Final answer:
The periodic inventory system updates inventory units and costs only at the end of a reporting period through physical count and accounting adjustments.
Step-by-step explanation:
The question is referring to an accounting method known as the periodic inventory system. In this system, inventory units and costs are only updated at the end of a reporting period via a physical count and adjustments to the accounting records.
The opposite system is known as the perpetual inventory system, where inventory records are updated continuously as transactions occur. Under the periodic system, a company would typically conduct a physical inventory count at the end of the year, quarter, or month, and the cost of goods sold (COGS) is calculated based on this count and additional purchases made throughout the period.