Category: Reinsurance brokers and structures · Reviewed by Matt Bartlett, Director · Founder · Last reviewed 2026-06-05
A multi-line treaty is a reinsurance treaty covering multiple classes of underlying insurance under a single placement — for example, combined property and casualty quota share, or composite cover across motor, property and liability portfolios. The structure provides diversification benefit for the cedant and breadth for the reinsurer.
Category: Reinsurance brokers and structures Also known as: composite treaty, multi-class treaty Related concepts: reinsurance treaty, variable quota share, proportional reinsurance
Multi-line treaties cede multiple classes of underlying insurance under a single set of terms. The cession rate and other terms may be uniform across the classes or differentiated by sub-class (in which case the treaty may be structured as a variable quota share).
The structure is most commonly used by composite insurers with diversified portfolios who wish to consolidate their reinsurance purchasing for administrative efficiency and aggregate diversification recognition. The reinsurer benefits from access to a diversified book that may exhibit less aggregate volatility than any individual class.
Multi-line treaties are documented under the Market Reform Contract format with a schedule of underlying classes and cession terms. The duty of fair presentation under the Insurance Act 2015 [1] applies to all classes.
Multi-line treaties are typical for SME-focused composite insurers who write commercial property, motor, liability and BI under a single brand. The treaty cedes all these classes to a small panel of reinsurers, with quarterly bordereaux split by class for accurate accounting.
For larger composite groups, separate single-class treaties for each major line are typically preferred — they allow more specialised reinsurer participation, more refined pricing and clearer accountability.
An illustrative example: a regional UK SME insurer cedes its commercial property, motor, public liability and BI portfolios under a single 30 per cent multi-line quota share treaty placed with a panel of three reinsurers. The treaty includes a flat 30 per cent ceding commission across all classes, with profit commission calculated on the aggregate three-year result.
This entry is part of the Apex Insurance Wiki. Last reviewed by Matt Bartlett on 2026-06-05. Next review: 2026-12-05.
Apex Insurance Brokers Limited. Authorised and regulated by the Financial Conduct Authority, FRN 724952. Registered in England and Wales, Companies House 07014570. This entry provides general information about UK insurance concepts and is not regulated advice. Consult your insurance broker on your specific position.
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