ACF5955 Chap.4 Overhead Allocation and ABC
Overhead Allocation and ABC
Overhead allocation assigns indirect resources to cost objects, but a broad volume base can distort product costs when complexity differs. Activity-based costing routes resource cost through activity pools and causal drivers such as setups or inspections.
This chapter compares traditional and ABC assignments, classifies unit, batch, product and facility activities, considers practical capacity, and separates full allocated cost from avoidable decision cost. Students learn to predict the direction of a cross-subsidy, reconcile both systems to the same pool, and explain why a product's cost shifts.
The analysis also asks whether driver data is worth maintaining and whether unused capacity should remain visible rather than being forced into product rates. These distinctions matter before management changes prices, redesigns processes or removes an apparently costly line.
What this chapter covers
- 01
Plantwide and departmental rates
- 02
Product-cost cross-subsidy
- 03
Activity cost pools
- 04
Resource and activity drivers
- 05
Driver hierarchy levels
- 06
Unused capacity and facility costs
Worked example · free
Shift setup cost with activity-based costing
- +2Setup rate is $72,000 divided by 120, which equals $600 per setup.
- +2Machine-support rate is $108,000 divided by 9,000, which equals $12 per hour.
- +2Standard receives $12,000 setup plus $72,000 machine support, totalling $84,000.
- +2Custom receives $60,000 setup plus $36,000 machine support, totalling $96,000; assignments reconcile to $180,000.
Key terms
- Activity cost pool
- An activity cost pool groups resources consumed by a defined activity.
- Activity driver
- An activity driver measures how a cost object consumes an activity.
- Cross-subsidy
- A cross-subsidy occurs when one cost object receives cost caused by another because the allocation base is distorted.
- Practical capacity
- Practical capacity is the attainable resource supply after allowing for normal operating interruptions.
Overhead Allocation and ABC FAQ
When is activity-based costing most useful?
It is most promising when overhead is material, outputs differ in complexity and a broad volume base poorly represents support demand. The expected decision benefit must still justify collecting and maintaining additional driver data.
Why can a unit-based rate distort batch cost?
Batch activities occur once for a group rather than once for every unit. Allocating setup or inspection cost by units makes large batches absorb more cost even when small batches trigger more support events.
Should a product be dropped when its ABC cost rises?
Not automatically. Verify the causal drivers, identify which activity resources are avoidable, consider customer and strategic effects, and test whether released capacity has another use. ABC diagnoses consumption but does not replace relevant-cost analysis.
Exam move
Draw the two-stage route from resources to activities and from activities to cost objects. Calculate every rate with its driver unit, reconcile assignments and explain the causal reason for any shift. For evaluation questions, discuss diversity, overhead significance, driver quality, unused capacity and the cost-benefit tradeoff. Do not treat facility allocations as incremental cash flows without evidence.
Start with a one-pool allocation and predict its distortion before calculating ABC. Compare products on volume, batch size, complexity and support demand. A high-volume simple product often absorbs too much of a pool driven partly by setups or inspections, while a low-volume complex product absorbs too little. Write that prediction down so the calculated shift can be checked against the operational story.
In the ABC version, label the first-stage resource assignment and the second-stage activity assignment separately. For each pool, record the cost, selected driver, driver quantity and rate with units. Apply the rates to product consumption and reconcile all assignments to the original overhead total. If the total changes between systems, investigate scope or arithmetic before interpreting accuracy.
Classify activities as unit, batch, product-sustaining or facility-level and explain why a volume driver represents some levels better than others. Practise replacing a convenient correlated driver with a root-cause alternative, then discuss whether the improved data would alter pricing, process improvement, customer policy or capacity planning. Keep practical capacity visible.
Separate the cost of resources supplied from the activity cost used, and do not force unused capacity into product assignments if doing so would hide the capacity signal. Compare rates based on expected use with rates based on practical capacity and explain how falling demand can otherwise inflate product cost.
For implementation questions, make a benefits-and-burdens table covering distortion, data availability, maintenance effort, staff understanding and behavioural effects. More pools are not automatically better; they earn their place when materially different resource demands matter to a decision. Finally, convert the ABC result into a decision carefully.
Identify which activity resources would actually be released, when capacity can change and whether another object can use it. Add customer, quality and strategic effects before recommending a price change or discontinuation. In timed revision, finish with three checks: assignments reconcile, drivers have causal explanations, and allocated facility cost has not been mistaken for avoidable cash flow.
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