What it means
Traditional cost accounting answers the question "where was the money spent?" by department. That is useful for budgets and accountability, but it does not answer "why was it spent?" or "what did we get for it?".
A department's cost is the sum of many activities, some valuable and some not, and the total hides which is which. Activity accounting breaks each department's cost into the activities its people perform, using time studies, interviews or estimates, and assigns a cost to each.
The result is a list of activities with their costs, often a revelation in itself: organisations routinely discover that they spend more on handling exceptions, corrections and rework than on the core work those exceptions interrupt. The second step traces activity costs to cost objects: products, services, customers, projects or channels.
Each activity has a driver, a measure of how much of it a cost object consumes: number of orders, number of set-ups, number of customer calls, hours of engineering time. Multiplying the activity's cost per driver unit by the units each product or customer consumes gives a cost assignment based on cause rather than on an arbitrary allocation.
This is activity-based costing, and its use for pricing and profitability decisions is described under that term. The management use of the information, activity-based management, is where the value lies.
Activities can be classified as value-adding (things customers pay for) or non-value-adding (inspections, rework, waiting, duplicated approvals), and the cost of the second category is a direct target for process improvement. Activity costs can be benchmarked against other organisations or other sites.
Capacity can be analysed: if order processing costs $50 per order and the team processes 8,000 orders a year but could handle 12,000, the cost of unused capacity is visible and can be addressed by winning volume or reducing resources. The approach is expensive to implement fully and is usually applied selectively: to the activities that consume the most overhead, to the decisions where traditional costing is known to mislead, or as a periodic study rather than a continuous system.
Its lasting contribution is a way of thinking: costs are caused by activities, activities are caused by decisions, and managing costs means managing the decisions.
In practice
Real-world examples.
Example
A hospital analyses its outpatient clinic and finds that patient check-in, an activity costing $18 per visit, could be halved with online pre-registration.
Example
An insurer traces claims-handling cost by activity and discovers that 40% is spent on requesting missing information from claimants, prompting a redesign of the claim form.
Example
A logistics company assigns warehouse activity costs to customers by pallets handled, orders picked and returns processed, and reprices its three least profitable accounts.
Think of it
“Activity accounting traces costs to the activities that cause them-understanding what drives costs.
Formula
Calculation
Activity Cost = Sum of resource costs assigned to the activity (staff time, systems, space, supplies)
Cost per Driver Unit = Activity Cost / Total Driver Units
Cost assigned to a cost object = Sum over activities of (Cost per Driver Unit x Driver Units consumed)
Cost of Unused Capacity = Cost per Driver Unit at practical capacity x (Practical Capacity minus Actual Driver Units)
Worked example. A customer service department costs $720,000 a year (12 staff, systems and space). Interviews and time logs show the staff's time splits: answering product enquiries 35%; processing returns 25%; correcting order errors 20%; handling complaints 15%; training and administration 5%.
- Product enquiries: $252,000 for 42,000 enquiries = $6.00 each
- Returns: $180,000 for 9,000 returns = $20.00 each
- Order error corrections: $144,000 for 4,800 corrections = $30.00 each
- Complaints: $108,000 for 2,700 complaints = $40.00 each
- Training and admin: $36,000 (not traced to cost objects)
Assignment to two customer segments: retail chains generate 12,000 enquiries, 4,000 returns, 3,000 error corrections and 1,500 complaints; independent shops generate the rest.
- Retail chains: 12,000 x $6 + 4,000 x $20 + 3,000 x $30 + 1,500 x $40 = $72,000 + $80,000 + $90,000 + $60,000 = $302,000
- Independent shops: 30,000 x $6 + 5,000 x $20 + 1,800 x $30 + 1,200 x $40 = $180,000 + $100,000 + $54,000 + $48,000 = $382,000
Retail chains are 30% of customers by number but 44% of service cost, and $252,000 of the department's total ($144,000 errors + $108,000 complaints) is spent on non-value-adding activity that better order processes could eliminate.Case study
Seen in the real world.
An engineering firm with 200 staff believed its costs were well controlled because every department was within budget. An activity study across the design, procurement and project management departments produced a different picture. Of $9 million of combined cost, $2.1 million went on activities the study classed as non-value-adding: re-issuing drawings after late client changes, chasing suppliers, re-planning projects after scope creep, and internal approvals that added three signatures to every purchase over $500.
None of this was visible in the departmental budgets, because the people doing it were the same people doing the valuable work. The firm introduced change control on client projects with a fee for late changes, cut the approval chain to one signature below $5,000, and moved supplier chasing to an automated system. Eighteen months later the same departments cost $7.6 million on 10% more project revenue, and the firm's bid pricing, now based on activity costs, won a higher share of the projects it wanted and fewer of the ones that lost money.
Watch out
Common mistakes.
- Building an activity model so detailed that maintaining it costs more than the decisions it improves. Focus on the activities that consume most cost.
- Assigning every cost to a product or customer. Some costs, such as general management, are genuinely not caused by any particular cost object and should be left unassigned.
- Doing the study and filing it. The value is in the management action on non-value-adding activities and unprofitable cost objects.
Questions
People also ask.
What is the difference between activity accounting and activity-based costing?
Activity accounting is the broader practice of tracking costs by activity. Activity-based costing is its application to assigning costs to products and customers. Activity-based management is the use of the information to improve processes.
How are activity costs measured?
Through interviews, time logs, system data and estimates of how staff time and other resources are consumed by each activity. Time-driven approaches estimate the time each activity takes and the cost per minute of capacity.
Is activity accounting used in financial statements?
No. It is a management accounting tool. Statutory accounts use simpler cost classifications.
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