Absorption vs. variable costing: impact on inventory and income

Learning outcome statements

The learning outcome statements relevant for this section are:

1. demonstrate an understanding of variable (direct) costing and absorption (full) costing and the benefits and limitations of these measurement concepts
2. calculate inventory costs, cost of goods sold, and operating profit using both variable costing and absorption costing
3. demonstrate an understanding of how the use of variable costing or absorption costing affects the value of inventory, cost of goods sold, and operating income
4. prepare summary income statements using variable costing and absorption costing

Effect on inventory and income

There are two primary approaches to assigning manufacturing costs to products:

• Absorption (full) costing includes all manufacturing costs, both variable and fixed, in the cost of a product. This method is required for external financial reporting under U.S. GAAP and IFRS.
• Variable (direct) costing includes only variable manufacturing costs (direct materials, direct labor, and variable manufacturing overhead) in product costs. Fixed manufacturing overhead is treated as a period cost and expensed in full during the period incurred. Variable costing is often used for internal decision-making and performance analysis.

The key differences in cost treatment are summarised below. You will see that the main difference is the fixed manufacturing overhead.

Cost Element	Absorption Costing	Variable Costing
Direct Materials	Product Cost	Product Cost
Direct Labor	Product Cost	Product Cost
Variable Manufacturing Overhead	Product Cost	Product Cost
Fixed Manufacturing Overhead	Product Cost	Period Cost
Selling & Admin expenses (Fixed and Variable)	Period Cost	Period Cost

A key distinction between absorption and variable costing lies in how they treat fixed manufacturing overhead, which leads to notable differences in inventory valuation, cost of goods sold (COGS), and ultimately, operating income.

Effects on inventory valuation

Under absorption costing, fixed manufacturing overhead is included in the cost of each unit produced and is capitalized as part of inventory (whether sold or not). As a result, when production exceeds sales, ending inventory absorbs a portion of the fixed overhead, making the value of inventory on the balance sheet higher.

In contrast, under variable costing, only variable manufacturing costs are included in inventory. Fixed overhead is treated as a period cost, meaning it is expensed in full regardless of the level of production. Therefore, ending inventory is lower compared to absorption costing.

Example:
Suppose a company produces 1,000 units and sells 800 units during the period. The fixed manufacturing overhead is $10,000 and the variable manufacturing costs total $6 per unit.

• Under absorption costing, $10 of fixed OH ($10,000 ÷ 1,000) is included in the product cost. The 200 unsold units will include $2,000 of fixed overhead in inventory.
• Under variable costing, this $2,000 is not deferred and is expensed entirely in the current period, included in the $10,000 fixed manufacturing overhead expense for the period.

Effects on cost of goods sold (COGS)

Because absorption costing treats fixed overhead as product costs and spreads fixed overhead over all units produced, the portion of fixed overhead associated with unsold inventory remains on the balance sheet and is not expensed in the current period.

As a result, when inventory increases (more units produced than sold), under absorption costing:

• COGS appears lower (since fewer units are expensed), and
• Operating income appears higher than under variable costing.

On the other hand, variable costing recognizes all fixed overhead immediately as a period cost, so the COGS is unaffected by changes in inventory levels. It should be noted that COGS is composed solely of product costs.

Example (continued):

• Absorption COGS = 800 units × ($6 variable + $10 fixed OH per unit) = $12,800
• Variable COGS = 800 units × $6 = $4,800

Under absorption costing, the remaining $2,000 (from 200 unsold units × $10 fixed OH) is not expensed immediately. Instead, it is included in ending inventory on the balance sheet.

Under variable costing, the entire $10,000 of fixed manufacturing overhead is expensed in full in the current period, appearing under period costs in the income statement. See the impacts in the operating income below.

Effects on operating income

The selection of costing method affects the timing of fixed overhead recognition and can lead to differences in reported operating income. These differences arise when there is a mismatch between the number of units produced and the number of units sold.

Example 1
When a company produces more units than it sells, some of the fixed overhead is deferred in inventory under absorption costing, while variable costing expenses all fixed overhead immediately.

• Units produced: 10,000
• Units sold: 8,000
• Total fixed manufacturing overhead: $40,000
• Absorption overhead rate: $40,000 ÷ 10,000 = $4 per unit
• Ending inventory: 2,000 units

Effect:

• Under absorption costing, $8,000 (2,000 × $4) of fixed overhead is deferred in inventory.
• Under variable costing, all $40,000 is expensed in the current period.

Income Comparison:

• Absorption costing:
  • COGS includes only $32,000 of FOH
  • Operating income is $8,000 higher
• Variable costing:
  • All $40,000 FOH expensed
  • No FOH deferred in inventory

Example 2
When sales exceed production, the company must sell from beginning inventory (assuming the company uses FIFO). Under absorption costing, any fixed overhead embedded in that inventory is released into cost of goods sold, while under variable costing, this does not occur because FOH is never inventoried.

• Units produced: 8,000
• Units sold: 10,000
• Beginning inventory: 2,000 units (carrying $3 FOH per unit from prior period)
• Current fixed overhead: $40,000
• Absorption rate this period: $40,000 ÷ 8,000 = $5 per unit

Effect:

• FOH in COGS under absorption includes:
  • $6,000 from beginning inventory (2,000 × $3)
  • $32,000 from current production (8,000 × $4)
  • Total FOH in COGS: $38,000
• Under variable costing:
  • All $40,000 FOH expensed in the current period

Income Comparison:

• Operating income will differ between the two methods.
• The difference is not the mirror opposite of Scenario A because the fixed overhead embedded in beginning inventory impacts the absorption method’s COGS. This additional factor makes the income effect less predictable when sales exceed production.

Benefits and limitations

Absorption (full) costing

Benefits:

• Absorption costing complies with U.S. GAAP and IFRS. It is the only acceptable method for preparing external financial statements and tax filings in many jurisdictions.
• By including both variable and fixed manufacturing costs in inventory, this method ensures that all costs incurred to bring products to a saleable condition are matched with the revenues they help generate, following the matching principle in accounting.
• It helps stakeholders understand the total cost to produce goods, which is useful for pricing, quoting, and long-term planning.

Limitations:

• Because it blends fixed costs into inventory, it makes it harder to conduct cost-volume-profit (CVP) analysis, break-even analysis, or short-term decision-making, where distinguishing fixed vs. variable behavior is critical.

Variable (direct) costing

Benefits:

• By treating fixed manufacturing overhead as a period cost, variable costing provides a clearer view of cost behavior, helping managers understand how costs change with activity levels.
• Since fixed and variable costs are separated, variable costing is ideal for internal reporting focused on decision-making, such as break-even analysis, contribution margin analysis, and short-term operational planning.

Limitations:

• Variable costing does not comply with GAAP or IFRS for external financial statements. It is strictly used for internal decision support.
• By excluding fixed manufacturing overhead from inventory, it can understate asset values on the balance sheet, particularly in capital-intensive industries where fixed costs form a large portion of total manufacturing cost. For example, a company with high depreciation and factory rent may show much lower inventory values under variable costing, which could impact management’s perception of inventory efficiency or profitability.