Audit and Assurance · Automated tools and techniques

Computer-Assisted Audit Techniques (CAATs) for ACCA AA

Updated 11 October 2026 · Fact-checked

CAATs are audit procedures that use computers to test a client's systems and data. The two main types are test data, which checks that programs process transactions correctly, and audit software, which analyses the client's files. To answer questions, name the technique, say what it tests, and give a benefit and a limit.

Understand Computer-Assisted Audit Techniques (CAATs)

A computer-assisted audit technique (CAAT) is any use of computer technology by the auditor to gather audit evidence. Many clients keep records in electronic form. Often a person cannot check every item by hand. A computer can.

There are two main types in the AA syllabus.

Audit software is a program that reads the client's data files. It can recalculate balances, sort and filter items, compare files, look for duplicates or gaps in number sequences, select samples and produce reports. It mainly gives substantive evidence about the data. Examples include recalculating receivables ageing, finding duplicate supplier payments and listing journals posted at unusual times.

Test data means the auditor submits dummy transactions to the client's system and compares the system's output with results the auditor expected. It mainly tests controls inside the program, such as validation checks, limit checks and authorisation rules. Include both valid and invalid items. Valid items should be accepted. Invalid items, such as a wrong date or an order over the credit limit, should be rejected. Test data is therefore mostly a test of controls.

CAATs are used when the client has a complex or high-volume system, when there is little paper trail, or when the auditor wants to test a whole population instead of a sample. They also have costs and risks. These include setup cost, the need for IT skills, and the danger of corrupting live data. Good planning keeps these risks under control.

Key rules to remember

Audit software: Audit software = programs run on the client's live data files; Mainly substantive procedures: recalculation, sorting, matching, duplicate and gap testing, sample selection.
Test data: Test data = dummy transactions (valid + invalid) processed by the client's system, results compared with expectations; Mainly tests of controls. Use dummy data on a copy of the system where possible, or reverse the entries, so live records are not corrupted.
Reliability check: Result is reliable only if the program tested is the program used all year; Test data tests the system at one point in time. The auditor must be satisfied that no program changes were made afterwards.

How to solve Computer-Assisted Audit Techniques (CAATs) questions

Use this method for any question on CAATs, whether it asks for uses, advantages, disadvantages or the choice of technique.

1Read the requirement and note the verb: explain, describe, list, or evaluate. This sets the depth of your answer.
2Name the technique asked for: audit software or test data. If the scenario fits one, choose it and say why.
3State what it does in one clear sentence. For audit software say it analyses data. For test data say it checks that program controls work.
4Link it to the scenario: the system, the volume of data, the account or control being tested, and the assertion covered.
5Give specific procedures, such as recalculating, finding duplicates, checking gaps in sequence, or entering invalid dummy items.
6Add a limit or risk that fits the scenario, such as cost, skills needed, corrupting live data, or testing only at one point in time.
7Finish with the effect on the audit: more coverage, better evidence, or less sampling.

Quickest way: Data or controls?

When to use it: Use this for a short objective test question that asks which CAAT is suitable or what a CAAT does.

Ask: is the task about the data in the files, or about whether the program's controls work?
Data in the files (totals, duplicates, ageing, gaps, selecting samples): audit software.
Controls inside the program (rejecting invalid items, authorisation, limits): test data.
Check the wording. 'Dummy transactions' always means test data. 'Analyse the client's file' means audit software.
Eliminate options that suggest CAATs replace the auditor's judgement or remove all risk. They do not.

Common mistakes in Computer-Assisted Audit Techniques (CAATs)

Confusing test data with audit software.
Both use computers, so students treat them as the same thing.
Fix: Remember: test data puts dummy items in to test controls. Audit software takes the real data out to analyse it.
Saying CAATs replace the auditor's judgement.
Students assume automation does the thinking.
Fix: Say that the auditor still plans the work, designs the tests, interprets exceptions and concludes.
Listing only advantages.
Students focus on speed and coverage.
Fix: Always add limits: setup cost, IT skills, risk of corrupting live data, and compatibility with the client's system.
Stating that test data tests the whole year.
Students forget that it runs at one point in time.
Fix: Add that the auditor must confirm the program was not changed after the test, or must rerun the test.
Giving generic points not linked to the scenario.
Students recite a memorised list.
Fix: Name the client's system, the account and the specific procedure, such as testing the receivables ledger for balances over the credit limit.
Using dummy data on the live system without protection.
Students overlook the effect on real records.
Fix: Say the auditor should use a copy of the system or reverse the dummy entries, so that live files are not corrupted.

Worked examples

Example 1

You are auditing a retailer with a high-volume computerised sales ledger. Describe how audit software could be used to obtain evidence on receivables. (6 marks)

Show the solution

Name the technique: audit software run on the receivables ledger file. It gives substantive evidence.
Recalculate the ledger total and agree it to the control account in the trial balance. This tests accuracy.
Produce an ageing analysis and list old balances. This helps test valuation and the allowance for credit losses.
List balances over the customers' credit limits and unusual credit balances for follow-up.
Check for duplicate invoice numbers and gaps in the invoice sequence. This tests occurrence and completeness.
Select a sample of balances for the receivables confirmation. Note the limit: the auditor needs IT skills and must be sure the file is complete and is the live ledger.

Answer: Audit software can recalculate and agree the ledger to the control account, age balances, flag items over credit limits, find duplicates and sequence gaps, and select a sample for confirmation. It gives broad coverage but needs IT skills and assurance that the data file is complete and live.

Example 2

An auditor plans to use test data on a client's payroll program. Explain what test data is, what it should include, and two limits. (5 marks)

Show the solution

Define: the auditor enters dummy transactions into the client's system and compares the output with expected results.
Purpose: it tests that controls in the program work, so it is a test of controls.
Include valid items, which should be accepted. Include invalid items, such as an employee number that does not exist, hours above a set limit, or a missing authorisation. These should be rejected.
Limit one: it tests the program at one point in time. The auditor must confirm there were no later program changes.
Limit two: dummy data can corrupt live files unless a copy of the system is used or the entries are reversed. It also needs IT skills and time to design.

Answer: Test data is dummy transactions, valid and invalid, processed by the client's payroll program to check that its controls accept correct items and reject incorrect ones. Limits: it tests only at one point in time, and it risks corrupting live data and needs IT skills.

Exam tips

Match the technique to the task: data analysis points to audit software, and testing program controls points to test data.
In written answers, always tie the CAAT to a specific account, control or assertion in the scenario.
Give both advantages and disadvantages when the verb is 'evaluate' or 'discuss'.
Objective questions are all or nothing, so check the wording for 'dummy transactions' or 'analyse files' before choosing.
Show a brief answer layout in Section C: technique, procedure, benefit, limit.

Computer-Assisted Audit Techniques (CAATs) in other exams

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

Computer-Assisted Audit Techniques (CAATs): frequently asked questions

What are CAATs in audit and assurance?

CAATs are computer-assisted audit techniques. They are audit procedures that use computer tools to test the client's systems and data. The main types are audit software and test data.

What is the difference between test data and audit software?

Test data enters dummy transactions to check that the client's program controls work. Audit software runs on the client's real data to recalculate, sort, match and analyse. Test data is mostly a test of controls, and audit software is mostly substantive.

What are the advantages and disadvantages of CAATs?

Advantages include testing large volumes of data, wider coverage than sampling, speed and consistency. Disadvantages include setup cost, the need for IT skills, the risk of corrupting live data and problems with compatibility. The auditor must also confirm the data is complete and reliable.

Do CAATs replace manual audit work?

No. The auditor still plans the tests, follows up exceptions and reaches conclusions. CAATs make some procedures faster and broader but do not remove the need for judgement.