“This client’s revenue has gone up, but so has its gross margin, and by much more: what do you make of that?” This question, or one of its variants, comes up in many interviews at audit firms. It does not test your ability to recite a standard, but the way you reason when faced with accounts you do not know. Firms use these short case studies because they resemble the real work of an audit assistant: spotting what does not add up, forming a hypothesis, knowing which document to ask for. This article describes the formats you may encounter, proposes a four-step answer method, then works through three solved cases.
Why firms set a case study
A CV says what you have done; a case shows how you think. For an audit recruiter, three things are hard to read on a CV and easy to observe in twenty minutes of a case:
- the reflex of questioning a figure, which the standards call professional scepticism;
- the ability to link the financial statements together: a change in margin points to inventory, purchases and sales;
- moving from analysis to action: which audit procedure would allow you to resolve the doubt.
The French professional auditing standards (normes d’exercice professionnel, NEP) that govern the certification of financial statements require the statutory auditor to plan and perform the audit with professional scepticism, to assess the risk of material misstatement, including misstatement due to fraud, and to gather sufficient appropriate evidence. An interview case is a scaled-down version of that approach.
The formats you may encounter
Formats vary with the size of the firm and the level of the position.
The oral case during the interview. The recruiter or manager describes a situation in a few sentences, sometimes with an extract from an income statement, and asks you to think out loud. This is the most common format for internships and first jobs, including for a work-study placement in an accounting firm, where the exercise remains simpler.
The timed written case. You are given a file of a few pages (trial balance, account extracts, notes) to analyse in thirty to sixty minutes, then you present your conclusions. This format is common at the recruitment days of large networks and for experienced profiles.
The spreadsheet exercise. Rarer, it involves working on an extract from a general ledger or a file of journal entries to draw out an analysis: duplicates, unusual entries, reconciliation. It tests both technique and ease with tools.
The judgement case. At senior level, the case covers an area of estimation (a litigation provision, the impairment of an asset) and aims to see whether you know how to assess a management assumption.
A four-step answer method
Whatever the format, a simple structure stops you from heading off in every direction.
- Rephrase and frame. Repeat the question in your own words, then ask one or two context questions: the client’s sector, size, year-end date, what changed during the year. This shows that you are not applying a ready-made answer.
- Form hypotheses. List the possible explanations, from the most ordinary to the most worrying. A rise in margin may come from a price change, a product mix, a fall in purchase costs… or an error in inventory valuation.
- Link to the accounts and the risks. For each hypothesis, say which item in the accounts it affects and which assertion would be at stake: existence, completeness, valuation, cut-off.
- Propose procedures. Finish with what you would do in the field: which document to request, which test to perform, whom to ask at the client.
The recruiter assesses the approach more than the “right answer”. A candidate who proposes two hypotheses clearly linked to concrete tests makes a better impression than one who cites ten without knowing how to check them.
Three cases worked through step by step
Case 1: a gross margin that rises without explanation
Facts. An SME distributing electrical equipment sees its revenue rise by 4% over the year, while its gross margin rate goes from 28% to 35%. Management talks about an “exceptional year”.
Rephrase and frame. The margin is rising much faster than activity. Context questions: have selling prices been increased? Has the main supplier changed? Has there been a change in the stock-count method?
Hypotheses. Higher selling prices not matched by purchase costs; better purchasing terms (year-end rebates); a shift in mix towards more profitable products; but also an overstatement of closing inventory, which mechanically reduces cost of sales, or year-end purchases not recorded.
Link to the accounts. The margin depends on sales, purchases and the change in inventory. The two worrying hypotheses affect the valuation and existence of closing inventory, and the completeness of purchases.
Procedures. Analytical review of the margin by product family and by month; reconciliation of closing inventory with the physical count and a valuation test on a sample of items; cut-off testing on late-December goods received and January supplier invoices; review of supplier rebates and their contractual support.
Case 2: inventory to be valued
Facts. An industrial client holds in stock a batch of components purchased for a product whose sale has just been discontinued. The batch is recorded at its purchase cost.
Rephrase and frame. The question is one of impairment. Context: can the component be used for other products? Is there a resale market? What is the client’s impairment policy?
Hypotheses. If the component has no further use or outlet, its current value is probably below cost, and an impairment is needed. If it can be reused, a partial impairment, or none at all, may be justified.
Link to the accounts. The French chart of accounts (plan comptable général) defines the impairment of an asset as the recognition that its current value has fallen below its net book value, and states that inventories are valued taking account of prices and sales prospects. The assertion at stake is valuation.
Procedures. Interview with the production management about possible uses; review of the component’s consumption over recent months and of orders in progress; search for resale prices or buy-back offers; comparison with the impairment policy for slow-moving items; check for consistency with the treatment in prior years.
Case 3: a suspicious entry
Facts. While testing journal entries, you find a manual entry posted on 31 December at 11 pm by an administrative manager, for a round amount, crediting an expense account and debiting a prepaid expenses account, described as “adjustment”.
Rephrase and frame. Several warning signs combine: manual entry, year-end date, unusual time, round amount, vague description, a user who does not usually post entries. Context: does the client have profit targets linked to bonuses or bank covenants?
Hypotheses. A legitimate but poorly documented adjustment; an error; or manipulation intended to improve the year’s profit by deferring an expense to the following year.
Link to the accounts. The risk concerns cut-off and the reality of the prepaid expenses. The standards require the auditor to consider the possibility of fraud, in particular management override of controls, and to test journal entries.
Procedures. Request the supporting document for the entry and the name of the person who authorised it; analyse the underlying invoice or contract to check the period of consumption; search for other entries with the same profile; check for any reversal at the start of the following year; inform the audit senior if the doubt remains.
What the recruiter really assesses
At the end of a case, the recruiter does not keep a mark but an impression built on a few criteria:
- structure: did you follow a thread, or jump from one idea to the next?
- vocabulary: do you talk about assertions, cut-off, analytical review, external confirmations, without overdoing it?
- practical sense: are your procedures feasible at a real client, in a few hours?
- humility: can you say “I would ask my audit senior” rather than invent a certainty?
- communication: one day a client will have to hear your questions; tone matters.
A useful point of comparison: strategy consulting cases follow a different logic, centred on a business recommendation and an issue-tree structure. If you are also preparing for that kind of interview, the article on the profitability case in case interviews 🔗 shows the difference in approach. In audit, the conclusion is not a strategy but a verification procedure.
Linking the case to the experience on your CV
The case is also a chance to bring your CV to life. If you took part in physical stock counts, external confirmations or cut-off tests during a busy season, say so when you propose your procedures: “during my busy season, I carried out this type of test on year-end goods received”. That turns a theoretical answer into proof of experience.
Your CV still needs to show it. A vague line such as “took part in audit engagements” gives you nothing to talk about; a precise line gives you examples. Our article on how to describe your audit engagements on a CV gives before/after wording, and the general audit CV method details the structure. The audit assistant CV example shows how busy-season tasks are described with volumes.
Once your CV has been rewritten in this spirit, the CV editor takes care of the formatting: one column, standard sections and a PDF that firms’ screening software reads correctly, so that your experience makes it through to the interview where you can talk about it.
Sources
- Haute Autorité de l’audit, the professional standards framework for statutory auditors 🔗.
- Légifrance, order of 13 November 2024 approving eleven revised professional auditing standards 🔗.
- Autorité des normes comptables, French chart of accounts, version as at 1 January 2026 🔗.
Frequently asked questions
Do you need to know the standards by heart to succeed in a case?
No. A junior candidate is expected to know the main principles (professional scepticism, the risk-based approach, assertions) and to be able to propose tests. Citing a specific standard is a plus, not a requirement.
How long does a case study last in an interview?
An oral case generally takes between ten and twenty minutes. A written case is done in thirty to sixty minutes, followed by a presentation.
What should you do if you do not know the client’s sector?
Say so and ask questions. The recruiter assesses your approach: a candidate who asks how the client sets its prices or manages its inventory is showing exactly the reflex expected.
Can you practise on your own?
Yes, by taking published accounts, looking for the largest changes from one year to the next, then applying the four-step method. Practising out loud helps a great deal for the oral format.