ACCA PM common mistakes
ACCA PM · Understand the traps and how to avoid them.
When a question gives a limiting factor and asks for the optimal production plan, the candidate ranks products by contribution per unit sold instead of contribution per unit of the scarce resource.
Contribution per unit is the number drilled into them in earlier absorption-vs-marginal questions, and the metric 'per unit' feels like the natural ranking basis; candidates do not re-read what is actually scarce.
What to do instead
Before ranking, write down the scarce resource and its units per product. Convert each product's contribution to contribution per unit of that resource, rank on that, then allocate the resource in rank order and check the remaining resource after each product.
On a make-or-buy question, the candidate compares the external purchase price with total absorption cost per unit rather than with the relevant (avoidable) cost.
Total cost per unit is the figure sitting in the cost card, so it is the number to hand; candidates forget that apportioned fixed overheads often continue whether or not the item is made.
What to do instead
Build a relevant-cost schedule: variable costs plus any specific avoidable fixed costs, and exclude apportioned general fixed overhead. Compare that avoidable total with the buy price, and add opportunity cost if internal capacity has an alternative use.
When a question supplies a learning curve, the candidate applies the curve to every unit produced, including units after the learning period, or applies the cumulative average time to the marginal unit.
The doubling formula gives a cumulative average, and the distinction between cumulative average time, total time and incremental time per unit is easy to blur under time pressure.
What to do instead
State which measure the formula produces (cumulative average time per unit at the doubled cumulative output). Derive total time as average x cumulative units, and get the time for the next batch by differencing two cumulative totals. Stop applying learning once steady state is reached.
The candidate computes a variance and stops, without stating whether it is adverse or favourable or explaining the likely operational cause.
The arithmetic feels like the answer, and the sign convention (standard minus actual for cost variances) is applied mechanically without interpretation.
What to do instead
For every variance, write one line: name, amount, A/F, and one plausible cause tied to the scenario (e.g. cheaper material from a new supplier, more skilled labour). Check the direction against the definition before moving on.
The candidate calculates planning and operational variances by mixing up which variance uses the original standard and which uses the revised standard.
Both variances compare standard to actual, and the only difference is which standard; candidates do not label the standards before starting.
What to do instead
Write two columns headed 'original standard' and 'revised standard' before calculating. Planning variance = original vs revised standard. Operational variance = revised standard vs actual. Keep the two comparisons physically separate on the page.
On a mix and yield variance question, the candidate calculates a simple usage variance or applies mix proportions to total actual input without weighting by standard cost.
Mix and yield are only relevant when inputs are substitutable, and the weighted-average standard cost step is easy to skip.
What to do instead
Confirm inputs are substitutable. Calculate the weighted average standard cost of the standard mix. Mix variance uses the difference between actual and standard mix at actual total input; yield variance uses the difference between actual total input and standard input for actual output. Value both at the weighted average standard cost.
When preparing a cash budget, the candidate includes depreciation, or includes costs at the point they are incurred rather than when cash moves, and omits the timing of receipts from credit customers.
Candidates carry over the accruals mindset from profit statements and treat the cash budget as an income statement with a closing balance.
What to do instead
Go through each line and ask 'does cash move, and when?'. Strip out non-cash items such as depreciation and provisions, apply the stated credit terms to sales and purchases, and include capital expenditure, tax and dividend payments at their actual payment dates.
The candidate calculates a return on investment or residual income figure and then draws a divisional performance conclusion without considering controllability or the different behavioural incentives of the two measures.
The calculation is the visible task, and the discussion marks are treated as optional padding rather than a required part of the answer.
What to do instead
After the numbers, add a short paragraph: which items the manager controls, whether ROI encourages rejecting projects below current ROI but above cost of capital, and how RI avoids that. Tie the conclusion to the specific figures calculated.
Given a balanced scorecard or performance pyramid scenario, the candidate lists generic measures (profit, sales) against each perspective instead of measures that fit the named perspective and the organisation in the scenario.
Candidates memorise perspective names but not the logic of cause and effect, so they default to financial measures everywhere.
What to do instead
For each perspective, ask what the perspective is trying to achieve and pick a measure that would actually move it (e.g. customer retention for customer, defect rates and cycle time for internal process, staff training hours and retention for learning and growth). Justify each measure in one clause linked to the scenario.
In a written section, the candidate writes a general essay on the technique (e.g. 'advantages and disadvantages of ABC') without applying it to the figures or circumstances in the scenario.
Under time pressure, candidates reproduce memorised textbook lists because it feels safer than interpreting the data given.
What to do instead
Read the requirement verbatim and count the marks to infer the number of points needed. Anchor every point to a named figure, department or fact from the scenario, and reserve the last few minutes to check each paragraph mentions the scenario.