regulators don’t typically review the rates negotiated between a cedant and its reinsurer. The regulatory focus falls instead on whether the insurer can take financial statement credit for the reinsurance it purchases under the NAIC’s Credit for Reinsurance Model Law. That means an insurer’s choice of reinsurer, and by extension its entire program structure, is constrained less by what attachment point it picks and more by whether the arrangement will receive regulatory credit on the balance sheet.