Which of the following must an insurer obtain in order to transact insurance within a given state?

To transact insurance within a specific state, an insurer must obtain a certificate of authority. This certificate serves as formal permission granted by the state's insurance department, signifying that the insurer is legally authorized to conduct insurance business in that jurisdiction. This process typically includes providing proof of compliance with state laws and regulations, which often involves financial stability and adherence to ethical standards.

The certificate of authority ensures that the insurer meets specific solvency and operational criteria, which protects policyholders by ensuring that the insurer has the necessary resources to fulfill its obligations. Without this certificate, an insurer would be prohibited from selling insurance products or representing itself as an insurer in the state, which is crucial for maintaining regulatory integrity and consumer trust in the insurance market.