The mental model

Treaty reinsurance is the standing arrangement under which a reinsurer accepts a defined portion of a cedant's underwriting results. The treaty has a term (usually one year), is renewed on a defined cycle, and is supported by ongoing reporting. The renewal cycle is the annual moment when the cedant secures capacity for the year ahead, and the reporting cycle is what proves the treaty was earned during the year that just passed.

For a primary carrier, treaty reinsurance is mission-critical. The treaty determines how much net retained risk the carrier holds, how its book responds to severity, and how its capital is leveraged. Treaty terms also flow into the carrier's day-to-day underwriting because front-line underwriters need to know what the treaty covers, what's excluded, and where the attachment points sit. The renewal cycle is where the strategic conversation between cedant and reinsurer happens. Multi-year reinsurer relationships are valued, but the renewal is also where reinsurers can re-price, restructure, or withdraw. After the renewal, the cedant's reporting obligations begin: monthly or quarterly bordereaux, premium and loss reports, and (for proportional treaties) ceded premium and ceded losses on a per-risk or aggregate basis.

The 1/1 cycle

Most treaty reinsurance globally renews January 1. The build-up to 1/1 follows a defined sequence.

Q3 (July - September): preparation

• The cedant's reinsurance broker meets with the cedant to discuss strategy: structure changes, target pricing, capacity needs.
• The broker prepares the renewal pack: cedant data, treaty wordings, exposure summaries, loss summaries.
• The cedant's actuarial team produces updated loss triangles, ultimate-loss estimates, and rate adequacy analyses.
• Underwriting and operations contribute current portfolio metrics and forward-year forecasts.

Late Q3 - early Q4 (September - October): marketing

• The broker takes the renewal pack to the reinsurer market, formally or through a series of firm individual meetings (the Monte Carlo Rendez-Vous in early September is a major informal market sounding).
• Reinsurers indicate interest, request additional data, and provide preliminary pricing or coverage feedback.
• Cedant management (the chief reinsurance officer or equivalent) attends key reinsurer meetings to set the relationship tone.

Q4 (October - December): firming and binding

• Reinsurers provide formal quotes against the broker's slip.
• The broker negotiates terms, adjusts the slip, and finalizes the layer placements.
• Reinsurers signal lead pricing; the slip walks through following markets to assemble full subscription.
• Final binding occurs in December, with the slip signed by all participating reinsurers before December 31.
• Treaty wordings are finalized and any negotiated language refined in the closing weeks.

Why January 1

The convention reflects calendar-year accounting alignment, the European insurance market's January-December year, and the operational reality that a single mass-renewal date concentrates reinsurer underwriting capacity. Mid-year renewals exist for specific markets (Florida hurricane, Asia property cat) but the bulk of the global reinsurance market converges on 1/1.

The broker pack

The broker pack is the standardized data package the cedant's reinsurance broker produces for each treaty being renewed.

Standard contents

• Cover letter / executive summary. Brief overview of the cedant's year, key metrics, strategic positioning.
• Treaty wording or slip. The proposed terms for the renewal year, including all key conditions.
• Loss triangles. Multi-valuation incurred and paid loss development for the underlying book of business.
• Premium history. Gross written premium, ceded premium, retained premium by line and segment over a multi-year history.
• Cession history. Treaty-level results: ceded premium, ceded losses, ceded loss ratio, ceding commission earned by the cedant.
• Exposure data. For property and catastrophe treaties, location-level exposure data feeding catastrophe modeling.
• Loss listing. Significant individual claims, with descriptive narratives where helpful.
• Modeling output. Catastrophe modeling output (RMS, AIR, Karen Clark) with the reinsurer's preferred view, including AAL, OEP, AEP curves.
• Forward-year forecast. Cedant's expectations for the renewal year: premium growth, exposure changes, retention strategy.

Treaty-specific additions

Different treaty types have additional standard sections:

• Property cat XL. AAL, modeled cat curves, recent cat experience, exposure changes.
• Casualty XL. Per-claim severity distribution, large-loss listing, litigation and venue analysis.
• Quota share. Underlying loss ratio history, expense ratio, cession terms negotiation.

Quality and consistency

The broker pack is competitive material; cedants invest meaningfully in producing high-quality packs because the pack quality affects pricing. A well-organized pack with clear narrative around loss development reduces reinsurer perceived uncertainty and supports better terms.

Treaty types in renewal

Different treaty types follow different renewal mechanics. Chapter 26 covered the structures; here is the renewal angle.

Property catastrophe XL

The most market-sensitive treaty type. Pricing is driven by modeled output, recent cat experience, and reinsurer market conditions. Capacity can shift dramatically between renewals; price changes of ±30% from one year to the next are normal in volatile years. The 2023-2024 renewals were among the hardest in 20 years for property cat treaty, with substantial price increases and tighter terms.

Per-risk excess

Less market-sensitive than cat XL but still cycle-driven. Severity-driven, with claim trend and venue concerns affecting reinsurer pricing.

Casualty quota share

Driven by the underlying loss ratio of the cedant's book and the ceding commission negotiation. The ceding commission is the cession structure's main negotiating variable.

Aggregate stop-loss

Niche product; pricing is heavily volatility-driven and depends on the cedant's stable-loss-ratio history.

Multi-year structures

Some treaties are written on multi-year terms with renewal options. Common in casualty, less common in property cat. The multi-year structure protects against single-year market disruption but locks in pricing assumptions.

Modeling and pricing

For property catastrophe treaties (and increasingly for severe convective storm and wildfire layers), the renewal process is heavily model-driven.

The model output

• AAL (Annual Average Loss). The expected loss for the layer per year.
• OEP (Occurrence Exceedance Probability). The probability of any single event exceeding a defined size.
• AEP (Aggregate Exceedance Probability). The probability of total annual losses exceeding a defined size.
• Per-event PML. The probable maximum loss for specific scenarios (1-in-100 hurricane, 1-in-250 earthquake).

Reinsurer view of model output

Each reinsurer applies its own adjustments to the cedant-supplied model output. Reinsurers may "view-load" the AAL upward to reflect concerns about climate change, exposure data quality, or model uncertainty. The view-loaded AAL drives the reinsurer's pricing.

Pricing components

• AAL (the expected loss).
• Loaded AAL (with reinsurer adjustments).
• Capital cost on the layer (reflecting the risk of the layer to the reinsurer's balance sheet).
• Expense and profit loads.
• Brokerage commission.

The result: rate-on-line

The price for a layer is typically expressed as rate-on-line (premium ÷ layer limit). A property cat layer with a $100M limit and a 5% rate-on-line costs $5M in premium. Rate-on-line is the comparison metric across reinsurers and across renewal years.

Cedant reporting cycle

After the treaty is bound, the cedant has reporting obligations through the year. The reporting cycle is the operational backbone of treaty management.

Quarterly reporting (most common)

• Premium bordereau. Per-risk or aggregate premium ceded during the quarter.
• Loss bordereau. Per-risk or aggregate losses ceded during the quarter (paid and outstanding).
• Treaty performance summary. Cumulative ceded premium and losses, with calculated ceded loss ratio.
• Significant claims notifications. Detailed reporting on individual claims that meet a defined materiality threshold.
• Reinstatement premium calculations. For excess treaties with reinstatement provisions, calculation of any reinstatement premium owed.

Annual reporting

• Statement of account. Final reconciliation of ceded premium and ceded losses for the treaty year.
• Treaty profit commission calculation. For treaties with profit commissions, the calculation of any commission owed back to the cedant.
• Stewardship report. Comprehensive review of the treaty year, including business mix changes and forward-year planning.

Event-driven reporting

• Cat event notifications. Within hours of a major catastrophe event, cedants notify reinsurers with initial loss estimates and updated estimates as data develops.
• Large loss notifications. Individual claims exceeding defined thresholds, with regular updates as the claim develops.
• Coverage disputes. Material coverage questions or disputes that could affect the treaty's response.

Where treaty performance is measured

The treaty has a financial result that the reinsurer tracks closely and that the cedant uses for its own portfolio management.

Cedant view

• Net cession economics. Premium ceded, losses ceded, ceding commission earned, net cost to cedant.
• Capital relief. The reinsurance reduction in required capital, calculated under the cedant's regulatory framework.
• Volatility reduction. The reinsurance impact on the cedant's net loss ratio volatility.
• Coverage adequacy. Whether the treaty actually responded as intended for actual events that occurred.

Reinsurer view

• Underwriting result. Premium received vs losses paid plus reserves carried, plus commissions and expenses.
• Combined ratio. Total expense plus loss ratio for the treaty.
• Multi-year performance. The treaty's performance over multiple years, since single-year results in cat-exposed treaties are dominated by event volatility.
• Capital efficiency. Return on capital deployed against the treaty.

The renewal feedback loop

Treaty performance from prior years feeds directly into the next renewal. Sustained adverse results trigger price increases or coverage tightening. Sustained favorable results support price decreases or capacity expansion. The performance-renewal feedback loop is the discipline that keeps the treaty market priced approximately to long-run cost.

Mid-year renewals and off-cycle treaties

While 1/1 dominates, several other renewal dates matter.

April 1

Major renewal date for Japan reinsurance. Aligned with the Japanese fiscal year. Concentrated focus on Japan earthquake, Japan typhoon, and Asian regional cat capacity.

June 1

The Florida market renewal date. Florida hurricane reinsurance is concentrated in the May-June period. Texas, Caribbean, and Gulf hurricane treaties also frequently renew in this window.

July 1

Australian and New Zealand reinsurance renewals. Aligned with the Australian fiscal year. Concentrated focus on bushfire, severe convective storm, and earthquake exposure in the region.

October 1

Some U.S. casualty programs and several specific specialty treaties. Less volume than the major renewal dates but a notable secondary date.

Off-cycle and continuous renewal

Some treaties are continuously renewed or have rolling terms; multi-year treaties may renew on portions of the program at different times. Aviation, marine, and certain political risk treaties often have non-standard renewal cycles.

Where IDP earns its keep

The reinsurance reporting cycle generates a large volume of structured documents, all of which need to flow accurately between the cedant and the reinsurer. Premium bordereaux, loss bordereaux, treaty wordings, slips, performance reports, large-loss notifications. The format is reasonably consistent within a treaty over time but varies across treaties and across cedants. The reinsurer's accounting and underwriting functions consume these documents continuously.