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Imagine Rajesh & Co. Pvt. Ltd. gets a surprise order from a foreign buyer at a price lower than their usual selling price. Should they accept it? This is exactly what short-term decision making is about — and the golden rule is: ignore fixed costs, focus on contribution.

In short-term decisions, fixed costs are already committed — rent, salaries, depreciation — they don't change whether you accept that order or not. What does change is the contribution each unit brings in. Contribution = Selling Price − Variable Cost. As long as a decision gives you positive contribution, it adds to profit (or reduces loss). This is the core logic of marginal costing applied to decisions.

There are four classic short-term decisions the ICAI loves to test: (1) Accept or Reject a Special Order — accept if selling price > variable cost AND spare capacity exists. (2) Make or Buy — make if variable cost of making < purchase price (compare contributions, not total costs). (3) Product Mix with a Limiting Factor — when a resource like machine hours or raw material is scarce, rank products by contribution per unit of limiting factor (not just contribution per unit). (4) Shut Down or Continue — shut down only if the loss from continuing exceeds the avoidable fixed costs saved. These four scenarios cover 80% of exam questions in this chapter. This topic is asked every exam — typically as a 10-mark problem or a 5-mark decision scenario. The examiner always hides fixed costs to trick you into including them. Don't fall for it. Your mantra: short-term = contribution is king, fixed costs are passengers.

📊 Worked example

Example 1 — Special Order Decision

Rajesh & Co. manufactures fans. Normal data per unit: Selling Price ₹1,200, Variable Cost ₹750, Fixed Overhead ₹200, Total Cost ₹950, Profit ₹250. Current output: 8,000 units/month against a capacity of 10,000 units.

A foreign buyer offers ₹900 per unit for 1,500 units. Should Rajesh accept?

Working:

Spare capacity = 10,000 − 8,000 = 2,000 units → Order of 1,500 units fits within spare capacity ✓

Contribution from special order = Selling Price − Variable Cost = ₹900 − ₹750 = ₹150 per unit

Total additional contribution = 1,500 × ₹150 = ₹2,25,000

Fixed costs — NO change (capacity already available).

Decision: Accept the order. It adds ₹2,25,000 to profit.

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Example 2 — Limiting Factor / Product Mix

Ms. Iyer's firm makes two products, P and Q. Machine hours available: 4,000 hrs/month.

| | Product P | Product Q |

|---|---|---|

| Selling Price | ₹500 | ₹400 |

| Variable Cost | ₹300 | ₹200 |

| Contribution | ₹200 | ₹200 |

| Machine hrs/unit | 4 hrs | 2 hrs |

Max demand: P = 600 units, Q = 800 units.

Working:

Contribution per machine hour:

  • P = ₹200 ÷ 4 = ₹50/hr
  • Q = ₹200 ÷ 2 = ₹100/hr

Rank: Q first, then P.

Produce Q first: 800 units × 2 hrs = 1,600 hrs used → Remaining = 2,400 hrs

Produce P: 2,400 ÷ 4 = 600 units (meets full demand)

Total hrs used = 1,600 + 2,400 = 4,000 hrs ✓

Total Contribution = (800 × ₹200) + (600 × ₹200) = ₹1,60,000 + ₹1,20,000 = ₹2,80,000

⚠️ Common exam mistakes

  • Don't include fixed costs when evaluating a special order — fixed costs don't change with a one-off order if spare capacity exists. Only compare selling price vs. variable cost to find contribution.
  • Don't rank products by contribution per unit when a limiting factor exists — always rank by contribution per unit of the scarce resource (machine hours, kg of material, etc.). Equal contribution per unit doesn't mean equal priority.
  • Don't forget to check spare capacity for special orders — if the order exceeds spare capacity, you must sacrifice normal sales, and that lost contribution becomes an opportunity cost to factor in.
  • Don't compare total costs in Make-or-Buy decisions — fixed costs absorbed in 'make' cost are not avoidable. Compare variable cost of making vs. purchase price (and add any avoidable fixed costs if the facility is truly shut down).
  • Don't confuse 'shut down' savings with total fixed costs — only avoidable fixed costs are saved on shutdown. Committed fixed costs (like long-term lease) continue regardless. Only shut down if avoidable fixed costs > contribution lost.
📖 Reference: Decision Making — Institute of Chartered Accountants of India
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