In the USA this is a broker who is licensed to place coverage with nonadmitted insurers (insurers not licensed to do business in a given state). Surplus Lines Insurers can write coverage through a Surplus Lines Broker, if the broker is licensed in the State where the coverage is being written. The types of risks typically written by Surplus Lines Brokers are generally substandard risks (e.g., risks with adverse loss experience), unusual risks, and risks for which there is a shortage of capacity in the admitted market.
The Surplus Lines Insurer writes coverage that need not be filed with the State insurance departments as a condition of being able to offer coverage. The types of risks typically insured in the Surplus Lines Insurance Marker can usually be categorised as risks with adverse loss experience, unusual risks, and those for which there is a shortage of capacity within the standard market.
Not surprisingly the London Insurance Market and in particular Lloyd's of London is generally the final destination where such risks are underwritten. With the exception of Illinois and kentucky, Lloyd's syndicates writing business in the USA do so as non admitted insurers - they are not licensed to do business in a certain state.