2.3 Costing Methods: Job, Batch, Unit, and Service Costing

Costing Methods: Job, Batch, Unit, and Service Costing

Businesses utilize different costing systems depending on how products or services are manufactured and delivered. The AAT Q2022 MATS syllabus (topic 2.5) requires candidates to record cost information using four costing systems — Job Costing, Batch Costing, Unit Costing, and Service Costing — to understand the appropriate choice of system for different business sectors, and to appreciate the effect of waste on costing inputs and outputs.

Syllabus note: Detailed process costing (process accounts with normal and abnormal losses) and LIFO inventory valuation belonged to the previous AQ2016 syllabus and were removed under Q2022 — they are not assessed in MATS. Continuous, high-volume production is costed in Q2022 MATS using unit costing with cost-per-equivalent-unit calculations, covered below.

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1. Job Costing

Job costing is applied when work is undertaken to a customer's specific, bespoke requirements. Each job is unique, short in duration, and separately identifiable.

• Typical Applications: Custom furniture manufacturing, commercial printing, building repair work, advertising campaigns, bespoke auditing engagements, and specialist vehicle conversion.

The Job Cost Card

A Job Cost Card (or job account) is opened for every specific order to collect and track incurred expenditure:

1. Direct Materials: Identified from material requisition notes specifically coded to the job number.
2. Direct Labour: Identified from employee job time tickets or electronic time-card entries.
3. Direct Expenses: Specific costs incurred solely for that job (e.g., hire of specialist equipment, architectural fees, or design licenses).
4. Prime Cost: The sum of all direct costs ($ \text{Prime Cost} = \text{Direct Materials} + \text{Direct Labour} + \text{Direct Expenses} $).
5. Absorbed Production Overheads: Applied using a pre-determined Overhead Absorption Rate (OAR) based on direct labour hours, machine hours, or direct labour cost.
6. Total Production Cost: Prime Cost + Absorbed Production Overheads.
7. Non-Production Overheads & Profit Margin: Selling, distribution, and administration overheads are added, followed by the target profit mark-up (percentage added to cost) or profit margin (percentage of selling price) to establish the final customer quote or invoice price.

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2. Batch Costing

Batch costing is a variation of job costing applied when a group of identical items are manufactured together in a discrete production run (a batch).

• Typical Applications: Bakeries producing 500 loaves of artisan bread, pharmaceutical firms manufacturing 20,000 antibiotic tablets, clothing factories producing 300 pairs of trousers, and component manufacturing.

Calculating Cost per Unit in a Batch

Costs are collected for the batch as a whole on a batch cost card in the same manner as a job. A key element unique to batch costing is Batch Setup Costs (the cost of cleaning, retooling, and calibrating machinery prior to running the batch).

To calculate the cost per individual finished unit within a batch:

$\text{Cost per Unit in Batch} = \frac{\text{Total Batch Direct Costs} + \text{Batch Setup Costs} + \text{Absorbed Overheads}}{\text{Number of Good Units Produced in Batch}}$

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3. Unit Costing

Unit costing (sometimes called single or output costing) is applied when identical units are produced continuously or in very large volumes, so that no individual job or batch can be separately identified.

• Typical Applications: Cement manufacture, industrial chemicals, brewing and soft-drink bottling, paper production, quarrying, and utility generation.

Cost per Unit of Good Output

Because every unit is identical, the unit cost is found by dividing the total production cost of the period by the number of good units produced:

$\text{Cost per Unit} = \frac{\text{Total Production Cost of Period}}{\text{Units of Good Output Produced}}$

The Effect of Waste on Costing Inputs and Outputs

Continuous production often involves expected (normal) waste — shrinkage, evaporation, or off-cuts inherent in efficient operations. Waste reduces the good output over which period costs are spread, so it raises the cost per good unit:

• Expected waste is assigned no production cost; its cost is borne by the good output.
• If the expected waste can be sold as scrap, the scrap proceeds are deducted from total input costs before calculating the unit cost.
• Waste in excess of the expected level is an inefficiency cost: it is valued at the full cost per good unit and written off as a period expense, never absorbed into the cost of good output.

Cost per Equivalent Unit (Work-in-Progress)

At a period end, some units may be only partly complete. To state partially finished work-in-progress (WIP) in terms of finished production, MATS candidates calculate equivalent units:

$\text{Equivalent Units} = \text{Physical Units in WIP} \times \text{Percentage Completion}$

$\text{Cost per Equivalent Unit} = \frac{\text{Total Costs to Allocate}}{\text{Completed Units} + \text{Equivalent Units in Closing WIP}}$

Example: 1,000 units in closing WIP that are 60% complete equal 600 equivalent units of finished production.

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4. Service Costing

Service costing is used by organizations that deliver intangible services rather than manufacturing tangible goods.

• Typical Applications: Hospitals, hotels, road haulage and courier firms, airlines and rail operators, colleges, accountancy and law practices, and IT support providers.

Composite Cost Units

Services cannot be held in inventory, and most of their costs are overheads rather than direct materials. Costs are therefore measured using a composite cost unit that combines two dimensions of service output:

$\text{Cost per Service Unit} = \frac{\text{Total Service Costs for the Period}}{\text{Number of Service Units Supplied}}$

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Worked Numerical Examples

Worked Example 1: Comprehensive Job Cost Card & Pricing

Scenario: Apex Design Ltd receives Job #J-805 for a custom timber display unit. The job records show:

• Direct Materials: £2,400
• Direct Labour: 80 hours @ £18 per hour = £1,440
• Direct Expenses (specialist router hire): £360
• Production Overhead Absorption Rate: £25 per direct labour hour
• Administration & Selling Overheads: 15% of total production cost
• Target Profit Margin: 20% on selling price

Step-by-Step Job Costing Calculation:

1. Calculate Prime Cost: $\text{Prime Cost} = £2,400 + £1,440 + £360 = £4,200$

2. Calculate Absorbed Production Overheads: $\text{Absorbed Overheads} = 80\text{ labour hours} \times £25 = £2,000$

3. Calculate Total Production Cost: $\text{Total Production Cost} = £4,200 + £2,000 = £6,200$

4. Add Administration & Selling Overheads: $\text{Admin/Selling Overheads} = 15\% \times £6,200 = £930$ $\text{Total Cost of Job} = £6,200 + £930 = £7,130$

5. Calculate Selling Price using 20% Profit Margin: $\text{Selling Price} = \frac{\text{Total Cost}}{1 - \text{Profit Margin}} = \frac{£7,130}{1 - 0.20} = \frac{£7,130}{0.80} = £8,912.50$ $\text{Profit Amount} = £8,912.50 - £7,130 = £1,782.50$

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Worked Example 2: Unit Costing with Waste

Scenario: SynthChem Ltd produces a single identical industrial chemical in continuous output. During March, the following data was recorded:

• Input Materials: 5,000 kg @ £5.00/kg = £25,000
• Conversion Costs (Direct Labour & Overheads): £19,000
• Total Input Cost: £44,000
• Expected waste: 20% of input volume (1,000 kg), which can be sold for scrap value of £4.00 per kg.
• Actual good output transferred to finished goods: 3,800 kg. Actual total waste: 1,200 kg (comprising 1,000 kg expected waste and 200 kg unexpected excess waste).

Step-by-Step Unit Costing Calculation:

1. Calculate Expected Waste & Scrap Credit: $\text{Expected Waste} = 20\% \times 5,000\text{ kg} = 1,000\text{ kg}$ $\text{Scrap Value Credit} = 1,000\text{ kg} \times \pounds 4.00 = \pounds 4,000$
2. Calculate Net Cost of Production & Expected Good Output: $\text{Net Production Cost} = \text{Total Inputs} - \text{Scrap Credit} = \pounds 44,000 - \pounds 4,000 = \pounds 40,000$ $\text{Expected Good Output} = 5,000\text{ kg} - 1,000\text{ kg} = 4,000\text{ kg}$
3. Calculate Cost per kg of Good Output: $\text{Cost per kg} = \frac{\text{Net Production Cost}}{\text{Expected Good Output}} = \frac{\pounds 40,000}{4,000\text{ kg}} = \pounds 10.00\text{ per kg}$
4. Value the Outputs:
   • Finished Goods (3,800 kg): $3,800\text{ kg} \times \pounds 10.00 = \mathbf{\pounds 38,000}$
   • Unexpected Excess Waste (200 kg): $200\text{ kg} \times \pounds 10.00 = \mathbf{\pounds 2,000}$ (written off as a period expense — an inefficiency cost, NOT absorbed into good output)
   • Expected Waste Scrap (1,000 kg): $1,000\text{ kg} \times \pounds 4.00 = \mathbf{\pounds 4,000}$ (scrap revenue already credited against input costs)

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Worked Example 3: Cost per Equivalent Unit (Closing WIP)

Scenario: At the end of April, SynthChem Ltd has £46,000 of production costs to allocate. Completed production is 4,000 units, and closing work-in-progress is 1,000 units that are 60% complete.

1. Equivalent Units in Closing WIP: $1,000\text{ units} \times 60\% = \mathbf{600\text{ equivalent units}}$
2. Cost per Equivalent Unit: $\frac{\pounds 46,000}{4,000 + 600} = \frac{\pounds 46,000}{4,600} = \mathbf{\pounds 10.00}$
3. Cost Allocation:
   • Completed output: $4,000 \times \pounds 10.00 = \mathbf{\pounds 40,000}$
   • Closing WIP: $600 \times \pounds 10.00 = \mathbf{\pounds 6,000}$

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Worked Example 4: Service Costing with a Composite Cost Unit

Scenario: Apex Haulage Ltd operates a small freight fleet. Total operating costs for the quarter are £540,000, and the fleet carries loads totaling 900,000 tonne-miles.

$\text{Cost per Tonne-Mile} = \frac{\pounds 540,000}{900,000\text{ tonne-miles}} = \mathbf{\pounds 0.60\text{ per tonne-mile}}$

Management uses this composite unit cost to quote freight rates and to monitor fleet efficiency between periods.

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Choosing the Appropriate Costing System (AAT topic 2.5.1)

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Common AAT Exam Traps

• Exam Trap 1: Confusing Profit Mark-up with Profit Margin: Mark-up is % added to Cost (Price = Cost x (1 + %)); Margin is % of Selling Price (Price = Cost / (1 - %)).
• Exam Trap 2: Selecting the Wrong Costing System for the Sector: Match the system to the output pattern — bespoke orders need job costing, discrete groups need batch costing, continuous identical output needs unit costing, and intangible services need service costing with a composite cost unit.
• Exam Trap 3: Forgetting the Scrap Credit for Expected Waste: Always deduct scrap proceeds from total input costs before deriving the cost per good unit; waste beyond the expected level is a period expense, never part of the good-unit cost.