Which type of beneficiary cannot be changed without the beneficiary's written consent?

The correct answer is irrevocable beneficiary. An irrevocable beneficiary designation means that the policyholder cannot change the beneficiary without obtaining the written consent of that beneficiary. This protects the rights of the irrevocable beneficiary, ensuring that they are guaranteed to receive the policy’s benefits upon the policyholder's death, unless they agree otherwise.

In contrast, a primary beneficiary can be changed freely by the policyholder without needing permission from that beneficiary. A contingent beneficiary serves as a backup and can also be changed without the need for consent. A revocable beneficiary designation allows the policyholder to modify the beneficiary designation at any time without needing consent, making it flexible compared to the irrevocable option. Therefore, the fundamental difference lies in the level of protection and rights given to the irrevocable beneficiary compared to other types.