Why is "Confusing the cost pool with the cost driver" a common mistake in Activity Based Costing?

Why it happens: Both relate to an activity. How to avoid it: Cost POOL = the overhead total of an activity; cost DRIVER = the activity measure that causes it. Source: 9706 Examiner Reports

Why is "Dividing the pool by the wrong volume" a common mistake in Activity Based Costing?

Why it happens: Using a single product's usage instead of the total. How to avoid it: Cost driver rate = pool ÷ TOTAL driver volume (across all products). Source: 9706 Examiner Reports

Why is "Using one overhead rate for everything" a common mistake in Activity Based Costing?

Why it happens: Reverting to absorption costing. How to avoid it: ABC uses a SEPARATE rate for EACH cost pool; charge products from each pool. Source: 9706 Examiner Reports

Why is "Using a volume driver for a non-volume activity" a common mistake in Activity Based Costing?

Why it happens: Defaulting to units/hours. How to avoid it: Choose the driver that genuinely CAUSES the cost (set-ups, orders) — otherwise ABC adds no accuracy. Source: 9706 Examiner Reports

Why is "Quoting overhead as the full cost" a common mistake in Activity Based Costing?

Why it happens: Forgetting the direct costs. How to avoid it: Full cost = direct costs + ABC overhead; add the direct materials and labour. Source: 9706 Examiner Reports

Why is "Charging from only one pool" a common mistake in Activity Based Costing?

Why it happens: Stopping after one activity. How to avoid it: Charge overhead from EVERY relevant cost pool and SUM for the product's total overhead. Source: 9706 Examiner Reports

Cambridge International A Levels Accounting (9706)

Activity Based Costing

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Detailed Study Notes

Detailed notes on Activity based costing (ABC) for Cambridge International A Levels Accounting, covering key concepts, explanations, examples, and exam-focused revision points.

Activity Based Costing (ABC) — Cambridge AS & A Level Accounting 9706 Study Notes (2026-2028)

A more accurate way to share overheads. Learn how activity based costing (ABC) groups overheads into cost pools, identifies the cost driver of each, calculates a cost driver rate, and charges overheads to products based on the activities they actually cause.

At a glance

ABC shares overheads using the activities that cause them, not a single volume-based rate.
Cost pool: overheads grouped by activity (e.g. machine set-ups, ordering, quality inspection).
Cost driver: the factor that causes the cost of an activity (e.g. number of set-ups, orders, inspections).
Cost driver rate = cost pool ÷ total cost driver volume.
Overhead charged to a product = cost driver rate × that product's use of the driver.
ABC gives more accurate product costs where overheads are complex and not volume-driven.
It is the four-step method: pools → drivers → rates → charge to products.

What you’ll learn

Mapped to the Cambridge International A Level 9706 syllabus (2026-2028).

2.2.4 — Understand the principles of activity based costing.
2.2.4 — Identify cost pools and cost drivers and calculate cost driver rates.
2.2.4 — Charge overheads to products using ABC.

The idea behind ABC

Charge overheads by the activities that cause them, not just by volume.

Traditional absorption costing shares overheads using a single, volume-based rate (e.g. per machine hour or labour hour). This works when overheads are mainly volume-driven, but many modern overheads are not — they are caused by activities such as machine set-ups, ordering, materials handling and quality inspection, which depend on the number of times an activity happens, not the number of units made.

Activity based costing (ABC) charges overheads to products based on the activities each product actually causes. The principle: a product that triggers more set-ups, orders or inspections should bear more of those overheads, even if it is a low-volume product. This gives more accurate product costs, especially where there is a wide range of products with different complexities.

Absorption costing uses a single volume-based rate.
Many overheads are activity-driven, not volume-driven.
ABC charges overheads by the activities each product causes.
More accurate where products differ in complexity.

See the full worked example for activity based costing →

Cost pools and cost drivers

Group overheads into pools; find the driver that causes each.

Two key terms:

Cost pool — overheads grouped together by activity. For example, all the costs of setting up machines form the 'set-up' cost pool; all the costs of processing orders form the 'ordering' cost pool.
Cost driver — the factor that causes the cost of an activity. It is what makes the cost pool go up or down:

Activity (cost pool)	Cost driver
Machine set-ups	Number of set-ups
Ordering materials	Number of orders
Materials handling	Number of material movements
Quality inspection	Number of inspections
Machining	Machine hours

So ABC asks, for each activity: what causes this cost? — and uses that driver to share the pool. Choosing the right driver is the heart of ABC; a poorly chosen driver gives no more accuracy than absorption costing.

Cost pool = overheads grouped by activity.
Cost driver = the factor that causes an activity's cost.
Set-ups → number of set-ups; ordering → number of orders, etc.
Choosing the right driver is the key to ABC's accuracy.

See the full worked example for activity based costing →

The cost driver rate and charging products

Rate = pool ÷ total driver volume; charge by each product's use.

Once each cost pool and its cost driver are identified, ABC works in two steps:

Step 1 — calculate the cost driver rate for each pool:

$\text{Cost driver rate} = \frac{\text{Cost pool}}{\text{Total volume of the cost driver}}$

Example. Set-up cost pool $60,000; total set-ups 300 → rate = $200 per set-up.

Step 2 — charge overhead to each product by how much of the driver it uses:

$\text{Overhead charged} = \text{Cost driver rate} \times \text{product's use of the driver}$

Example. A product needing 20 set-ups is charged 200 × 20 = $4,000 of set-up overhead.

Do this for every cost pool and add the amounts to get the product's total overhead under ABC. Adding the direct costs gives the full cost per unit — the same idea as absorption costing, but with overheads shared activity by activity.

Cost driver rate = cost pool ÷ total driver volume.
Overhead charged = rate × product's use of the driver.
Repeat for every cost pool and total the overheads.
Add direct costs for the full cost per unit.

See the full worked example for activity based costing →

The four steps of ABC

Pools → drivers → rates → charge to products.

The full ABC method is four steps:

Identify the activities and group their overheads into cost pools.
Identify the cost driver for each pool (what causes the cost).
Calculate the cost driver rate = cost pool ÷ total driver volume.
Charge overheads to products = rate × each product's use of the driver, then add direct costs for the full cost.

Compared with absorption costing, ABC replaces the single overhead rate with multiple activity rates — one per cost pool. The result is a product cost that reflects the real demands each product places on the business's activities.

So ABC is more detailed and more accurate, but also more complex and costly to operate (covered in the next subtopics). The mechanics, though, are just 'rate × usage' applied activity by activity.

Step 1: group overheads into cost pools by activity.
Step 2: identify each pool's cost driver.
Step 3: cost driver rate = pool ÷ total driver volume.
Step 4: charge products = rate × usage; add direct costs.

Quick recap

ABC shares overheads by the activities that cause them, not a single volume-based rate.
Cost pool = overheads grouped by activity; cost driver = the factor causing the cost.
Cost driver rate = cost pool ÷ total driver volume.
Overhead charged to a product = rate × product's use of the driver.
Four steps: pools → drivers → rates → charge to products (+ direct costs).
ABC gives more accurate costs where overheads are complex and not volume-driven.

Memorise this

Verbatim phrases and definitions Cambridge mark schemes credit.

Cost driver rate = cost pool ÷ total cost driver volume.
Overhead charged = cost driver rate × product's use of the driver.
Four steps: cost pools → cost drivers → driver rates → charge to products.
Cost pool = overhead grouped by activity; cost driver = what causes the cost.

How it’s examined

Tested on Paper 4 (A Level): calculate cost driver rates and charge overheads to products using ABC, often to find a full cost per unit (commonly [6-12] marks). Examiner reports note candidates confusing cost pools with cost drivers and dividing by the wrong volume.

Sources: Cambridge International AS & A Level Accounting 9706 syllabus (2026-2028); 9706 Paper 4 past papers & mark schemes, 2022-2024; 9706 Examiner Reports, 2022-2024. Last reviewed 2026-06-19.

Take this whole topic with you

Step-by-step worked examples — Activity Based Costing

Step-by-step solutions to past-paper-style questions on activity based costing, written exactly the way a tutor would explain them at the board.

Question type:

1Why ABC? (4 marks)
Getting startedWord problem• 9706 Paper 4 style• ABC, AO1
Question
Explain how activity based costing shares overheads differently from traditional absorption costing. (4 marks)
Step-by-step solution
1. Step 1
  Absorption costing uses a single, volume-based rate (e.g. per machine/labour hour).
2. Step 2
  ABC groups overheads into cost pools by activity.
3. Step 3
  It charges each product by the activities it actually causes (cost drivers).
4. Step 4
  So products causing more set-ups/orders/inspections bear more overhead, even if low-volume.
Answer
ABC uses multiple activity-based rates (cost drivers); absorption uses one volume-based rate.
Examiner tip
ABC links overhead to the activities that cause it.
2Pool or driver? (4 marks)
Getting startedIdentify & classify• cost driver, AO1
Question
For each activity, state a suitable cost driver: (a) machine set-ups; (b) processing purchase orders; (c) quality inspections; (d) machining. (4 marks)
Step-by-step solution
1. Step 1
  (a) Machine set-ups → number of set-ups.
2. Step 2
  (b) Processing orders → number of orders.
3. Step 3
  (c) Quality inspections → number of inspections.
4. Step 4
  (d) Machining → machine hours.
Answer
(a) set-ups; (b) orders; (c) inspections; (d) machine hours.
Examiner tip
The cost driver is what causes the activity's cost.
3Cost driver rate (3 marks)
Getting startedDirect calculation• driver rate, AO2
Question
The set-up cost pool is $90,000 and there are 450 set-ups in total. Calculate the cost driver rate per set-up. (3 marks)
Step-by-step solution
1. Step 1
  Cost driver rate = cost pool ÷ total driver volume.
2. Step 2
  = 90,000 ÷ 450.
3. Step 3
  = $200 per set-up.
Answer
$200 per set-up.
Examiner tip
Divide the pool by the TOTAL number of driver events.
4Charge overhead to a product (4 marks)
Building confidenceMulti-step problem• charging, AO2
Question
The set-up rate is $200 per set-up. Product A requires 30 set-ups. Calculate the set-up overhead charged to Product A. (4 marks)
Step-by-step solution
1. Step 1
  Overhead charged = rate × product's use of the driver.
2. Step 2
  = 200 × 30.
3. Step 3
  = $6,000.
Answer
$6,000.
Examiner tip
Multiply the rate by the product's usage of that driver.
5Two cost pools (5 marks)
Building confidenceMulti-step problem• ABC, AO2
Question
Set-up rate $200/set-up; ordering rate$ 50/order. Product B uses 15 set-ups and 80 orders. Calculate the total overhead charged to Product B. (5 marks)
Step-by-step solution
1. Step 1
  Set-up overhead = 200 × 15 = $3,000.
2. Step 2
  Ordering overhead = 50 × 80 = $4,000.
3. Step 3
  Total overhead = 3,000 + 4,000 = $7,000.
Answer
$7,000.
Examiner tip
Charge from each pool by usage, then sum.
6Overhead per unit (4 marks)
Building confidenceMulti-step problem• ABC, AO2
Question
Product C is charged total overhead of $24,000 under ABC and 4,000 units are made. Calculate the overhead per unit. (4 marks)
Step-by-step solution
1. Step 1
  Overhead per unit = total overhead charged ÷ units made.
2. Step 2
  = 24,000 ÷ 4,000.
3. Step 3
  = $6 per unit.
Answer
$6 per unit.
Examiner tip
Divide the product's total ABC overhead by its output.
7Full cost per unit under ABC (6 marks)
StretchMulti-step problem• full cost, AO2
Question
Product D: direct materials $10/unit, direct labour$ 8/unit. Total ABC overhead $36,000 for 6,000 units. Calculate the full cost per unit. (6 marks)
Step-by-step solution
1. Step 1
  Overhead per unit = 36,000 ÷ 6,000 = $6.
2. Step 2
  Direct cost per unit = 10 + 8 = $18.
3. Step 3
  Full cost per unit = 18 + 6 = $24.
Answer
Full cost per unit = $24.
Examiner tip
Add the ABC overhead per unit to the direct costs.
8Three cost pools (6 marks)
StretchMulti-step problem• ABC, AO2
Question
Rates: set-ups $200; orders$ 50; inspections $80. Product E uses 10 set-ups, 60 orders and 25 inspections. Calculate the total overhead charged to Product E. (6 marks)
Step-by-step solution
1. Step 1
  Set-ups = 200 × 10 = $2,000.
2. Step 2
  Orders = 50 × 60 = $3,000.
3. Step 3
  Inspections = 80 × 25 = $2,000.
4. Step 4
  Total = 2,000 + 3,000 + 2,000 = $7,000.
Answer
$7,000.
Examiner tip
Apply each pool's rate to the product's usage and total them.
9Choosing the right driver (4 marks)
StretchWord problem• cost driver, AO3
Question
Explain why choosing an appropriate cost driver is essential for ABC to be more accurate than absorption costing. (4 marks)
Step-by-step solution
1. Step 1
  The cost driver determines how each pool is shared between products.
2. Step 2
  A driver that genuinely causes the cost shares it fairly to the products that trigger it.
3. Step 3
  A poorly chosen driver (e.g. volume) shares the same as absorption costing — no extra accuracy.
4. Step 4
  So accurate driver choice is what gives ABC its improved accuracy.
Answer
The driver shares each pool; only a genuine cause-and-effect driver gives ABC's accuracy advantage.
Examiner tip
ABC is only as good as the cost drivers chosen.
10The four steps (4 marks)
StretchWord problem• ABC, AO1
Question
State the four steps of activity based costing in order. (4 marks)
Step-by-step solution
1. Step 1
  
  Group overheads into cost pools by activity.
2. Step 2
  
  Identify the cost driver for each pool.
3. Step 3
  
  Calculate the cost driver rate (pool ÷ total driver volume).
4. Step 4
  
  Charge overheads to products (rate × usage); add direct costs for full cost.
Answer
Cost pools → cost drivers → driver rates → charge to products.
Examiner tip
Learn the four-step sequence.

Model Answers — Activity Based Costing

High-scoring sample answers for activity based costing on the Cambridge IGCSE paper, with examiner-style notes mapping each response to the mark scheme and assessment objectives.

Question 1
9706 Paper 4 style4 marks
Q (4 marks). Explain the meaning of the terms 'cost pool' and 'cost driver' in activity based costing, giving an example of each.
Model answer
A cost pool is the overheads of an activity grouped together — for example, all the costs of setting up machines form the 'set-up' cost pool. A cost driver is the factor that causes the cost of that activity — for example, the number of set-ups. The cost driver is used to share the cost pool between products according to how much of the activity each product causes.
Why this scores
Marking (point-based, 4). Cost pool + example (2); cost driver + example (2).
Question 2
9706 Paper 4 style3 marks
Q (3 marks). The ordering cost pool is $48,000 and there are 600 orders in total. Calculate the cost driver rate per order.
Model answer
Cost driver rate = cost pool ÷ total orders = 48,000 ÷ 600 = $80 per order.
Why this scores
Marking (point-based, 3). Method (1); $80 (2).
Question 3
9706 Paper 4 style4 marks
Q (4 marks). Suggest a suitable cost driver for each activity: (a) machine set-ups; (b) materials handling; (c) customer order processing; (d) quality control inspection.
Model answer
(a) Machine set-ups → number of set-ups. (b) Materials handling → number of material movements (or weight of materials). (c) Customer order processing → number of orders. (d) Quality control inspection → number of inspections.
Why this scores
Marking (point-based, 4). 1 mark each appropriate driver.
Question 4
9706 Paper 4 style5 marks
Q (5 marks). Cost driver rates are: set-ups $250 per set-up; inspections$ 60 per inspection. Product X requires 12 set-ups and 90 inspections. Calculate the total overhead charged to Product X under ABC.
Model answer
Set-up overhead = 250 × 12 = $3,000. Inspection overhead = 60 × 90 = $5,400. Total overhead = 3,000 + 5,400 = $8,400.
Why this scores
Marking (point-based, 5). Set-ups $3,000 (2); inspections$ 5,400 (2); total $8,400 (1).
Question 5
9706 Paper 4 style8 marks
Q (8 marks). A company has two cost pools: set-ups ( $120,000, 600 set-ups) and ordering ($ 90,000, 1,500 orders). Product Y uses 40 set-ups and 200 orders and makes 5,000 units, with direct costs of $16 per unit. Calculate the cost driver rates, the total overhead charged to Y, the overhead per unit and the full cost per unit.
Model answer
Rates: set-ups = 120,000 ÷ 600 = $200 per set-up; ordering = 90,000 ÷ 1,500 = $60 per order. Overhead charged to Y: set-ups 200 × 40 = 8,000; ordering 60 × 200 = 12,000; total = $20,000. Overhead per unit = 20,000 ÷ 5,000 = $4. Full cost per unit = direct 16 + overhead 4 = $20.
Why this scores
Marking (point-based, 8). Rates $200/$ 60 (2); overhead $20,000 (3); per unit$ 4 (1.5); full cost $20 (1.5).
Question 6
9706 Paper 4 style4 marks
Q (4 marks). Describe the four steps involved in applying activity based costing.
Model answer
1. Identify the main activities and group their overheads into cost pools. 2. Identify the cost driver for each pool (the factor that causes its cost). 3. Calculate the cost driver rate = cost pool ÷ total cost driver volume. 4. Charge the overheads to products by multiplying each rate by the product's use of the driver, and add the direct costs to obtain the full cost.
Why this scores
Marking (point-based, 4). 1 mark each step in order.
Question 7
9706 Paper 4 style6 marks
Q (6 marks). Explain why the choice of cost driver is critical to the accuracy of activity based costing, using an example to support your answer.
Model answer
In ABC, the cost driver determines how each cost pool is shared between products, so it directly affects the product costs calculated. For ABC to be more accurate than absorption costing, the driver must reflect a genuine cause-and-effect relationship — the factor that actually makes the cost rise or fall.

For example, the cost of machine set-ups is driven by the number of set-ups, not by the number of units produced. A low-volume, complex product that needs many set-ups should bear a large share of set-up costs. If the driver chosen were units (a volume measure), the high-volume product would absorb most of the set-up cost and the complex low-volume product would be under-costed — exactly the distortion ABC is meant to correct, so ABC would add no accuracy.

Therefore, choosing a driver that genuinely causes each activity's cost is what gives ABC its improved accuracy; a poorly chosen (e.g. volume-based) driver produces results no better than traditional absorption costing.
Why this scores
Marking (point-based, 6). Driver shares the pool / affects costs (~2); cause-and-effect needed (~2); worked example of distortion (~2).
Question 8
9706 Paper 4 style4 marks
Q (4 marks). Explain how activity based costing differs from traditional absorption costing in the way it charges overheads to products.
Model answer
Traditional absorption costing charges overheads to products using a single, volume-based overhead absorption rate (such as per machine hour or labour hour), assuming overheads rise with volume. Activity based costing instead groups overheads into cost pools by activity, identifies the cost driver that causes each, and charges overheads to products according to how much of each activity (driver) the product actually uses. So ABC uses several activity-based rates rather than one volume-based rate, giving costs that reflect the real demands each product places on the business's activities.
Why this scores
Marking (point-based, 4). Absorption = single volume rate (2); ABC = pools/drivers, multiple activity rates (2).
Question 9
9706 Paper 4 style6 marks
Q (6 marks). A factory has three cost pools with rates: set-ups $300 per set-up; orders$ 40 per order; inspections $25 per inspection. Product Z uses 8 set-ups, 150 orders and 320 inspections, and makes 2,000 units. Calculate the total overhead charged to Z and the overhead per unit.
Model answer
Set-ups = 300 × 8 = 2,400. Orders = 40 × 150 = 6,000. Inspections = 25 × 320 = 8,000. Total overhead = 2,400 + 6,000 + 8,000 = $16,400. Overhead per unit = 16,400 ÷ 2,000 = $8.20.
Why this scores
Marking (point-based, 6). Three pool charges (3); total $16,400 (2); per unit$ 8.20 (1).
Question 10
9706 Paper 4 style3 marks
Q (3 marks). Product W is charged $45,000 of overhead under ABC and produces 9,000 units. Calculate the overhead cost per unit.
Model answer
Overhead per unit = 45,000 ÷ 9,000 = $5 per unit.
Why this scores
Marking (point-based, 3). Method (1); $5 (2).

Key Formulae — Activity Based Costing

The formulae you need to memorise for activity based costing on the Cambridge IGCSE paper, with every variable defined in plain English and a note on when to use it.

Cost driver rate
$Cost\ driver\ rate = \frac{Cost\ pool}{Total\ cost\ driver\ volume}$
$Cost pool$
overheads grouped for an activity
$Total cost driver volume$
total number of driver events (set-ups, orders, etc.)
When to use
To find the overhead rate per unit of a cost driver.
Example
90,000 ÷ 450 = $200 per set-up.
Overhead charged to a product
$Overhead\ charged = Cost\ driver\ rate \times Product's\ use\ of\ the\ driver$
$Cost driver rate$
the rate per driver event
$Product's use$
the number of driver events that product causes
When to use
To charge each cost pool's overhead to a product.
Example
200 × 30 = $6,000.

Key Definitions and Keywords — Activity Based Costing

Definitions to memorise and the exact keywords mark schemes credit for activity based costing answers — sharpened from recent examiner reports for the 2026 Cambridge IGCSE sitting.

Activity based costing (ABC)
Examiner keyword
A costing method that charges overheads to products using the activities (cost drivers) that cause them.
Cost pool
Examiner keyword
Overheads grouped together by activity (e.g. set-up costs, ordering costs).
Cost driver
Examiner keyword
The factor that causes the cost of an activity (e.g. number of set-ups, orders, inspections).
Cost driver rate
Examiner keyword
Cost pool ÷ total cost driver volume; the overhead rate per driver event.
Activity
Examiner keyword
A task or process that consumes resources (e.g. setting up machines, inspecting goods).
Absorption costing (contrast)
Traditional method using a single volume-based overhead rate, rather than activity-based rates.

Common Mistakes and Misconceptions — Activity Based Costing

The traps other students keep falling into on activity based costing questions — taken from recent Cambridge IGCSE examiner reports and mark schemes — and how to avoid them.

✕Confusing the cost pool with the cost driver
9706 Examiner Reports
Why it happens
Both relate to an activity.
How to avoid it
Cost POOL = the overhead total of an activity; cost DRIVER = the activity measure that causes it.
✕Dividing the pool by the wrong volume
9706 Examiner Reports
Why it happens
Using a single product's usage instead of the total.
How to avoid it
Cost driver rate = pool ÷ TOTAL driver volume (across all products).
✕Using one overhead rate for everything
9706 Examiner Reports
Why it happens
Reverting to absorption costing.
How to avoid it
ABC uses a SEPARATE rate for EACH cost pool; charge products from each pool.
✕Using a volume driver for a non-volume activity
9706 Examiner Reports
Why it happens
Defaulting to units/hours.
How to avoid it
Choose the driver that genuinely CAUSES the cost (set-ups, orders) — otherwise ABC adds no accuracy.
✕Quoting overhead as the full cost
9706 Examiner Reports
Why it happens
Forgetting the direct costs.
How to avoid it
Full cost = direct costs + ABC overhead; add the direct materials and labour.
✕Charging from only one pool
9706 Examiner Reports
Why it happens
Stopping after one activity.
How to avoid it
Charge overhead from EVERY relevant cost pool and SUM for the product's total overhead.

Activity Based Costing

Detailed Study Notes

At a glance

What you’ll learn

Quick recap

Memorise this

How it’s examined

Take this whole topic with you

1Why ABC? (4 marks)

2Pool or driver? (4 marks)

3Cost driver rate (3 marks)

4Charge overhead to a product (4 marks)

5Two cost pools (5 marks)

6Overhead per unit (4 marks)

7Full cost per unit under ABC (6 marks)

8Three cost pools (6 marks)

9Choosing the right driver (4 marks)

10The four steps (4 marks)

Cost driver rate

Overhead charged to a product

Activity based costing (ABC)

Cost pool

Cost driver

Cost driver rate

Activity

Absorption costing (contrast)

✕Confusing the cost pool with the cost driver

✕Dividing the pool by the wrong volume

✕Using one overhead rate for everything

✕Using a volume driver for a non-volume activity

✕Quoting overhead as the full cost

✕Charging from only one pool