Final answer:
To test for unbilled shipments, tracing from shipping documents to sales records and accounting entries is effective. This helps to confirm all shipped goods are billed and correctly recorded, which is important in measuring the balance of merchandise trade, tracking the physical goods exchanged in international trade.
Step-by-step explanation:
An effective procedure to test for unbilled shipments is to trace from the shipping documents to the sales records and accounting entries. This method helps to ensure that all goods shipped are appropriately billed and recorded in the financial statements. In the context of international trade, tracking the solid or physical items that planes, trains, and trucks transported between countries was a widespread practice to measure the balance of trade, which economists refer to as the balance of merchandise trade. This measurement focuses on the value of a country's exports of goods versus its imports of goods, excluding services, intellectual property, and other non-physical products.