MODULE III: PROCESS COSTING AND SERVICE COSTING

1. Process Costing: Concepts, Characteristics, and Operational Architecture

Process Costing (also known as Continuous Costing or Average Costing) is that method of cost accounting applied in mass-production manufacturing environments where raw materials pass through a succession of continuous, distinct, and standardized operational stages (termed "processes") to emerge as finished products. The finished output of the first process becomes the raw material input for the immediately succeeding process, continuing sequentially until the final process yields the marketable finished good.

Unlike job or contract costing, individual units of output in process industries are completely homogeneous, standardized, and physically indistinguishable from one another. Consequently, costs cannot be traced to individual units during production. Instead, costs of materials, labor, and overheads are accumulated for each process over a designated accounting period, and the average cost per unit is ascertained by dividing the total process cost by the net volume of sound units produced:

2. Treatment of Process Losses, Wastage, and Abnormal Gains

In manufacturing operations involving chemical reactions, heating, crushing, distillation, evaporation, or mechanical shaping, raw material inputs inevitably suffer physical shrinkage, shrinkage in volume, evaporation, chemical decomposition, or spoilage. Cost accounting classifies these losses into two distinct categories: Normal Loss and Abnormal Loss, alongside the counter-phenomenon of Abnormal Gain.

3. Joint Products and By-Products: Principles and Cost Apportionment

In many continuous process industries, the processing of a common raw material simultaneously yields two or more distinct products. Depending on their relative economic importance, these products are classified as Joint Products or By-Products:

• Joint Products: Two or more products of substantial, comparable economic and commercial value produced simultaneously from a single raw material input through a common manufacturing process (e.g., in petroleum refining: petrol, diesel, kerosene, aviation fuel; in dairy: butter, cheese, cream). Neither product can be termed primary; each represents a substantial commercial revenue stream.
• By-Products: Products of secondary, minor, or incidental commercial value that emerge inevitably in the course of manufacturing the main product (e.g., molasses and bagasse in sugar manufacturing; coal tar and ammonia in coke manufacturing; hides and tallow in meatpacking).
• Split-Off (Separation) Point: The exact stage in the manufacturing flow where the joint products or by-products become physically distinct and identifiable from each other. Prior to this point, all costs incurred are termed Joint Costs (Pre-separation Costs). After this point, costs incurred are termed Subsequent (Post-separation) Processing Costs.

4. Equivalent Production in Work-in-Progress Inventories

In continuous processing, a department rarely empties out its entire production floor at the stroke of the midnight balance sheet date. There almost always remains a volume of partially processed units in the machinery—termed Work-in-Progress (WIP).

Because partially completed units have absorbed some raw materials, labor, and overheads, but not the full quota of a completed product, physical units cannot simply be added together to compute unit costs. They must be mathematically converted into an equivalent number of fully completed units, termed Equivalent Units of Production:

5. Service Costing (Operating Costing): Structure and Transport Logistics

Service Costing (traditionally designated as Operating Costing) is that method of costing applied in undertakings that do not manufacture tangible goods, but instead render unique, measurable, non-storable economic services. Typical service sectors include passenger transport, freight logistics, hospitals, electricity generation, hotels, and educational institutions.

Composite Cost Units in Service Undertakings

Unlike manufacturing where a single physical count (units, tonnes, litres) suffices, the cost of rendering a service is driven by two interdependent variables: volume/capacity and distance/time. Consequently, service costing employs Composite (Dual) Cost Units:

• Passenger Transport: Passenger-Kilometre ($\text{Number of Passengers Carried}\times \text{Distance Traveled in Km}$).
• Goods / Freight Haulage: Tonne-Kilometre ($\text{Weight of Freight Carried in Tonnes}\times \text{Distance Traveled in Km}$).
  • Absolute Tonne-Kilometres: Sum of the products of each trip's weight multiplied by distance:
  $$\text{Absolute Tonne-Km}=\sum ({\text{Weight}}_i\times {\text{Distance}}_i)$$
  • Commercial Tonne-Kilometres: Total round-trip distance multiplied by the simple average weight carried:
  $$ext{Commercial Tonne-Km} = ext{Total Journey Km} imes left( rac{ ext{Total Weight Carried Across All Legs}}{ ext{Number of Legs}} ight)$$
• Hospitals: Patient-Day (Number of in-patients × days hospitalized).
• Hotels: Occupied Room-Day (Number of rooms occupied × days stayed).
• Electricity Power Plants: Kilowatt-Hour (kWh).

Structural Architecture of a Transport Operating Cost Sheet

6. Comprehensive Numerical Illustrations

Illustration 1: Multi-Process Costing with Normal Loss, Abnormal Loss, and Abnormal Gain

Problem Statement: A product passes through two distinct processes, Process I and Process II, and then to Finished Stock. During the month of March 2026, the following data is provided:

Required: Prepare: (1) Process I Account; (2) Process II Account; (3) Abnormal Loss Account; (4) Abnormal Gain Account; and (5) Normal Loss Account.

Illustration 2: Transport Operating Costing & Freight Fare Computation

Problem Statement: Garuda Transport Company operates a fleet of 5 commercial trucks between City X and City Y, separated by a one-way distance of 100 kilometres. The operational data for the month of April 2026 is as follows:
• Each truck makes one round trip per day (100 km onward + 100 km return = 200 km daily).
• Capacity of each truck: 10 tonnes.
• Average load factor: Onward journey is operated at 100% capacity (10 tonnes); Return journey is operated at 60% capacity (6 tonnes).
• Each truck operates for 25 days during the month. All 5 trucks operated without downtime.
Monthly Expenditures for the fleet of 5 trucks:
• Drivers’ and cleaners’ wages: ₹1,50,000;
• Diesel, oil and lubricants: ₹2,40,000;
• Repairs and servicing: ₹60,000;
• Garage rent, insurance and road taxes: ₹90,000;
• Depreciation on trucks: ₹1,20,000;
• General management and office supervision: ₹60,000.
Required:
(a) Compute total Absolute Tonne-Kilometres and Commercial Tonne-Kilometres for the month;
(b) Prepare an Operating Cost Sheet showing cost per commercial tonne-kilometre;
(c) Calculate the freight rate to be charged per tonne-km if the company desires a profit margin of 20% on total revenue (freight).

7. Comprehensive Review & Self-Assessment Exercises