ACCT90009 Chap.4 Activity-Based Costing and Cost Drivers

Activity-Based Costing and Cost Drivers

Standard canon anchored to Week 4. ABC assigns resources to activity pools and activities to cost objects.

Unit, batch, product and facility levels reveal why a single volume base can cross-subsidise complexity.

Detailed chapter study map

AskSia Library · ACCT90009 · Strategic Cost Management · University of Melbourne ABC FOUNDATIONS Week 4 · standard canon STANDARD CANON Activities explain why overhead exists From resource spending to activity demand and cost objects The official Week 4 topic is Activity Based Costing.

This chapter presents standard accounting canon rather than claiming the current lecturer’s exact pool list or assessment emphasis. ABC asks what work consumes resources and what products, services or customers demand that work. It replaces one broad allocation with multiple causal stories. The organisation’s total cost does not change; the visibility of cross-subsidy and unused capacity can.

ABC two-stage assignment Resources are first associated with activities, then activity costs are assigned

to objects using drivers that represent demand for work. Original schematic. Two assignment stages Resource costs are associated with activities using resource drivers or direct tracing. Activity pools are then assigned to cost objects using activity drivers. Each stage needs an economic explanation.

A precise activity rate built from a badly defined pool still creates misleading object costs. ABC is a decision system The objective is not maximum allocation detail. Managers use the model to redesign work, change product or customer policy, price complexity and expose capacity. If no decision improves, added measurement may be waste.

Treat the model as a hypothesis about resource consumption and revise it when processes change. i Purpose before pools

Name the decision and likely distortion first. Then design the smallest set of pools and drivers able to distinguish alternatives. Starting with every account produces complexity without necessarily producing relevance. !

ABC does not make every assigned cost avoidable A cost can be causally associated with an activity yet remain committed for the decision horizon. Use ABC to understand consumption, then run a separate relevance and capacity-release test. ABC changes the map of resource demand, not the total resources already spent.

ABC principle {PG} · asksia.ai/explore AskSia Library · ACCT90009 · Strategic Cost Management · University of Melbourne ACTIVITY DICTIONARY Activity dictionary Define work before assigning dollars Verb–noun activities, boundaries, outputs and capacity An activity

dictionary names the work represented by each pool.

Useful names combine a verb and object — schedule production, inspect batches, process orders, support customers — because action can be improved. Vague pools such as “administration” combine unrelated causes and make rates difficult to interpret. Dictionary field Question Example Activity What work is performed? Schedule production runs Trigger Why does work begin? A new batch is authorised Output What is completed?

One scheduled batch Resources What capacity is consumed? Planner time and system support Driver What measures demand? Number of batches, adjusted for complexity Capacity How much work can resources supply? Practical batch-planning capacity Keep pools homogeneous A pool is homogeneous when one driver reasonably explains

its cost.

Combining inspection and engineering changes under “quality” may be convenient but weak: inspections follow batches, while engineering changes follow product complexity. Split only when the difference is material to decisions. Distinguish value and necessity An activity can be non-value-adding to the customer yet currently necessary for compliance or control. The label should trigger redesign, not careless deletion.

Ask whether the trigger can be prevented, the work simplified, frequency reduced or output improved without transferring risk. P4.1 Activity definition Answer included Is “quality” a strong activity name? Answer. Usually not. Separate inspect batches, investigate defects and redesign process because their triggers, outputs and drivers differ. P4.2 Pool split Answer included When should two support

tasks stay together?

Answer. When they share a plausible driver and separating them would not materially improve the targeted decision relative to measurement cost.

{PG} · asksia.ai/explore AskSia Library · ACCT90009 · Strategic Cost Management · University of Melbourne DRIVER DESIGN Driver design Transaction, duration and intensity Choose the lowest-cost driver that preserves decision relevance A transaction driver counts events, a duration driver measures time, and an intensity driver traces actual resources. Counts are cheap and assume events are similar.

Duration recognises complexity. Intensity is most precise and expensive. The right level depends on variation within the activity and the value of the decision. ABC RATE [formula shown in the full chapter] [formula shown in the full chapter] Causality and controllability A driver should represent

demand for activity, but performance use adds a second requirement: the measured party should be able to influence it.

Number of purchase orders may cause procurement work, while a production manager may not control supplier minimum quantities. Separate costing from responsibility when needed. Avoid reverse incentives Charging quality support by inspection count may encourage teams to reduce inspections without preventing defects. Charging by defects may discourage reporting. No driver is behaviour-free.

Pair cost visibility with outcome measures and governance that rewards genuine improvement rather than data suppression.

Driver Strength Risk Number of setups Simple where setups are similar Ignores long or complex setups Setup hours Captures duration Still ignores specialist intensity Actual setup resources High

precision Expensive to collect Orders Good transaction signal Order lines or complexity may differ Customer contacts Visible service demand May penalise reporting or prevention ✓ Test the model on opposites Cost one high-volume simple object and one low-volume complex object.

If the driver cannot explain

What this chapter covers

• 01

  Two-stage assignment

• 02

  Activity dictionary and hierarchy

• 03

  Driver design

• 04

  Unused capacity and implementation

AskSia-authored practice weighting (not an official mark scheme): Two activity pools

Key terms

Activity pool

Cost of a homogeneous activity.

Activity driver

Measure of demand for activity.

Activity-Based Costing and Cost Drivers FAQ

Exam move

Design the smallest causal model that changes a decision. Reconcile pools and explain the operational activity behind every cost movement.

Working through Activity-Based Costing and Cost Drivers in ACCT90009? Sia is AskSia’s AI Accounting tutor — ask any ACCT90009 Activity-Based Costing and Cost Drivers question and get a clear, step-by-step explanation grounded in how ACCT90009 is taught and assessed. Read this chapter free, then take your hardest questions to Sia.