Which insurance type code is used to identify an auto insurance policy as the primary payer?

The code used to identify an auto insurance policy as the primary payer is "AP." This designation is critical in claims processing, especially when determining the order of payment among multiple insurance sources. In situations where a patient has both auto insurance and other forms of health coverage, the primary payer is responsible for covering the medical costs first. By identifying the auto insurance as the primary payer with this code, healthcare providers and insurers can streamline the billing process and avoid delays in payment for services rendered.

The other options represent different types of insurance or are used in other contexts and do not pertain to the identification of auto insurance specifically as the primary payer. Hence, selecting "AP" correctly aligns with the established coding system used in the healthcare industry to classify insurance information for accurate claims submission.