Study PM by learning which assumptions each technique requires, not just how to compute it. For administrative details such as booking and current exam formats, use the ACCA official website; this guide focuses on the concepts the syllabus tests.
Limiting factor or throughput accounting: choosing the right engine for a scarce-resource question
Use limiting factor analysis when material or labour is scarce and costs behave conventionally; use throughput accounting when a bottleneck process is named and material is the dominant variable cost.
The two approaches differ in what they treat as variable. Limiting factor analysis assumes contribution behaves normally, so both variable production costs and other variable costs flex with output. Throughput accounting, built on the theory of constraints, treats only material as truly variable in the short run and treats labour and most overheads as fixed, so ranking uses throughput per unit of bottleneck time rather than contribution per unit.
Worked scenario: a factory makes two products. Product A sells at 40 with material cost 15 and needs 2 bottleneck minutes; Product B sells at 55 with material cost 30 and needs 3 bottleneck minutes. A plausible mistake is ranking by sales price, which favours B first. The better decision ranks by throughput per bottleneck minute: A gives 25 over 2 minutes = 12.5 per minute, B gives 25 over 3 minutes = 8.33 per minute, so maximise A first. It matters because the optimal plan, and the profit figure in the final requirement, changes completely with the wrong ranking.
- Scarce material or labour stated directly, normal variable costs: limiting factor analysis with contribution per scarce unit.
- Bottleneck process, machine-paced plant, labour treated as fixed: throughput accounting with throughput per constraint hour.
- Fixed costs in throughput accounting are deducted as one block after total throughput, not allocated per unit.
Relevant costing for one-off orders: the avoidability test applied line by line
A cost is relevant only if it is a future, incremental cash flow that differs between options. Sunk costs, committed costs, apportioned overheads, and notional accounting figures are excluded; opportunity costs of scarce resources are included.
Apply a two-step test to every line item before it enters your quote or decision. First, is it a future cash flow? Depreciation, apportioned head office charges, and the original purchase price of materials already held all fail. Second, is it incremental to this decision? Costs that will be incurred anyway, such as salaried staff who remain employed, are not relevant even though they are cash and future.
Worked scenario: a one-off order needs 500 units of material already in stores, bought at 8 per unit, now resellable at 5, or usable in another job that would otherwise buy a substitute at 6 per unit. A plausible mistake is valuing the material at the 8 original cost, inflating the quote and losing the order. The better decision uses 6 per unit, the higher of the 5 resale value and the 6 alternative-use value, because using the material here sacrifices the more valuable of the two alternatives. It matters because a quote built on book cost can reject profitable work or accept unprofitable work.
Variance analysis after the calculation: splitting mix, yield, planning and operational effects
A favourable variance can still signal problems, and a total materials variance hides two separate stories. PM asks you to decompose variances into mix and yield components, and into planning versus operational causes, then interpret them together.
Mix and yield variances answer different questions. The mix variance compares the actual input proportions with the standard proportions, valued at standard cost: did we use a dearer or cheaper blend than planned? The yield variance compares actual output with the output the actual total input should have produced: did the process convert efficiently? A favourable mix variance from substituting cheaper material can coexist with an adverse yield variance if the cheaper blend produced more rejects, so neither number is meaningful alone.
Worked scenario: standard input is 2 kg per unit in a 50/50 blend of materials X and Y, where Y is the cheaper material, at a standard 4 per kg. Actual input of 2,100 kg, blended 40% X and 60% Y, produces 1,000 units. A plausible mistake is reporting a single adverse usage variance and blaming the process. The better decision splits it: 2,100 kg at standard yield should have produced 1,050 units, so the yield variance is adverse by 50 units; the mix shifted 10 percentage points toward cheaper Y, producing a favourable mix effect. It matters because a supplier substitution shows up in mix, while process faults show up in yield, and the corrective actions differ.
ROI versus residual income in divisional appraisal: why a profitable division can reject a good project
Return on investment is a percentage that can make managers reject projects earning above the cost of capital but below the division's current return. Residual income is an absolute sum that accepts any project earning above the imputed interest rate.
ROI divides controllable profit by controllable investment, so any project that dilutes the division's percentage looks bad to the manager even when it creates value for the company. Residual income subtracts an imputed interest charge on the investment from profit, so a project is acceptable if it earns more than the imputed rate. The two can rank the same division differently, and a question may ask you to demonstrate exactly that divergence for one candidate project.
Worked scenario: a division has profit of 90 on investment of 600, an ROI of 15%. A proposed project adds profit of 26 on investment of 200, a 13% return, when the company's cost of capital is 10%. A plausible mistake is the manager declining the project because 13% drags the divisional ROI down to roughly 14.5%. The better decision uses residual income: current RI is 90 minus 10% of 600 = 30; after the project it is 116 minus 10% of 800 = 36, so the project raises RI by 6 and should be accepted. It matters because the percentage lens destroys company value that the absolute lens reveals.
Transfer pricing under spare and full capacity: one general rule with a capacity condition
The general rule sets a transfer price at marginal cost plus the opportunity cost to the supplying division. With spare capacity that opportunity cost is often zero, so marginal cost suffices; at full capacity it includes the lost external contribution.
Start every transfer pricing scenario by establishing the supplying division's capacity position. With idle capacity, an internal sale costs the supplier only the marginal cost of production, so a price at or above marginal cost can leave both divisions better off. At full capacity, each unit transferred sacrifices external contribution, so the minimum price rises to marginal cost plus that forgone contribution. Goal congruence, not any single number, is the evaluation criterion.
Worked scenario: Division M's product costs 20 variable per unit and sells externally at 35; Division N can buy the equivalent externally at 34. M is at full capacity. A plausible mistake is setting the transfer at marginal cost, 20, which would push M to sell nothing internally and strand N's order. The better decision recognises that each internal unit costs M the 15 external contribution, so the minimum transfer price is 35; N will then buy outside at 34, which is the correct company outcome because external purchase is cheaper for the group. It matters because a mechanical marginal-cost price would force a transfer destroying 1 per unit of group profit.
Budgeting choices and behaviour: matching incremental, zero-based, flexible and rolling budgets to the scenario
Incremental budgeting adjusts last period's figures; zero-based budgeting justifies every activity from scratch; flexible budgets flex for actual activity; rolling budgets extend continuously. Each suits different conditions and carries distinct behavioural consequences.
Match the technique to the cost behaviour in the scenario. Incremental budgeting is quick but entrenches last year's inefficiencies, suiting stable, largely discretionary overheads. Zero-based budgeting forces ranking of decision packages and suits discretionary support costs such as advertising or training, but its time demands make it impractical for every line every year. Flexible budgets are not a forecasting tool: they restate the fixed budget at actual activity so variance analysis compares like with like.
Practical exercise: take a small business's or your household's monthly spending and build two budgets for next month, one incremental (last month plus 5%) and one zero-based (justify each category from zero). Expected observations: the incremental version preserves one or two legacy costs you cannot justify, while the zero-based version takes far longer and forces you to rank discretionary items such as subscriptions. This mirrors why ZBB is reserved for high-value discretionary overheads rather than applied universally, and why imposed budgets invite slack while participative budgets invite padding.
A practice sequence and readiness rubric tied to scenario identification
Organise revision by decision type rather than by syllabus chapter: scarce resources, one-off decisions, variance investigation, divisional appraisal, transfer pricing, and budgeting systems. Drill each until you can name the governing assumption before calculating.
A realistic sequence over a revision block: first, rebuild the technique engine for each topic with short calculations until formulas are automatic. Second, practise scenario identification, reading a question and writing one sentence stating which technique applies and why, before any numbers. Third, move to full multi-requirement questions combining a calculation with written interpretation, because written marks reward the reasoning a technique's assumptions justify.
Use an error log as your self-check rubric. After each practice attempt, record the topic, the technique chosen, whether the assumption stated was correct, and whether your interpretation followed from your numbers. Review weekly: recurring assumption errors mean reread the concept; correct assumptions with arithmetic slips mean drill calculations; correct numbers with weak commentary means practise writing implications in terms of goal congruence and controllability. Treat a self-assessed score on these dimensions as a learning milestone, not a prediction of any official result.
- Readiness check 1: you can state the assumption that triggers each technique without notes.
- Readiness check 2: you can produce a full worked answer for one scenario per topic from memory.
- Readiness check 3: you can explain in two sentences why a technique's answer changes if a key condition, such as capacity or avoidability, changes.
- Drill: build flashcards showing a short scenario on the front and the correct technique plus its key assumption on the back; practise until selection is instantaneous.
| Scenario signal | Matching technique | Key assumption to state |
|---|---|---|
| Scarce material or labour, normal variable costs | Limiting factor analysis (contribution per scarce unit) | All variable costs flex with output |
| Bottleneck machine, material-led costs | Throughput accounting (throughput per constraint hour) | Only materials variable; labour and overheads fixed short-term |
| One-off contract, special order | Relevant costing | Only future, incremental cash flows count; scarce items carry opportunity cost |
| Actual output differs from budget | Flexible budgeting and variance analysis | Budget must be flexed before comparison is meaningful |
| Division offered a project near its current ROI | Residual income alongside ROI | Percentage measures can reject value-creating projects |
| Internal sale between divisions | Transfer pricing (marginal cost plus opportunity cost) | Minimum price depends on the supplying division's capacity position |
References and further reading
Use these references to explore the concepts and check the latest information from the relevant organizations.