Internal and Forensic Audit · Practices related to Internal Auditing

Internal Audit Engagement and Fieldwork Explained

Updated 11 October 2026 · Fact-checked

An internal audit engagement is a single assignment carried out from entry meeting to closing. Fieldwork is the execution stage: you walk through processes, select samples, test controls, collect evidence and record everything in working papers. Answer exam questions by following that sequence and tying each step to the audit objective.

Understand Internal Audit Engagement and Fieldwork

An engagement is one internal audit assignment, such as an audit of the procurement cycle at a plant. It has a start, a defined scope and a report. Planning decides what to audit. Fieldwork is where you actually do the audit.

Fieldwork usually starts with an entry (opening) meeting with the auditee. You confirm the objectives, scope, timing, contact persons and the information you need. Then you perform process walkthroughs. You trace one transaction from start to finish, for example a purchase requisition through to payment. You talk to the people who do the work and look at the documents. This confirms that the process on paper is the process in practice.

Next you test. You cannot check every transaction, so you select a sample. Sampling can be statistical (random selection, with results projected to the population using probability) or non-statistical (judgmental, based on risk, value or unusual items). You then perform tests of controls (does the control operate?) and, where needed, substantive tests (are the amounts or records right?).

What you collect to support your conclusions is audit evidence. It should be sufficient, relevant, reliable and useful. Common methods are inspection, observation, inquiry, confirmation, re-performance, recalculation and analytical review. Evidence from outside the entity, or obtained directly by you, is generally more reliable than what the auditee tells you.

Working papers are your record of the work: the plan, programme, tests done, evidence examined, findings and conclusions. Evidence is the material you gather. Working papers are the file in which you document it and your reasoning. A reviewer should be able to understand your work without asking you.

Key rules to remember

Sampling interval (systematic selection): Sampling interval = Population size ÷ Sample size; Pick a random start within the first interval, then every nth item. Example: 1,000 invoices, sample 50, interval 20.
Sampling risk (conceptual): Larger sample → lower sampling risk, but more time and cost; Sampling risk is the risk that the sample conclusion differs from the conclusion on testing the whole population.
Test of controls vs substantive test: Test of controls = does the control operate? Substantive test = is the balance or transaction correct?; Keep the two purposes separate in answers.
Attributes of good evidence: Sufficient + Relevant + Reliable + Useful; Sufficiency is about quantity. Relevance, reliability and usefulness are about quality.
Deviation rate: Deviation rate = Number of deviations ÷ Sample size × 100; Compare it with the tolerable deviation rate set in planning.

How to solve Internal Audit Engagement and Fieldwork questions

Use this order for any question on engagement conduct, fieldwork, sampling, evidence or working papers.

1Identify the stage the question is about: entry meeting, walkthrough, sampling, testing, evidence or documentation.
2State the objective of that stage in one line, linking it to the engagement scope and risks.
3Describe the procedure in order, using the facts given in the case, such as the entity, process and amounts.
4Name the technique or method used, such as random or judgmental sampling, inspection, re-performance or confirmation.
5Say how the result is recorded in working papers: source, procedure, sample, findings, conclusion, preparer and reviewer.
6Conclude: say what the auditor does with exceptions, such as extending samples, discussing with the auditee and reporting.

Quickest way: Stage, purpose, method, record

When to use it: Use it for short-note questions or when time is tight in a case-based answer.

Write the stage name and its purpose in one sentence.
List three to four procedures or techniques in bullets.
Add one line on documentation in working papers.
Close with one line on how exceptions are handled or escalated.

Common mistakes in Internal Audit Engagement and Fieldwork

Treating audit evidence and working papers as the same thing.
Both relate to supporting the audit conclusion, and textbooks use them close together.
Fix: Say evidence is the information obtained, and working papers are the auditor's record of procedures, evidence examined and conclusions.
Skipping the walkthrough and going straight to sampling.
Students see testing as the real work.
Fix: Explain that the walkthrough confirms how the process really operates, so you can design relevant tests and spot control gaps.
Saying statistical sampling is always better than judgmental sampling.
Statistical methods sound more scientific.
Fix: State the trade-off. Statistical sampling allows measuring sampling risk and projection. Judgmental sampling suits risk-focused selection but cannot be projected statistically.
Relying only on inquiry as evidence.
Asking the auditee is quick and easy.
Fix: Say that inquiry alone is weak. Corroborate with inspection, observation, re-performance or external confirmation.
Leaving working papers incomplete or unreviewed.
Students focus on the report and treat documentation as an afterthought.
Fix: Mention preparer sign-off, date, source references, conclusions and supervisory review as essential elements.
Ignoring exceptions found in the sample.
Students assume one error is immaterial.
Fix: Show the response: investigate the cause, assess the effect, consider extending the sample, and report significant findings.

Worked examples

Example 1

During fieldwork on the purchase cycle of Bharat Components Ltd, you must test whether goods are received before invoices are approved. The population is 2,400 purchase invoices. You decide on a systematic sample of 60. Explain how you select the sample and the next steps of testing.

Show the solution

Compute the sampling interval: 2,400 ÷ 60 = 40.
Choose a random starting point between 1 and 40, say 17.
Select invoices numbered 17, 57, 97 and so on, every 40th item, until 60 items are selected.
For each selected invoice, inspect the goods received note, the purchase order and the approval date to check that receipt preceded approval.
Record each item tested, the result and any deviation in the working paper.
If you find 3 deviations, the deviation rate is 3 ÷ 60 × 100 = 5%. Compare it with the tolerable rate set in planning and decide on further testing and reporting.

Answer: The sampling interval is 40. Select every 40th invoice from a random start, test each against the goods received note and purchase order, document the results, and compare any deviation rate with the tolerable rate before concluding.

Example 2

Distinguish audit evidence from working papers, and explain what a working paper for a bank reconciliation test should contain.

Show the solution

Define audit evidence: the information the auditor obtains to support findings and conclusions, such as bank statements, confirmations and recalculations.
Define working papers: the auditor's record of the work done, the evidence examined and the conclusions reached.
Point out the relationship: evidence is the input, and working papers document how it was obtained and used.
List the content of the bank reconciliation working paper: title, entity, period, objective and preparer's name and date.
Add the source of data, such as the bank statement and cash book, the procedure performed such as recalculation and tracing of reconciling items to subsequent clearing.
Add the exceptions noted, such as stale cheques, the conclusion, the cross-reference to the audit programme, and the reviewer's sign-off.

Answer: Evidence is what you gather. Working papers are the file recording your procedures, the evidence and your conclusions. The bank reconciliation paper should show objective, source, procedures, exceptions, conclusion and review sign-off.

Exam tips

Follow the sequence entry meeting, walkthrough, sampling, testing, evidence, working papers, and use it as your answer skeleton.
In case-based questions, name the exact technique and link it to the facts given, for example inspection of goods received notes.
When asked to differentiate evidence from working papers, define both and add one example of each.
Show the sampling interval or deviation rate calculation when numbers are given, and state the conclusion.
Mention supervisory review of working papers; many answers lose marks by omitting it.

Practice questions from Practices related to Internal Auditing

Internal Audit Engagement and Fieldwork in other exams

The same ground in other exams, if you are preparing for more than one or want another angle on it.

Internal Audit Engagement and Fieldwork: frequently asked questions

What is the difference between audit evidence and working papers?

Audit evidence is the information the auditor gathers to support conclusions. Working papers are the record of the procedures performed, the evidence examined and the conclusions drawn. Evidence goes into the working papers.

Why is a process walkthrough done before testing?

A walkthrough shows how a process works in practice by tracing one transaction end to end. It helps you find where controls exist or are missing and design tests that match the real process.

Which sampling method should an internal auditor use?

It depends on the objective. Use statistical sampling when you want to measure sampling risk and project results. Use judgmental sampling when you want to focus on high-risk, high-value or unusual items.

What should good internal audit working papers contain?

They should show the objective, scope, procedures, sample, evidence examined, findings, conclusions, cross-references, and the preparer and reviewer sign-offs with dates.