A controller costing a custom yacht and a controller costing a barrel of gasoline run different systems for one reason: the yacht is unique and the gasoline is not. The exam rewards the candidate who names the system first, traces the cost flow second, and applies spoilage and ABC rules third.
Manufacturing costs flow through three inventory accounts: Raw Materials, Work-in-Process (WIP), and Finished Goods. Direct materials and direct labor flow into WIP; manufacturing overhead is applied to WIP using a predetermined rate. Completed units move from WIP to Finished Goods, and when sold they flow to Cost of Goods Sold (COGS) on the income statement.
Job-order costing applies when output is heterogeneous and traceable. Custom homebuilders, audit firms, hospitals, and aircraft manufacturers run job-order systems. Each job carries its own cost record; materials and labor are charged from source documents (requisitions, time tickets), and overhead is applied using a predetermined rate.
Process costing applies when output is homogeneous and continuous. Refineries, cement plants, paper mills, and food processors run process costing.
Common mistakes
- Charging all spoilage to the period. Only abnormal spoilage hits the income statement directly. Normal spoilage is a product cost loaded into good units or absorbed in the overhead rate.
- Picking job-order when output is homogeneous. A cement plant does not run job-order. The signal is product heterogeneity, not company size. Identical continuous output means process costing.
- Confusing cost driver with resource driver. Resource drivers assign general-ledger costs into activity pools; activity drivers assign pool cost out to products. The exam swaps the labels.
Bottom line
- Job-order costing tracks costs to unique jobs; process costing averages costs across identical units; operation costing is the hybrid
- Normal spoilage is a product cost loaded into good units; abnormal spoilage is a period loss hitting the income statement directly
- Equivalent units convert partially complete WIP into whole-unit equivalents; weighted average and FIFO are the two methods
- ABC replaces a single volume base with multiple drivers, shifting cost from high-volume simple products to low-volume complex ones
Exam shortcut
When the fact pattern names a continuous, homogeneous product (oil, paper, chemicals), default to process costing with equivalent units. When the product is named or customer-specific (audit, custom build, lawsuit), default to job-order. When the question contrasts traditional and ABC overhead, expect the low-volume complex product to be undercosted under traditional and corrected upward under ABC. The trap answer reverses the direction.
The full lesson (about 1,892 words, 13 min read) adds 2 worked examples, all 6 common mistakes, a self-check, free in the app.
Learning objectives
- 1D2
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