AM Best has upgraded the Long-Term Issuer Credit Rating (Long-Term ICR) to “aa” (Superior) from “aa-” (Superior) and affirmed the Financial Strength Rating (FSR) of A+ (Superior) of MS Amlin AG (MS Reinsurance) (Switzerland). The outlook of the Long-Term ICR has been revised to stable from positive while the outlook of the FSR is stable. The company is a subsidiary of Mitsui Sumitomo Insurance Company, Limited (MSI).

The Credit Ratings (ratings) reflect the consolidated balance sheet strength of MSI, which AM Best assesses as strongest, as well as its strong operating performance, favorable business profile and appropriate enterprise risk management.

The Long-Term ICR upgrade reflects the assignment of full rating enhancement to MS Reinsurance due to the increased strategic and financial importance to its parent, MSI. The ratings of MSI are being extended to MS Reinsurance given the implicit and explicit support provided, the latter in the form of a full unconditional parental guarantee.

MS Reinsurance has grown in recent years and accounts for a significant portion of MS&AD Insurance Group Holdings, Inc. (MS&AD) and MSI’s international premiums and profits. The company, with its operating hubs in Zurich, Bermuda and the United States, is a key platform for MS&AD’s strategy to increase its exposure to international markets and differentiate its premium and profit base geographically. MS Reinsurance is the group’s global reinsurance platform and wrote gross premiums of approximately USD 4 billion in 2025.

This press release relates to Credit Ratings that have been published on AM Best’s website. For all rating information relating to the release and pertinent disclosures, including details of the office responsible for issuing each of the individual ratings referenced in this release, please see AM Best’s Recent Rating Activity web page. For additional information regarding the use and limitations of Credit Rating opinions, please view Guide to Best’s Credit Ratings. For information on the proper use of Best’s Credit Ratings, Best’s Performance Assessments, Best’s Preliminary Credit Assessments and AM Best press releases, please view Guide to Proper Use of Best’s Ratings & Assessments.

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