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Cost and Management Accounting · Overheads - Absorption Costing Method

Capacity Levels, Idle Capacity and Special Overhead Treatments

Updated 4 October 2026 · Fact-checked

Capacity levels (normal, practical, actual) decide the base for absorbing fixed overheads. Idle capacity cost is fixed overhead of unused capacity: normal idle cost goes to production cost, abnormal idle cost goes to the Costing P&L. Administration, selling and R&D overheads follow their own treatment rules.

Understand Capacity Levels, Idle Capacity and Special Overhead Treatments

Every factory has a limit to what it can produce. Capacity is that limit. Fixed overheads do not change with output, so the level of capacity you choose as the base changes the overhead rate per unit.

There are four capacity levels. Full (theoretical) capacity is the output possible with no stoppages at all. Practical capacity is full capacity less unavoidable losses such as holidays, maintenance and setup time. Normal capacity is the average output expected over a few years, allowing for seasonal and cyclical swings. Actual capacity is what you really produced in the period.

Idle capacity is the part of available capacity that is not used. Its cost is the fixed overhead linked to it. Idle capacity cost = fixed overhead rate on the chosen base × idle units. If the idle capacity is due to normal causes (seasonal demand, unavoidable setup), it is normal idle capacity cost. It is absorbed into the cost of production by a higher rate. If it is due to abnormal causes (strike, machine breakdown, power failure, lack of orders through poor planning), it is abnormal idle capacity cost. It is not charged to products. It is written off to the Costing Profit and Loss Account.

Other overheads are treated by function. Administration overheads are generally not part of production cost. They are either charged as a separate element of total cost, or absorbed on a suitable base such as works cost or output. Any part clearly linked to the factory is treated as a factory overhead. Selling and distribution overheads are absorbed on a base such as sales value, units sold or cost of sales. Distribution costs after production, such as transport of finished goods, are not in product cost. Research and development cost for process improvement is treated as production overhead. Cost of a specific project may be charged to that project. Unsuccessful or general research is normally written off to the Costing P&L.

Key rules to remember

Fixed overhead rate per unit
Budgeted fixed overhead ÷ Capacity chosen (normal or practical)
A higher base gives a lower rate. Use the base the question names.
Idle capacity (units)
Capacity base − Actual output
Use the same base as the rate.
Idle capacity cost
Idle units × Fixed overhead rate per unit
Equals fixed overhead not absorbed by production.
Capacity utilisation %
Actual output ÷ Capacity base × 100
Check which base is asked for.
Treatment of idle capacity
Normal idle → production cost. Abnormal idle → Costing P&L
Decide by the cause of the idleness.
Treatment of special overheads
Administration: separate or on works cost. Selling and distribution: on sales or sales units. R&D: process-related to production overhead, unsuccessful to Costing P&L
State the base you use and why.

How to solve Capacity Levels, Idle Capacity and Special Overhead Treatments questions

Use this order for any question on capacity, idle cost or overhead treatment.

  1. 1Read which capacity base is given: normal, practical or full. Note actual output.
  2. 2Compute the fixed overhead rate = budgeted fixed overhead ÷ that base.
  3. 3Find idle units = base − actual output. Compute idle cost = idle units × rate.
  4. 4Read the cause of idleness. Split it into normal and abnormal parts.
  5. 5Absorb normal idle cost into the cost of production by spreading the unabsorbed fixed overhead over actual output, which gives a higher rate per unit. Send abnormal idle cost to the Costing P&L.
  6. 6Classify each remaining overhead as factory, administration, selling, distribution or R&D, and apply its treatment.
  7. 7Build the cost sheet or statement in proper order. State your assumptions in one line.

Quickest way: Rate, idle units, cause, place

When to use it: Use when the question gives capacity figures and asks for cost per unit or the idle cost treatment, and for MCQs.

  1. Write rate = fixed overhead ÷ base. Do this first and box it.
  2. Multiply by idle units to get idle cost. Cross-check: rate × actual output + idle cost = total fixed overhead.
  3. Ask one question: normal or abnormal cause? Normal goes into cost, abnormal to Costing P&L.
  4. In MCQs, eliminate options that load abnormal idle cost into product cost.
  5. In written answers, show the rate, the idle units and the destination of each amount on separate lines. Each line earns step marks.

Common mistakes in Capacity Levels, Idle Capacity and Special Overhead Treatments

  • Using actual output instead of the stated capacity base to compute the overhead rate.

    Students are used to dividing by units produced.

    Fix: Divide by normal or practical capacity when the question says so. Use actual output only when no base is given.

  • Loading abnormal idle capacity cost into product cost.

    Students treat all unabsorbed fixed cost as production cost.

    Fix: Check the cause. Strikes, breakdowns and power failure are abnormal and go to the Costing P&L.

  • Confusing normal capacity with practical capacity.

    Both are below full capacity.

    Fix: Practical capacity is full capacity less unavoidable losses. Normal capacity is average expected output over several periods, including demand effects.

  • Including administration overheads in production cost by default.

    All overheads are lumped together.

    Fix: Treat them as a separate element unless they clearly relate to the factory.

  • Including finished goods transport in the cost of production.

    Students see 'transport' and think of the factory.

    Fix: Carriage on finished goods is distribution cost. Carriage inward on materials is part of material cost.

  • Writing off all R&D to the Costing P&L.

    Students remember only one rule.

    Fix: Process improvement research goes to production overhead. Project-specific research goes to that project. Unsuccessful research is written off.

Worked examples

Example 1

A factory has practical capacity of 20,000 units per month. Normal capacity is 16,000 units. Budgeted fixed overhead is ₹4,80,000 per month. Actual output is 14,000 units. Of the shortfall from normal capacity, 1,000 units were lost due to a machine breakdown. Find the fixed overhead rate on normal capacity, the total idle capacity cost, and the amounts treated as normal and abnormal.

Show the solution
  1. Fixed overhead rate on normal capacity = ₹4,80,000 ÷ 16,000 = ₹30 per unit.
  2. Idle units against normal capacity = 16,000 − 14,000 = 2,000 units.
  3. Idle capacity cost = 2,000 × ₹30 = ₹60,000.
  4. Abnormal idle units = 1,000 (breakdown). Abnormal cost = 1,000 × ₹30 = ₹30,000.
  5. Remaining 1,000 units are due to normal causes. Normal idle cost = 1,000 × ₹30 = ₹30,000.
  6. Check: fixed overhead absorbed = 14,000 × ₹30 = ₹4,20,000. Unabsorbed = ₹4,80,000 − ₹4,20,000 = ₹60,000. This matches.

Answer: Rate is ₹30 per unit. Idle capacity cost is ₹60,000, of which ₹30,000 is abnormal and written off to the Costing P&L. The other ₹30,000 is normal and is treated as part of production overhead.

Example 2

For a month, a firm reports: works cost of ₹6,00,000 for 10,000 units produced and sold, administration overheads ₹90,000, selling overheads ₹40,000, distribution overheads ₹20,000. Research on improving the production process cost ₹30,000 and is to be treated as a production overhead. A strike caused idle time cost of ₹15,000. This is not included in the figures above. Prepare the cost per unit and state the treatment of each item.

Show the solution
  1. Process research of ₹30,000 goes to production overhead. Works cost becomes ₹6,00,000 + ₹30,000 = ₹6,30,000.
  2. The strike is abnormal. The ₹15,000 is excluded from cost and written off to the Costing P&L.
  3. Cost of production = ₹6,30,000. Per unit = ₹6,30,000 ÷ 10,000 = ₹63.
  4. Add administration overheads ₹90,000. Cost of goods sold = ₹6,30,000 + ₹90,000 = ₹7,20,000.
  5. Add selling ₹40,000 and distribution ₹20,000. Cost of sales = ₹7,20,000 + ₹60,000 = ₹7,80,000.
  6. Cost of sales per unit = ₹7,80,000 ÷ 10,000 = ₹78.

Answer: Cost of production is ₹63 per unit and cost of sales is ₹78 per unit. The strike cost of ₹15,000 is written off to the Costing P&L and excluded from product cost.

Exam tips

  • Always underline the capacity base in the question. A rate on the wrong base loses every later mark.
  • Show the check: rate × actual output + idle cost = total fixed overhead. It catches errors fast.
  • In theory answers, give the cause-based rule for idle capacity and one example for each type.
  • In a cost sheet, place administration after works cost and selling and distribution after that. Do not mix them into factory overhead.
  • MCQs often test a single rule, such as where abnormal idle cost goes. Learn the destinations by heart.

Practice questions from Overheads - Absorption Costing Method

Capacity Levels, Idle Capacity and Special Overhead Treatments: frequently asked questions

What is the treatment of idle capacity cost in CA Intermediate?

Normal idle capacity cost is absorbed into production cost. Abnormal idle capacity cost is not charged to products and is written off to the Costing Profit and Loss Account. The cause of the idleness decides which applies.

What is the difference between normal capacity and practical capacity?

Practical capacity is full capacity less unavoidable losses like maintenance and holidays. Normal capacity is the average output expected over a period long enough to cover seasonal and cyclical changes. Normal capacity is generally at or below practical capacity.

How are administration overheads treated in cost accounting?

They are generally treated as a separate element of cost, not included in production cost. They can be absorbed on a base such as works cost or output. Any part that clearly relates to the factory is treated as factory overhead.

How are selling and distribution overheads absorbed?

They are absorbed on a base such as sales value, units sold or cost of sales. The choice should reflect what causes the cost. Costs after production, like carriage on finished goods, are not part of product cost.