Cost of Goods Sold - Perpetual Inventory vs. Periodic Inventory: Videos & Practice Problems

The concept of cost of goods sold (COGS) is essential in understanding inventory management, particularly when comparing perpetual and periodic inventory systems. A perpetual inventory system continuously updates the inventory account after each sale, making it increasingly popular due to advancements like barcode scanning. This system allows for real-time tracking of inventory levels, which is crucial for businesses to manage stock efficiently.

When a sale occurs in a perpetual inventory system, two key entries are made. For instance, if a customer purchases an item for $15 that cost the company $5, the first entry records the revenue generated from the sale. This involves debiting cash for $15 (indicating an increase in cash assets) and crediting revenue for $15 (reflecting the income earned). The journal entry can be summarized as:

Debit Cash: $15
Credit Revenue: $15

The second entry pertains to the cost of goods sold. Here, the company debits COGS for $5 (an expense account that increases with the sale) and credits inventory for $5 (decreasing the asset as the item is no longer in stock). This entry can be expressed as:

Debit COGS: $5
Credit Inventory: $5

These entries impact the accounting equation, where assets increase by a net amount of $10 (cash up by $15 and inventory down by $5). While liabilities remain unchanged, equity is affected: revenue increases equity by $15, while the expense of COGS decreases it by $5, resulting in a net increase in equity of $10. This demonstrates the balance of the accounting equation, where total assets equal total liabilities plus equity.

In contrast, a periodic inventory system does not update inventory accounts after each sale. Instead, it calculates COGS at the end of a period by taking the beginning inventory, adding purchases, and subtracting the ending inventory. This method can be less accurate in real-time inventory tracking but may be simpler for some businesses.

Understanding these systems is crucial for effective inventory management and financial reporting, as they directly influence how a business tracks its sales, expenses, and overall financial health.

The periodic inventory system is a method of tracking inventory that updates the inventory account only at the end of the accounting period, contrasting with the perpetual inventory system, which continuously updates inventory records. In a periodic system, businesses record sales as revenue entries without immediately accounting for the cost of goods sold (COGS). For instance, when a customer purchases an item, the business records the cash received and the revenue generated, but does not record the cost associated with that item until the end of the period.

To illustrate, consider a scenario where a company sells an item for $15, which cost them $5. In a periodic inventory system, the only entry made at the time of sale is a debit to cash for $15 and a credit to revenue for $15. This increases both cash and equity, maintaining the balance in the accounting equation.

At the end of the accounting period, the business calculates COGS using the formula:

COGS = Beginning Inventory + Purchases - Ending Inventory

This formula allows businesses to determine the cost of goods sold by knowing the beginning inventory, the total purchases made during the period, and the ending inventory, which is determined through a physical count.

In a T-account format, the inventory account starts with a beginning balance (debit), and any purchases made during the period also increase the inventory (debit). Conversely, COGS, which represents the cost of items sold, is recorded as a credit, reducing the inventory balance. The relationship can be summarized as:

Beginning Inventory + Purchases - COGS = Ending Inventory

This visual representation helps in understanding how inventory flows through the account, making it easier to fill in known values and solve for unknowns. By using this method, businesses can effectively manage their inventory and ensure accurate financial reporting at the end of each accounting period.