What encompasses any written document that modifies an insurance policy?

The correct choice is endorsements, as this term refers specifically to any written document that modifies an insurance policy. Endorsements can be used to add, change, or exclude coverage details. They are formal additions to the insurance contract that alter the terms or details of the policy without issuing an entirely new policy. This is significant for both insurers and insureds because it allows for flexibility in coverage as circumstances change, ensuring that the policy accurately reflects the needs of the policyholder.

Understanding endorsements is crucial, as they can clarify or change the policy language, extending or limiting coverage based on the mutual agreement between the insurer and the insured. This adaptability is important in managing risks and ensuring that the insurance coverage remains relevant and useful over time.