Unit 10: Marginal Costing and Profit Planning

Marginal costing is a technique of cost analysis and presentation, not a method of ascertaining cost like job or process costing. It separates cost by behaviour rather than by function, so that the effect of changes in activity on profit becomes visible. It underpins short-run decision-making and profit planning, and every tool in this unit rests on the cost classifications set out below.

I. Foundations of Marginal Costing

Marginal costing treats only variable costs as product costs and writes off fixed costs against the period's contribution. The technique grew out of the recognition (early 20th century management accounting) that fixed costs do not vary with output and so distort per-unit decisions when apportioned.

• Marginal cost: the additional cost of producing one more unit; in practice equal to total variable cost per unit (direct material + direct labour + variable overhead).
• Cost behaviour classification: every cost is split into two types.
  • Fixed cost: unchanged in total within the relevant range (e.g. rent of ₹1,20,000 p.a.), but falls per unit as output rises.
  • Variable cost: changes in total in proportion to output (e.g. ₹40 material per unit), but constant per unit.
  • Semi-variable cost: contains both elements and must be segregated (high-low method or least squares) before use.
• Contribution: the surplus of sales over variable cost, the pool from which fixed cost is met and profit earned.
• Key assumptions: selling price per unit is constant; cost can be neatly split into fixed and variable; fixed cost stays constant in total; production equals sales (no stock effect); and efficiency and product mix are unchanged.

Contribution (C) = Sales (S) - Variable Cost (V)
Profit (P) = Contribution - Fixed Cost (F)

• Symbols: S = total sales value, V = total variable cost, F = total fixed cost, C = contribution, P = profit.

II. Marginal Costing: Meaning and Objectives

Marginal costing is the ascertainment of marginal cost and the effect on profit of changes in volume or type of output by treating fixed and variable costs separately.

A. Meaning and Concept

The technique charges only variable cost to products and treats fixed cost as a period cost.

• Definition (CIMA sense): the ascertainment of marginal costs and of the effect of changes in volume or type of output by differentiating between fixed and variable costs.
• Stock valuation: closing stock and WIP are valued at variable cost only; fixed overhead is never carried forward in inventory.
• Contrast with absorption costing: number the two.
  1. Marginal costing: fixed cost fully written off in the period incurred; profit moves with sales.
  2. Absorption costing: fixed cost absorbed into units via an overhead rate; profit is influenced by stock movement, so building stock inflates reported profit.
• Profit reconciliation: the two methods differ in profit only by the fixed overhead contained in the change in stock: Difference = Fixed OH rate x change in units of stock.

B. Objectives of Marginal Costing

The purpose is to give management a decision-ready view of how profit responds to activity.

• Profit planning: shows how profit changes with volume, price or cost, feeding CVP and budgeting.
• Cost control: by isolating variable cost, it highlights controllable costs at operating level and fixes fixed cost as a policy decision.
• Decision support: provides the basis for pricing, make-or-buy, accept/reject of special orders, and dropping a product line.
• Simplified valuation: avoids arbitrary apportionment of fixed overhead to products, removing distortion in per-unit cost.
• Performance appraisal: contribution per unit of a limiting factor ranks products objectively.

C. Advantages and Limitations

Its usefulness is real but bounded by its assumptions.

• Advantages: simple to operate; avoids fixed-cost apportionment errors; prevents stock-driven profit manipulation; directly aids short-term decisions.
• Limitations: splitting semi-variable costs is imprecise; ignores that fixed costs are also part of true cost, so unsuitable for long-run pricing; understates stock for external reporting (not accepted under Ind AS 2 / AS 2, which require absorption); assumes linearity that fails at extreme volumes.

III. Cost-Volume-Profit (CVP) Analysis

CVP analysis studies how costs and profits react to changes in the volume of activity, so that management can plan the profit target and the sales needed to reach it.

A. Principle and Key Ratios

The core idea is that once variable cost per unit and fixed cost are known, profit is a straight function of volume.

• Purpose: answers "what sales give a target profit?" and "what happens to profit if price, cost or volume shifts?".
• P/V ratio (contribution to sales): measures the rate at which each rupee of sales generates contribution.

P/V Ratio = (Contribution / Sales) x 100
          = (Change in Profit / Change in Sales) x 100

• Contribution per unit: c = selling price per unit (s) - variable cost per unit (v).
• Improving the P/V ratio: raise selling price, cut variable cost per unit, or shift the mix toward high-contribution products.

B. Elements and Assumptions of CVP

CVP rests on the same behaviour split as marginal costing plus a linearity assumption.

• The three variables: cost, volume (activity level) and profit, with selling price treated as constant.
• Assumptions: cost splits cleanly into fixed and variable; both cost and revenue lines are linear over the relevant range; fixed cost is constant; product mix is stable; production equals sales.
• Relevant range: conclusions hold only within the activity band where fixed cost and the per-unit rates stay valid.

C. Applications in Profit Planning

CVP converts a profit goal into an operating plan.

• Target-profit sales: the volume needed to earn a desired profit.

Required Sales (value) = (Fixed Cost + Desired Profit) / P/V Ratio
Required Sales (units) = (Fixed Cost + Desired Profit) / Contribution per unit

• Worked example: s = ₹100, v = ₹60, so c = ₹40 and P/V = 40%. With F = ₹2,00,000 and desired profit ₹80,000: required units = (2,00,000 + 80,000)/40 = 7,000 units; required sales value = 2,80,000/0.40 = ₹7,00,000.
• Sensitivity checks: re-running the formula with a changed price or cost shows the profit impact before any decision is taken.

IV. Break-Even Point and Break-Even Analysis

Break-even analysis is the branch of CVP that finds the activity level at which total contribution exactly equals fixed cost, so profit is zero, and then studies profit and loss on either side of that level.

A. Break-Even Point Defined

The break-even point (BEP) is the sales volume where the firm neither profits nor loses.

• Condition: at BEP, Total Contribution = Fixed Cost, hence Sales = Fixed Cost + Variable Cost and profit is nil.
• In units:

BEP (units) = Fixed Cost / Contribution per unit
            = F / (s - v)

• In value:

BEP (value) = Fixed Cost / P/V Ratio

• Worked example (same data): BEP units = 2,00,000 / 40 = 5,000 units; BEP value = 2,00,000 / 0.40 = ₹5,00,000. Every unit beyond 5,000 adds ₹40 of profit.

B. Break-Even Analysis and the Break-Even Chart

Break-even analysis plots cost and revenue against volume to locate BEP and read off profit or loss at any level.

• Break-even chart: the x-axis shows output/sales volume, the y-axis shows cost and revenue in rupees.
  • Fixed cost line: horizontal, e.g. at ₹2,00,000.
  • Total cost line: starts at the fixed-cost intercept and rises by variable cost per unit.
  • Sales line: starts at the origin and rises by selling price per unit.
  • Break-even point: where the sales line cuts the total cost line; the wedge to its right is the profit area, to its left the loss area.
• Angle of incidence: the angle at which the sales line crosses the total cost line; a wide angle signals a high rate of profit once BEP is passed.
• Margin of safety (MOS): the excess of actual sales over break-even sales, a cushion against a fall in demand.

Margin of Safety = Actual Sales - Break-Even Sales
MOS Ratio (%) = (Margin of Safety / Actual Sales) x 100
MOS (value)   = Profit / P/V Ratio

• MOS example: at actual sales of ₹7,00,000, MOS = 7,00,000 - 5,00,000 = ₹2,00,000, i.e. 28.6% of sales; the firm can lose over a quarter of its sales before making a loss.

C. Uses and Limitations of Break-Even Analysis

The tool guides planning but must be read within its assumptions.

• Uses: sets minimum sales targets; tests the profit effect of price or cost changes; compares plant or product options; frames decisions on capacity and shutdown.
• Limitations: assumes strict linearity of cost and revenue; treats selling price and fixed cost as constant, which rarely holds across wide ranges; assumes a single product or a stable mix; ignores that production and sales may differ. Beyond the relevant range the straight lines break down and the BEP loses reliability.