Final answer:
The audit procedure in question is the Inspection of records or documents. It verifies the alignment of prices used by a billing program with the approved price list through detailed document examination.
Step-by-step explanation:
The audit procedure that involves tracing the prices used by the entity's billing program for pricing sales invoices to the entity's approved price list is known as Inspection of records or documents. This procedure is employed to verify whether the prices charged are consistent with those that have been officially approved by the entity. It entails a detailed examination of the relevant records, such as sales invoices and the official price list, to ensure that the pricing of goods or services has been done in accordance with the prescribed prices.