Principles of Financial Accounting: Inventory - Effect of Inventory Methods on COGS, Gross Profit and Net Income

What It Is

Inventory methods, such as First-In-First-Out (FIFO), Last-In-First-Out (LIFO), and Weighted Average Cost (WAC), affect the calculation of Cost of Goods Sold (COGS), Gross Profit, and Net Income. If a company buys $10,000 of inventory at different costs, the choice of inventory method will impact the COGS and ultimately the Net Income. For example, using FIFO, the COGS might be $8,000, while using LIFO, it might be $9,000.

Key Concepts & Formulas

• FIFO (First-In-First-Out): Assumes the oldest inventory items are sold first. FIFO COGS = Beginning Inventory + Purchases - Ending Inventory. Example: If beginning inventory is $2,000, purchases are $8,000, and ending inventory is $3,000, the FIFO COGS would be $7,000 ($2,000 + $8,000 - $3,000).
• LIFO (Last-In-First-Out): Assumes the newest inventory items are sold first. LIFO COGS = Ending Inventory - Beginning Inventory + Purchases. Example: If beginning inventory is $2,000, purchases are $8,000, and ending inventory is $3,000, the LIFO COGS would be $7,000 ($3,000 - $2,000 + $8,000).
• WAC (Weighted Average Cost): Calculates the average cost of inventory based on the cost of goods available for sale. WAC COGS = Beginning Inventory + Purchases - Ending Inventory. Example: If beginning inventory is $2,000, purchases are $8,000, and ending inventory is $3,000, the WAC COGS would be $7,000 ($2,000 + $8,000 - $3,000).
• Gross Profit: Gross Profit = Sales - COGS. Example: If sales are $20,000 and COGS is $7,000, the gross profit would be $13,000.
• Net Income: Net Income = Gross Profit - Operating Expenses. Example: If gross profit is $13,000 and operating expenses are $5,000, the net income would be $8,000.

Journal Entry Examples

FIFO Example

Dr. Cost of Goods Sold $7,000 Cr. Inventory $7,000

Explanation: The company uses FIFO, so the COGS is $7,000. The inventory account is credited because it is being reduced by the COGS.

LIFO Example

Dr. Cost of Goods Sold $7,000 Cr. Inventory $7,000

Explanation: The company uses LIFO, so the COGS is $7,000. The inventory account is credited because it is being reduced by the COGS.

Common Mistakes

• Mistake: Confusing debits and credits for expense accounts.
• Correction: Expenses are debited, and revenues are credited. Use the mnemonic "DEBIT" (Decrease Expense, Balance Increases, Income, Taxes).
• Mistake: Not considering the impact of inventory methods on COGS and Net Income.
• Correction: Inventory methods can significantly impact COGS and Net Income. Use the FIFO, LIFO, and WAC methods to calculate COGS.
• Mistake: Not understanding the difference between COGS and Operating Expenses.
• Correction: COGS is the cost of goods sold, while Operating Expenses are the expenses related to the operation of the business. Use the formula Net Income = Gross Profit - Operating Expenses.

Exam Tips

• Tip: When calculating COGS, use the correct inventory method (FIFO, LIFO, or WAC).
• Tip: Remember that COGS is a direct expense, while Operating Expenses are indirect expenses.
• Tip: Be careful when reversing normal balances, as this can lead to incorrect calculations.

Quick Practice

1. A company uses FIFO and has beginning inventory of $5,000, purchases of $15,000, and ending inventory of $6,000. What is the COGS?
   • Answer: $14,000 ($5,000 + $15,000 - $6,000)
   • Explanation: The company uses FIFO, so the COGS is calculated using the FIFO formula.
2. A company uses LIFO and has beginning inventory of $5,000, purchases of $15,000, and ending inventory of $6,000. What is the COGS?
   • Answer: $14,000 ($6,000 - $5,000 + $15,000)
   • Explanation: The company uses LIFO, so the COGS is calculated using the LIFO formula.

Last-Minute Cram Sheet

• Inventory methods (FIFO, LIFO, WAC) affect COGS and Net Income.
• FIFO COGS = Beginning Inventory + Purchases - Ending Inventory.
• LIFO COGS = Ending Inventory - Beginning Inventory + Purchases.
• WAC COGS = Beginning Inventory + Purchases - Ending Inventory.
• Gross Profit = Sales - COGS.
• Net Income = Gross Profit - Operating Expenses.
• Expenses are debited, and revenues are credited.
• COGS is a direct expense, while Operating Expenses are indirect expenses.
• Reversing normal balances can lead to incorrect calculations.