Cost Accounting · Introduction to Cost Accounting

Cost Concepts and Classification of Costs for CMA Inter

Updated 10 October 2026 · Fact-checked

Classification of costs means grouping costs by a common feature so they can be recorded, controlled and used for decisions. You classify by nature, function, behaviour, controllability and relevance. To solve questions, identify the cost object, then tag each cost on the basis the question asks for.

Understand Cost Concepts and Classification of Costs

A cost is the value of resources used to get something. In cost accounting, you always ask: cost of what? The answer is the cost object. A cost object is anything for which you want to measure cost. Examples: a product, a job, a department, a customer, a delivery route or a project.

A cost unit is the unit of product or service in which cost is expressed. Examples: per tonne of steel, per kWh of electricity, per passenger-km, per bed-day in a hospital. A cost centre is a location, person or item of equipment for which costs are collected. Examples: a machining department, a canteen, a delivery van. In short, a cost unit is what you measure the cost of, and a cost centre is where you collect the cost.

Costs are classified in several ways, and one cost can sit in many classifications at once. By nature: material, labour and expenses. By function: production, administration, selling and distribution, and research and development. By traceability: direct costs can be traced to a cost object economically; indirect costs (overheads) cannot and are shared through allocation and apportionment.

By behaviour: a fixed cost stays constant in total within the relevant range of activity, so cost per unit falls as output rises. A variable cost changes in total in proportion to activity, while cost per unit stays constant. A semi-variable cost has a fixed part and a variable part, such as a telephone bill with rent plus charges per call. A step cost stays fixed over a range and then jumps.

By controllability: a controllable cost can be influenced by a given manager at a given level within a given period; an uncontrollable cost cannot. The same cost can be controllable for one manager and uncontrollable for another. By relevance to decisions: relevant costs are future, differ between alternatives and are avoidable. Sunk (past) costs are irrelevant. Opportunity cost is the benefit lost by choosing one option over another, and it is relevant. Committed costs arise from past commitments and are hard to avoid in the short run.

Key rules to remember

Total cost: Total cost = Fixed cost + Variable cost; Fixed cost holds constant in total within the relevant range.
Semi-variable cost: Total cost = Fixed element + (Variable rate per unit × Activity); Use it to split a mixed cost into its two parts.
Variable cost per unit by high-low method: Variable cost per unit = (Cost at high activity − Cost at low activity) ÷ (High activity − Low activity); Fixed element = Total cost at either level − Variable rate × activity at that level.
Fixed cost per unit: Fixed cost per unit = Total fixed cost ÷ Units produced; This falls as output rises; total fixed cost does not change.
Prime cost: Prime cost = Direct material + Direct labour + Direct expenses; Direct costs are those traceable to the cost unit.
Relevance rule: Relevant cost = future, avoidable cash cost that differs between alternatives; Sunk costs and committed costs already incurred are ignored.

How to solve Cost Concepts and Classification of Costs questions

Use this method for any question that asks you to identify, classify or explain costs.

1Read the question and find the cost object or cost unit. Note what the question asks you to classify by: nature, function, behaviour, controllability or relevance.
2List each cost item given in the question.
3Tag each item on the basis asked. For behaviour, ask: if output doubles, what happens to this cost in total?
4For traceability, ask: can this cost be traced to the cost unit economically? If yes, direct; if no, indirect.
5For mixed (semi-variable) costs, split them using the high-low method or the given data before classifying.
6For controllability, name the manager and the time period. Do not label a cost controllable in general.
7For decision questions, discard sunk and committed costs, and keep future costs that differ between options.
8Present the answer as a short table or a labelled list, with one-line reasons for non-obvious items.

Quickest way: Three-question tag test

When to use it: Use it in Section A MCQs and in short written parts when you must tag costs quickly.

Ask 'Cost of what?' to fix the cost object.
Ask 'What happens if activity doubles?' Total doubles means variable; unchanged means fixed; partly rises means semi-variable.
Ask 'Is it future and different between options?' If yes, relevant; if it is already spent, it is sunk.
For unit versus centre, ask 'Am I measuring or collecting?' Measuring means cost unit; collecting means cost centre.

Common mistakes in Cost Concepts and Classification of Costs

Treating cost unit and cost centre as the same thing.
Both are used to accumulate or express cost, so they sound alike.
Fix: A cost unit is the measure (per tonne, per bed-day). A cost centre is the place or person where costs are collected (a department).
Saying fixed cost per unit is constant.
Students remember 'fixed' and apply it to the per-unit figure.
Fix: Total fixed cost is constant within the relevant range. Per-unit fixed cost falls as output rises. Variable cost is the reverse.
Classifying a cost in only one way and losing marks when the question asks for another basis.
Students memorise one example per category.
Fix: Remember that one cost has several tags. Factory rent is indirect, fixed, production cost and often uncontrollable for a shop-floor supervisor.
Including sunk cost in a decision.
Past spending feels important.
Fix: Cross out any cost already incurred or unavoidably committed. Only future costs that differ between alternatives count.
Calling a cost controllable or uncontrollable without naming the manager.
Students treat the label as a property of the cost.
Fix: State the level of management and period. Depreciation is uncontrollable for a department head but controllable by top management when buying assets.
Treating a semi-variable cost as fully fixed or fully variable.
The question gives one total figure.
Fix: Look for two data points and apply the high-low method to split the fixed and variable parts.

Worked examples

Example 1

A factory's power cost was ₹58,000 at 4,000 machine hours and ₹70,000 at 6,000 machine hours. Classify the cost by behaviour, split it into fixed and variable parts, and estimate the cost at 5,000 machine hours.

Show the solution

Power cost changes with activity but not in direct proportion, so it is semi-variable.
Variable rate = (70,000 − 58,000) ÷ (6,000 − 4,000) = 12,000 ÷ 2,000 = ₹6 per machine hour.
Fixed element = 58,000 − (6 × 4,000) = 58,000 − 24,000 = ₹34,000.
Check at 6,000 hours: 34,000 + 6 × 6,000 = 34,000 + 36,000 = ₹70,000, which matches.
Cost at 5,000 hours = 34,000 + 6 × 5,000 = 34,000 + 30,000 = ₹64,000.

Answer: Semi-variable cost; fixed ₹34,000, variable ₹6 per machine hour; estimated cost at 5,000 hours is ₹64,000.

Example 2

Sharma Furniture Ltd makes wooden tables. Classify each cost by traceability (direct or indirect) and behaviour (fixed or variable): (a) teak wood used in tables, (b) wages of carpenters paid per table made, (c) factory rent, (d) lubricant oil for machines. Also state the cost unit and one possible cost centre.

Show the solution

(a) Teak wood can be traced to each table, so it is direct. Usage rises with output, so it is variable.
(b) Carpenter wages paid per table are traceable, so direct, and they rise with output, so variable.
(c) Factory rent cannot be traced to one table, so it is indirect. It does not change with output within the relevant range, so it is fixed.
(d) Lubricant oil is not traceable to a single table, so indirect. Its use rises broadly with machine use, so it is variable.
Cost unit: one table, because cost is expressed per table.
Cost centre: the carpentry or polishing department, where costs are collected.

Answer: (a) direct, variable; (b) direct, variable; (c) indirect, fixed; (d) indirect, variable. Cost unit: one table. Cost centre: for example, the carpentry department.

Exam tips

In Section A, expect short statements on definitions: cost unit versus cost centre, sunk versus opportunity cost, controllable versus uncontrollable. Read all four options before choosing, as two often look similar.
In written answers, give a one-line definition and one rupee-based example for each class. This earns marks beyond the bare label.
When data for a semi-variable cost is given at two activity levels, use the high-low method and show the check calculation.
For decision questions, list the costs you excluded and why. Step marks are often given for excluding sunk costs.
Practise tagging one cost under several bases; questions often ask for two or three classifications of the same list.

Practice questions from Introduction to Cost Accounting

Cost Concepts and Classification of Costs in other exams

The same ground in other exams, if you are preparing for more than one or want another angle on it.

Cost Concepts and Classification of Costs: frequently asked questions

What is the difference between a cost unit and a cost centre?

A cost unit is the unit in which cost is measured, such as per tonne or per passenger-km. A cost centre is a location, person or equipment where costs are collected, such as a machining department. One is a measure and the other is a collection point.

What is a cost object with examples?

A cost object is anything for which you want to know the cost. Examples include a product, a job, a department, a customer, a project or a delivery route. The cost object decides which costs count as direct.

Is a semi-variable cost fixed or variable?

It is both. It has a fixed element that does not change with activity and a variable element that does. A telephone bill with fixed rental plus a charge per call is a common example. You split it using the high-low method or other given data.

What is the difference between controllable and uncontrollable costs?

A controllable cost can be influenced by a particular manager within a given period. An uncontrollable cost cannot. The same cost may be controllable at a higher level of management, so always state whose control you mean.