Causes of difference in net operating income under variable and absorption costing

By: Rashid Javed | Updated on: November 14th, 2021

Variable costing and absorption costing usually produce different net operating income figures. The reason is that the fixed manufacturing overhead cost is not treated the same way under two costing methods.

To understand how the difference in treatment of fixed manufacturing overhead cost changes the net operating income figures of two costing systems, we need to prepare two income statements, one under variable costing and one under absorption costing. For this purpose, consider the following example:


A company prepares variable costing income statement for the use of internal management and absorption costing income statement for the use of external parties like creditors, banks, tax authorities etc. The company manufactures a product that is sold at a price of $80 per unit. The variable and fixed cost data is given below:

Direct materials: $30.00
Direct labor: $19.00

Factory over head:
Variable cost: $6.00
Fixed cost ($45,000/9000 units): $5.00

Marketing, general and administrative:
Variable cost (per unit sold): $4.00
Fixed cost (per month): $28,000

During the month of June, 9,000 units were produced and 7,500 units were sold.  The opening inventory was 2,000 units.


  1. Prepare two income statements, one using variable costing method and one using absorption costing method.
  2. Explain the reason of difference in net operating income (if any) under two approaches.


(1) Income statements

(a). Absorption Costing:


*Computation of units in ending inventory:


(b). Variable Costing:


Reconciliation of net operating income:


(2). Explanation of the difference in net operating income:

Notice that the net operating income under absorption costing is $7,500 ($92,000 – $84,500) higher than the net operating income under variable costing. This difference of net operating income is because of fixed manufacturing overhead that becomes the part of ending inventory under absorption costing but not under variable costing system.

The ending inventory absorbs a portion of fixed manufacturing overhead and reduces the cost burden of the current period. Consequently, a portion of fixed cost that relates to the current period is transferred to the next period. This is typically known as the deferring of fixed cost in the inventory. In our example, the portion of fixed overhead deferred in inventory is $7,500 (= 1,500 units x $5).

Under variable costing, the fixed manufacturing overhead cost is not included in the product cost but charged to the income statement of the relevant period in its entirety. Therefore, no portion of fixed cost can be absorbed by the ending inventory.

In our example, the net operating income is higher under absorption costing than under variable costing because closing inventory units are greater than the opening inventory inventory units.

Important points to remember:

Students always need to remember the following key points while solving their questions related to variable and absorption costing income statements:

  1. The net operating income under absorption costing systems is always higher than variable costing system when inventory increases during the period.
  2. The net operating income under variable costing systems is always higher than absorption costing system when inventory decreases during the period.
  3. When inventory increases, the fixed manufacturing overhead cost is deferred to inventory which reduces the current period’s total cost burden.
  4. When inventory decreases, the fixed manufacturing overhead cost is released from inventory which causes an increase in the current period’s total cost burden.
14 Comments on Causes of difference in net operating income under variable and absorption costing
  1. ici

    Hello! Thank you for this post but are you really sure about what you’re saying? Do you have more sources for us? thank you

  2. Rashid Javed

    @iCi if you read all the articles posted in this topic (category) you will understand the whole concept. We also have exercises and problems for the topic “variable and absorption costing”. Thank you for your interest.

  3. mgmt acctg

    Thanks for this post. I compared my books about managerial accounting and this is more comprehensive.

  4. tiey

    Hi there,
    I have data stated the sales is 10,000 higher than the product, without any begining inventories.
    How will the statement look like? How i am going to compute the less production? Is it need to be add on to the cost of good sold? Then deducted from the sales? But there are no production for that…

  5. Madhav Subedi

    Which Method will have higher NOI when all units are sold? Isn’t the NOI will be the same? Please answer me. Thank You.

    1. Shreshth Kumar Upadhyay

      Absorption costing method.

  6. Gabriel Vutnamur

    This post is very useful for at this time where I’m doing a major assignment specifically under this topic. Thank you so very much!

  7. Robert rassam

    Very comprehensive example – easy to understand – and very accurate – thanks for sharing

  8. Natalie

    Wow, great explanation. Much clearer than my text book. Thank you!

  9. fetsum

    10qqqqqq too much. it is very useful

  10. Sultan Alshekaili

    This is wrong it means that you ignored the fixed manufacturing overhead from the calculation of operating income under variable costing which should had been treated as selling and administrative expenses. That is in absorption method the fuxed manufacturing overhead is product cost and in variable costing it is selling and administrative expenses (period cost).


    This is very useful to me,very clear since i dont understand the concepts during lectures.

  12. Abdulhakim sheko

    it’s good

Leave a comment