An employer is issued a group medical insurance policy. The single contract is known as a(n)?

The term used for a single contract issued to cover a group, such as employees of an employer, is known as a Master Policy. This policy provides comprehensive coverage to all members of the group, making it distinct from individual policies, which are tailored to single individuals.

A Master Policy outlines the terms, conditions, and coverage specifics for the group, while each member might receive a certificate of coverage that details their individual benefits under the Master Policy. This structure is efficient as it allows the employer to manage insurance for multiple employees under one contract, rather than issuing separate policies for each individual.

The other options represent different concepts in insurance. A Sub Policy typically refers to a secondary or additional policy that provides coverage for specific situations or additional benefits, while an Individual Policy is specifically tailored for one person's insurance needs. A Policy Endorsement is an amendment or addition to an existing policy that alters the coverage. In contrast, the Master Policy encompasses the entire group under one single contract, which is why it is the correct answer.