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A periodic inventory system updates inventory records at specific intervals like monthly or quarterly based on physical counts, whereas a perpetual system continuously tracks inventory in real time. The periodic approach relies on physical counts, which may cause delays and less accurate data compared to perpetual tracking. This makes periodic systems simpler but less responsive to inventory changes.

During the period, purchases are recorded in a purchases account, and sales are recorded in a sales account. The inventory account itself remains unchanged until a physical count is completed. Only after the physical count does the business update the inventory account and calculate the cost of goods sold based on the actual count results.

The periodic system is cost-effective and easy to implement, making it ideal for small businesses with limited resources. It avoids the need for advanced point-of-sale technology and continuous tracking systems. However, larger firms typically find it less suitable because it cannot provide real-time inventory insights needed for complex operations.

A significant limitation is that inventory records are only updated after each count, so losses from spoilage, theft, or human error may not be immediately identified. This delayed detection can lead to stockouts, overstocking, or unnoticed inventory discrepancies. Businesses lack real-time visibility into stock levels, which can impact decision-making and operational efficiency.

A grocery store may count its products at the end of each month. Employees count items on shelves and in storage, then use this count to update inventory records and calculate the cost of goods sold. This physical count process reveals any inventory changes that occurred during the month and reconciles the accounting records.

The cost of goods sold is not determined until the period ends, when a physical inventory count allows businesses to reconcile changes. During the period, purchases and sales are tracked separately in temporary accounts. Only after the physical count can the business calculate actual cost of goods sold and update the inventory balance.

Seasonal retailers or those with low inventory turnover often find the periodic method sufficient for their reporting needs. Bookstores, for example, might tally all items on hand every three months. The method prioritizes cost control over continuous monitoring, making it practical for operations where real-time inventory tracking is less critical.