The provision which requires an insurer to pay benefits immediately upon receipt of an acceptable written proof of loss submitted by an insured is:

The notice of claim is the initial communication from the insured to the insurer informing them of a potential claim. It serves as the first step in the claims process by alerting the insurance company of a possible loss or event triggering coverage, but it does not directly relate to the requirement for immediate payment of benefits upon proof of loss.

A grace period is the specified duration after the premium due date during which the policyholder can make a payment without incurring a penalty or coverage lapse. It is a provision designed to provide flexibility to policyholders in meeting their financial obligations but does not pertain to the prompt payment of benefits following the submission of proof of loss.

A reinstatement claim involves the restoration of a lapsed insurance policy to its original active status after the policyholder fulfills certain requirements, such as paying outstanding premiums. This process is distinct from the immediate payment of benefits upon submission of proof of loss required by the timely payment of claim provision.