Insurers must complete claims investigations:

The requirement for insurers to complete claims investigations "promptly" reflects the regulatory standard that aims to ensure fair and timely processing of insurance claims. This term emphasizes the importance of efficiency and responsiveness in handling claims without a specific deadline that may not accommodate all cases.

Using "promptly" allows for some flexibility, recognizing that while insurers must act quickly to serve the policyholder's needs, certain claims may require more detailed investigation due to complexity or the need for additional information. This aligns with the expectation that insurers treat their clients fairly and act in good faith, helping to maintain trust in the insurance system.

In contrast, the other options impose more rigid timeframes that may not be practical for all claims situations. While completing claims investigations "as soon as possible" suggests urgency, it does not provide a standard for evaluating whether the timeline was met. The deadlines of "within 30 days" or "within 90 days" could potentially lead to situations where insurers hastily conclude investigations to meet the deadline, rather than thoroughly evaluating them. Therefore, "promptly" strikes a balance between urgency and the need for thoroughness in claims processing.