ACCT2002 Chap.6 Activity-Based Costing and Management
Activity-Based Costing and Management
Activity-based costing refines indirect-cost assignment when products or services consume support resources in different patterns. A broad plantwide rate can overcost simple high-volume output and undercost complex low-volume work because the allocation base does not represent the activities that drive cost.
ABC first assigns resource costs to activity pools, then assigns each pool to cost objects using a driver that reflects consumption. This chapter contrasts plantwide, departmental and activity rates, explains the course's four-part cost hierarchy, and connects costing accuracy to activity-based management.
More detail is not automatically better: a refined system should improve decisions enough to justify measurement, maintenance and behavioural costs.
What this chapter covers
- 01
Broad averaging, undercosting and overcosting
- 02
Plantwide and departmental overhead rates
- 03
Two-stage activity-based costing
- 04
The four-part cost hierarchy
- 05
Choosing activity cost drivers
- 06
Product and customer profitability
- 07
Activity-based management
- 08
Benefits and implementation costs
Expose cross-subsidisation with two activity pools
- 2Setup rate is $180,000 ÷ 120 = $1,500 per setup. Processing rate is $240,000 ÷ 30,000 = $8 per machine-hour.
- 3Product R receives 18 × $1,500 + 8,000 × $8 = $91,000, or $22.75 per unit.
- 3Product S receives 42 × $1,500 + 4,000 × $8 = $95,000, or $118.75 per unit.
- 2S's small batches consume many setups relative to volume. A machine-hour-only rate would hide that complexity and shift some setup cost toward R.
Key terms
- Broad averaging
- Use of an allocation approach that smooths unlike patterns of resource consumption into one average rate.
- Undercosting
- Assigning less cost to a cost object than the resources it consumes.
- Overcosting
- Assigning more cost to a cost object than the resources it consumes.
- Activity cost pool
- A grouping of indirect costs associated with a particular activity.
- Cost hierarchy
- Classification of activities by unit-level, batch-level, product-sustaining and facility-sustaining relationships.
- Activity driver
- A measurable factor used to assign activity-pool costs to cost objects.
- Activity-based management
- Using activity information to improve pricing, product mix, process design and resource use.
Activity-Based Costing and Management FAQ
How does ABC differ from a departmental system?
Departmental rates refine a plantwide rate by location or function. ABC can go further by separating several activities within a department when they have different drivers.
Which costs are hardest to assign causally?
Facility-sustaining costs often support the organisation as a whole and may not have a convincing product-level driver. An arbitrary allocation should be identified as such.
Does ABC change total overhead?
No. It changes how an existing total is assigned to cost objects. The value comes from different profitability and decision signals, not from creating or removing cost.
When is ABC worth implementing?
When indirect costs are significant, products differ in complexity or batch demands, current rates create disputed margins, and reliable driver data can be collected at a reasonable cost.
Exam move
Redraw every allocation as a two-stage map and annotate the causal claim. Compare the same products under one plantwide rate and under ABC, then identify which product was cross-subsidised. Memorise the cost hierarchy through examples rather than definitions.
Finish with a management action—redesign a batch process, reprice a complex product or remove a non-value-adding activity—while remembering that allocated facility cost may not disappear. Explain that distinction aloud for viva preparation.
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