Job order costing: accounting for spoilage

Accounting for normal and abnormal spoilage

In a job order costing system, spoilage - units of production that do not meet the specifications for good units and are discarded or sold for disposal value - can occur during production. It is essential to classify spoilage correctly, as this affects both inventory valuation and the reporting of expenses in the income statement. Spoilage is typically categorized as either normal or abnormal, based on its nature and cause.

Recall from the previous chapter that costs flow through work-in-process to finished goods and then to cost of goods sold as direct materials, direct labor, and applied overhead accumulate by job; spoilage adjusts those job costs along the way.

Normal spoilage

Normal spoilage refers to waste that is expected or unavoidable under efficient operating conditions. It is considered part of the regular cost of manufacturing and is typically absorbed by good units produced.

• If the spoilage is job-specific, the cost is assigned to the job itself.
• If the spoilage is common to all jobs, it is treated as part of manufacturing overhead and allocated accordingly.

Example: Normal spoilage

A furniture manufacturer expects 2 defective tables per 100 due to wood warping. If 2 units are spoiled during Job #212 (which produced 100 units), the spoilage is considered normal and is included in the cost of Job #212. Because this spoilage is specific to Job #212 and has no disposal value, no journal entry is required - its cost flows into inventory or COGS along with the good units.

Answer: No entry required; the cost of the 2 spoiled units remains part of Job #212.

Normal spoilage common to all jobs: when spoilage isn’t tied to one job, its net cost moves out of work-in-process and into overhead instead of staying with the job:

• Debit manufacturing overhead control for the net cost of the spoiled units
• Debit materials control for any disposal (salvage) value the spoiled units can be sold for
• Credit work-in-process – job # for the total cost of the spoiled units

Because this type of spoilage is expected, its cost is already built into the predetermined overhead rate used to apply overhead to jobs.

Abnormal spoilage

Abnormal spoilage arises from unexpected and avoidable causes, such as operator errors, equipment failure, or substandard inputs. Since these losses are not considered part of efficient operations, they are treated as period costs and expensed immediately on the income statement.

• Abnormal spoilage is not included in inventory valuation.
• It is recorded as a separate expense line under operating costs or “loss from abnormal spoilage.”

Pitfall: the denominator in the formula below is total units net of the expected normal loss, not total units produced. This spreads the cost of normal spoilage across the good units while isolating only the abnormal portion for the period-expense calculation.

To compute the cost assigned to abnormal spoilage:

$$\text{Abnormal spoilage cost}=(\frac{\text{Total cost}}{\text{Total units}–\text{Normal loss units}})\times \text{Abnormal spoilage units}$$

Where:

• Total cost = combined cost of direct materials, direct labor, and applied overhead
• Normal loss units = expected spoilage under efficient conditions
• Abnormal spoilage units = excess spoilage beyond normal expectations

Example: Abnormal spoilage

A batch of 1,000 units has a total cost of $12,000. The company expects normal spoilage of 2% (20 units), but 35 units were spoiled. This results in 15 units of abnormal spoilage.

$$\begin{array}{rl}\text{Abnormal spoilage per unit}& =(\frac{\text{Total cost}}{\text{Total units}–\text{Normal loss units}})\\ & =(\frac{12,000}{1,000–20})\\ & =(\frac{12,000}{980})\\ & =12.2449\end{array}$$

$$\begin{array}{rl}\text{Cost of abnormal spoilage}& =\text{Abnormal spoilage per unit}\times \text{Abnormal spoilage units}\\ & =12.2449\times 15\\ & =183.67\end{array}$$

Answer: The abnormal spoilage cost is $183.67 (using the unrounded per-unit cost, rather than a rounded $12.24), charged as a period expense.

Assume the abnormal spoilage cost of $183.67 (as computed earlier) occurred during Job #412 due to a machine malfunction.

Transaction	Debit	Credit	Explanation
Record abnormal spoilage	Loss from abnormal spoilage: $183.67	Work-in-process – Job #412: $183.67	To recognize the cost of abnormal spoilage as a period expense

The debit goes to an income statement account, often titled “loss from abnormal spoilage” or similar while the credit removes the cost of spoiled units from WIP to avoid overstating inventory.

If the spoiled units instead have a disposal (salvage) value - for example, they can be sold as scrap - that recoverable amount reduces the loss rather than being fully expensed. The entry becomes: debit materials control for the disposal value, debit loss from abnormal spoilage for the net cost (total cost minus disposal value), and credit work-in-process – Job #412 for the total cost of the spoiled units.

Benefits and limitations of job order costing

Understanding the strengths and constraints of the job order costing system helps organizations determine whether it is the appropriate costing approach for their operations. This section summarizes the most important benefits and limitations.

Benefits of job order costing

• Direct materials and labor are traced to individual jobs, giving precise cost visibility at the job level.
• Ideal for industries where each job or batch is unique (e.g., construction, consulting, legal, and custom manufacturing).
• By identifying the actual cost of each job, businesses can price accurately and evaluate the profitability of specific contracts or clients.
• Departments or project teams can be held responsible for job-specific cost overruns or savings.
• Particularly for service firms, job costing allows for detailed billing and transparent explanations of charges.

Limitations of job order costing

• Requires detailed tracking and documentation of costs for each job, increasing administrative workload.
• Overhead is applied using predetermined rates, which may lead to under- or overapplied overhead, distorting true job costs.
• In industries with homogeneous, repetitive output, process costing is typically more efficient.
• Especially for smaller organizations or firms with limited resources, the system may be burdensome.
• If overhead drivers are poorly chosen, overhead costs may not reflect true resource consumption, leading to inaccurate cost assignments.