What is commonly used to alter coverage or terms in an existing insurance policy?

The correct answer is endorsement, as an endorsement is specifically designed to modify the terms or coverage of an existing insurance policy. Endorsements are often used to add, remove, or change specific provisions within a policy without needing to issue a completely new policy.

For example, if a policyholder acquires a new vehicle, an endorsement can be added to include this vehicle under the current auto insurance coverage. Endorsements are official amendments that are documented clearly, ensuring that both the insurer and the insured have a mutual understanding of the altered terms.

The other options do not adequately fulfill this role. Exclusions refer to specific conditions or circumstances that are not covered by the policy, rather than a means to modify terms. An affidavit is a written statement confirmed by oath, primarily used for legal purposes, rather than for modifying insurance coverage. An attachment is not a defined term in insurance for modifying policy provisions; it may refer to a document related to a policy but does not specifically imply a change in coverage or terms.