Facultative reinsurance is coverage purchased by a primary insurer to cover a single risk -or a block of risks-held in the primary insurer's book of business. Facultative reinsurance is one of two types of reinsurance (the other type of reinsurance is called treaty reinsurance). Facultative reinsurance is considered to be more of a one-time transactional deal, while treaty reinsurance is typically part of a long-term arrangement of coverage between two parties.