Along for the Ride

Sharing insured risks with reinsurers usually eases carriers’ burden when liabilities arise, but that system is straining under the weight of mounting U.S. commercial casualty claims.

Driven by escalating litigation costs, traditional reinsurers are restricting capacity to limit exposure. To fill the resulting supply gap, private investors are putting their own capital on the line.

Over the past two years, sponsoring insurers, reinsurers, and specialized intermediaries have deployed an investor-fueled structure adapted from the property and life insurance sectors—sidecars. The vehicles allow third-party capital to participate directly in the reinsurance market. In practice, the casualty sidecar functions as reinsurance backing a specific portfolio of commercial liability risks, such as general liability, commercial auto, and workers compensation, underwritten by the sponsoring insurance company. Investors—primarily private equity, hedge funds, and large asset managers—supply the capital required to absorb these exposures, drawn by the prospect of diversified liability risks and uncorrelated returns.

The structure allows investors to target two distinct profit streams from a single allocation. First, they generate yield on the premium float. Because casualty claims often take years to settle, sidecars maintain substantial cash reserves. Asset managers can deploy this capital into higher-yield private credit and corporate bonds. Second, if the underlying insurance policies experience favorable loss ratios, investors capture the remaining premium as underwriting profit upon exiting the vehicle.

While sidecars have generally focused on short-tail lines, investor appetites are shifting, says Catherine Thomas, managing director at QBE Capital. According to Thomas, there has been a notable increase in interest from both sponsors and investors in long-tail sidecars. “They gain the ability to earn a return on that float by receiving premiums up front, while the claims are paid out over many years,” Thomas says. “It’s a compelling combination of access to underwriting and investment returns.”

For the sponsoring insurance company, the sidecar is a financial relief valve. By offloading a fixed percentage of liability risks to investors, the sponsor frees up room on its corporate balance sheet. The off-balance-sheet capital enables the insurer to underwrite new commercial policies and earn management fees without overextending its own capital reserves.

The capacity shortage stems from a steady expansion of commercial liabilities, including nuclear verdicts in third-party litigation, escalating workers compensation claims tied to cumulative trauma and an aging workforce, catastrophic ransomware and cyber extortion demands, and corporate class actions over biometric data privacy.

According to Marathon Strategies’ 2026 corporate litigation report, corporate jury awards of $10 million or more rose 40.7% in 2025, increasing to 190 verdicts from 135 the previous year; the combined verdicts totaled $25.6 billion. To put that into broader market perspective, a joint 2025 report by the Casualty Actuarial Society and the Insurance Information Institute revealed that rising jury awards, litigation financing, and evolving legal dynamics added between $231.6 billion and $281.2 billion to liability insurance losses from 2015 to 2024.

As traditional reinsurers retreat from soaring litigation costs, sidecars solve the primary carrier’s capacity dilemma by bringing external investor money directly into the liability market. At present, total disclosed capital in the casualty sidecar market has surpassed $2 billion, according to ratings agency AM Best. Prominent sponsors leading this evolution include QBE Re, Everest, Hamilton Insurance, and Ascot. While the casualty segment remains a small slice of the combined property and casualty sidecar market—valued by AM Best at between $17 billion and $19 billion— the ratings agency notes that these newer casualty vehicles now account for the vast majority of new capital entering the broader sidecar sector.

“The benefits of this capital influx are clear, given that the U.S. casualty business has been challenged for many years as a result of social inflation, litigation trends, adverse court decisions, and general political issues,” says Robert Hartwig, clinical associate professor of finance and insurance at the University of South Carolina. “To the extent that remnants of a hard market remain in the commercial property and casualty business, they are still concentrated on the casualty side. Consequently, there has been a clear need for additional capital that is both risk-tolerant and of a longer duration. Private capital and private equity meet both criteria, providing much-needed capacity to the industry.”

Sidecars’ History

Casualty sidecars represent the latest financial innovation within the global insurance market. Over the past 25 years, a variety of alternative risk transfer mechanisms and investor-backed vehicles have gained regulatory approval and market acceptance, including parametric insurance, collateralized reinsurance, and protected cell structures. Many of these innovations originated in Bermuda, favored for its specialized regulatory framework for alternative capital.

The property sidecar model emerged in 2001 when RenaissanceRe formed DaVinci Reinsurance to scale its underwriting capacity with external capital without diluting existing shares. Following the steep capital drain caused by Hurricane Katrina in 2005, reinsurers deployed sidecars to rapidly rebuild capacity, launching nearly 20 new vehicles the following year. These early structures protected corporate balance sheets from volatile weather risks while offering investors short-tail returns that typically cleared within a single annual underwriting cycle.

In 2019, the model expanded into the life insurance sector when retirement solutions specialist Athene established the Athene Co-Invest Reinsurance Affiliate (ACRA). ACRA enabled third-party investors to co-invest in blocks of annuity liabilities alongside the insurer. This framework optimized Athene’s capital efficiency while providing asset managers with predictable, long-duration portfolios ideal for funding private credit strategies.

Casualty sidecars function as a hybrid of these historical models. They partner the off-balance-sheet capacity framework pioneered in property catastrophe insurance with the long-term investment horizon of life insurance to absorb multiyear corporate liability risks. However, this extended litigation timeline introduces structural hurdles for traditional insurance-linked securities (ILS) investors, such as pension funds.

Typical pension funds allocate only a fraction of their alternative portfolios to insurance-linked securities, which have historically focused on short-tail property risks, says Ben Wright, managing director at Artex Capital Solutions, the ILS and structured transaction unit of Gallagher. Because institutional investment committees spent years becoming comfortable with that short-term model, long-tail casualty sidecars do not easily fit into their established asset allocations.

Wright notes that while property exposure is largely binary—a catastrophe either occurs or it does not—casualty lines face multiyear development uncertainty and variables such as social inflation. “Since casualty risk represents longer-tail lines of business where losses take time to mature, there is less clarity on the ultimate amount or severity of a loss,” he says.

To back these slow-developing losses, investors must tie up their capital for at least five years. While this extended duration deters liquidity-driven pension funds, it aligns neatly with the mandates of hedge funds and private equity managers to lock up capital for longer periods in order to capture higher returns. Such opportunistic capital providers are uniquely structured to withstand prolonged legal timelines, allowing them to wait out the process and maximize returns.

To meet these investors’ expectations for detailed tracking of their money and dedicated client service, the operational teams behind casualty sidecars function more like alternative asset managers. Major industry participants split their public financial reports into underwriting revenue, investment gains, and third-party management fees, according to Wright. “To support their operations, some sponsors and intermediaries now feature full investor relations teams, capital-raising infrastructure, and operational frameworks that rival midsize hedge funds,” he says.

Different Models

No two casualty sidecars are identical in design, risk profile, or underlying capital source. While traditional property catastrophe sidecars rely on largely standardized, fully collateralized frameworks, long-tail liability vehicles require highly customized structures to govern exposures lasting several years. Consequently, the sponsors orchestrating these programs vary significantly, ranging from traditional global reinsurers optimizing capital efficiency to front-line managing general underwriters (MGUs) securing exclusive coverage options for corporate clients.

In 2025, global reinsurer QBE Re sponsored its inaugural casualty sidecar, George Street Re. The placement was executed as a fully collateralized quota-share transaction exceeding $550 million. Under this proportional structure, the sidecar and the reinsurer split incoming premiums and potential claims by a fixed percentage, allowing QBE Re to share its risk while capturing additional underwriting capacity for its core cedents.

The structure leverages QBE’s Bermuda platform, QBE Capital, to link insurance risk with global investors. QBE Capital cedes casualty reinsurance risk to several cells of Mangrove Risk Solutions Bermuda, which is owned by insurance broker Marsh McLennan. Each cell’s assets and liabilities are legally ring-fenced.

The sidecar cells are funded by capital markets investors Culpeper Capital Partners and Calidris Investment Partners, along with specialty reinsurer Compre.

The primary hurdle for casualty sidecars has been to provide investors with a clear exit, usually within five to seven years. Historically, this has required the cedent to assume the remaining risk back onto their balance sheet. George Street Re overcomes this obstacle via Compre, offering a forward exit option for the other capital providers. “There’s more innovation in the market, with sponsors and investors exploring different ways of structuring these arrangements. The incorporation of forward-looking options is an example of this,” Thomas says.

Wholesale insurance brokers such as Amwins and Ryan Specialty take a different approach in developing casualty sidecars. Ryan Specialty’s sidecar, Ryan Alternative Capital (RAC Re), uses private equity cash as its financial engine. To deploy this capital, the sidecar plugs directly into Ryan Specialty’s MGU network, automatically taking a 10% quota-share slice across the broker’s multibillion-dollar international portfolio.

Because the sidecar takes a 10% quota share, it automatically receives the same percentage of all incoming premium revenue. In exchange, it is legally obligated to pay exactly 10% of every insurance claim that arises. There is no waiting period or deductible threshold—if a policyholder suffers a loss, the sidecar automatically cuts a check for its fixed share.

To transform the private equity backing into active insurance capacity, the capital is deployed into Bermuda-based RAC Re, which provides reinsurance support directly to Axis Capital’s Lloyd’s Syndicate 1686. Rather than relying on a traditional corporate deductible to absorb initial losses, this structure exposes investor capital to claims immediately. In exchange for taking on this first-dollar risk, investors maximize their yield potential by pulling in a premium share that would typically be retained by primary carriers.

To accommodate private equity investors that generally require a clear timeline for reclaiming their money, Ryan Specialty groups the investments into specific, time-limited cycles. The first cycle began accepting insurance business on Oct. 1, 2025, and will stop accepting new risks on Sept. 30, 2027. After that, a five-year winding-down period allows existing insurance claims to be settled. Once that period ends, a preplanned exit agreement automatically pays out the remaining funds to investors, who then have the option to roll their capital into the next cycle.

Managing these structured cycles requires a licensed partner, as private equity firms cannot issue policies directly or take on open-ended financial risks. To solve this, Axis manages the entire legal and payout process in exchange for a fee. Axis also builds in a specific financial cap on investor losses to protect investors from catastrophic losses.

To visualize how a single policy is actually split behind the scenes, it can be considered in pieces. A traditional insurance company issues the policy and covers the first 85% of the risk, leaving Axis to handle the remaining 15%. Axis keeps a 5% chunk on its own balance sheet, while the private equity sidecar “sits directly behind Axis, absorbing the remaining 10%,” says Miles Wuller, CEO of Ryan Specialty Underwriting Managers. This method of spreading massive commercial risks across multiple parties is standard practice in the specialty insurance market.

For the business buying the insurance policy, this complex machinery is completely invisible. The client simply receives a standard, seamless policy issued by Ryan Specialty.

Amwins rolled out an exclusive casualty sidecar, the Amwins Specialty Risk Underwriters Excess Casualty Sidecar, to address rising claims costs and shrinking market capacity for its commercial clients. Operating through its specialized underwriting division, Amwins acts as the managing general agent, running the program on behalf of institutional capital partners.

Under this follow-form model, the sidecar mirrors the exact terms, conditions, and pricing of a highly rated lead carrier to provide half of the coverage layer Amwins is placing. Helen Hawk, senior vice president at Amwins Special Risk Underwriters, explains that by halving individual risk exposure, the structure helps traditional carriers keep complex accounts while giving institutional investors access to a highly diversified pool of business. Over the past 12 months, the program has doubled its premium volume.

The sidecar soft-launched in October 2024 to a limited audience, followed by a full release in March 2025. “We began with a soft launch to allow the market to become accustomed to the concept,” Hawk says. “Our executive leadership recently met with our primary risk-bearing carriers, who expressed enthusiasm for the opportunity to share risk without keeping the entire financial burden on their own balance sheets.”

Potential Roadblocks

As the casualty sidecar market expands, its unique structure is drawing closer inspection from ratings agencies. At the Rendez-vous de Septembre annual industry meeting in Monte Carlo, AM Best introduced a note of caution regarding the segment’s rapid growth.

From a structural standpoint, AM Best views casualty sidecars’ multiyear timeline as a double-edged sword. On the positive side, the long-tail nature of the liabilities allows capital managers to maximize the value of the insurance float by investing accumulated premiums into higher-yielding, long-term assets. However, these extended durations create a clear disconnect between investor horizons and insurance liabilities.

Emmanuel Modu, managing director of global reinsurance and insurance-linked securities at AM Best, points out that while extreme long-tail lines like workers compensation can take up to 15 years to fully mature, institutional investors rarely want to lock up capital beyond a seven-to-10-year window. When investors exit, the outstanding liabilities must be cleanly transferred to them to prevent residual claims from reverting to the sponsor. This gap between the investor departures and the actual claim payouts creates tail risk when a sidecar doesn’t have enough capital to support its obligations, potentially exposing sponsoring insurers to worsening claims inflation and legal trends.

“The principal risks associated with casualty sidecars really start with the duration of the casualty liability, which can take years to develop,” says Modu. “Elements such as social inflation, litigation funding, nuclear verdicts, and legal trends can drive adverse reserve development.”

AM Best does not issue financial strength ratings for casualty sidecars; it only rates the sponsoring insurance companies. “We calculate possible capital shortfalls for each year of a sidecar’s life based on a rating-specific confidence level, based on the rating of the sponsor. The peak capital shortfall is charged directly against the sponsor’s available capital,” Modu says.

The threat to the industry is currently minor because the casualty sidecar market remains small, he adds. However, the ratings agency continues to stress-test sidecars based on their specific contract terms to protect the financial stability of the sponsoring carrier.

Meyer Shields, senior equity research analyst for property and casualty at investment bank and broker dealer Keefe, Bruyette & Woods, is generally bullish on casualty sidecars. While he warns that an insurer can incur heavy risk by placing all of its exposure into a single sidecar, Shields believes that structured tools like asset laddering, the scheduling of investments to mature at different times to match future claim payouts, help keep these dangers in check.

“If the [casualty] sidecar is managed properly through intelligent oversight on the part of companies, regulators, and rating agencies, it remains a manageable issue with a clear upside,” he says. “The cost of capital is lower, it generates more investment income, and it covers a broader spectrum of risk. To the extent that this alternative capacity has a lower cost of capital than traditional reinsurance, which appears to be the case, it can make insurance more affordable.”

The Road Ahead

It’s too early to predict how casualty sidecars will grow because most existing funds are still in their infancy. Growth could be limited by these vehicles’ requirement for a strict, long-term capital commitment. Unlike traditional stocks or bonds that can be sold quickly, sidecars tie up investor money for the years-long lifespan of the underlying insurance risks. Because investors cannot easily withdraw their cash if economic conditions change, mainstream capital providers could stay away, shrinking the pool of potential backers.

On the other hand, many alternative asset managers and private equity firms view multiyear commitments as a strategic fit. The extended timeline allows them to hold insurance premium float over several years and invest it directly into their long-term, high-yield private credit strategies.

A hint at what lies ahead is emerging as several of the older casualty sidecars will soon reach the end of their initial underwriting windows. Once these sidecars close, the funds will stop taking on new risks and focus on settling claims over the next several years. To continue backing new business, sponsoring insurance companies must approach investors to raise a fresh round of capital for a new fund cycle.

“This moment will serve as the first real test of investor satisfaction,” says Wright, explaining that if the early funds prove profitable, investors will readily back the next cycle. “Ultimately, the future growth of this market will depend on supply and demand, as an enormous volume of casualty insurance business requires capital, and institutional investors remain in continuous search of higher investment yields.”