Advanced Audit and Assurance (International) · The assurance of sustainability

Planning, Evidence and Reporting on Sustainability Assurance

Updated 11 October 2026 · Fact-checked

Sustainability assurance is an engagement where a practitioner gives a conclusion on sustainability information, such as carbon emissions, against suitable criteria. You plan around risk and materiality, gather sufficient appropriate evidence on the data and its systems, use experts where needed, and issue a report with a clear conclusion.

Understand Planning, Evidence and Reporting on Sustainability Assurance

Sustainability information is mostly non-financial. Examples are carbon emissions, energy use, water use, staff turnover and injury rates. Companies publish it in sustainability reports. Users rely on it, so they want independent assurance that it is reliable.

The work is an assurance engagement, not an audit of financial statements. It follows ISAE 3000 (Revised) or ISSA 5000, which is the dedicated sustainability assurance standard. The same structure applies as in any assurance engagement: practitioner, responsible party, intended users, subject matter, suitable criteria, evidence and a report.

Criteria come first. Without suitable criteria you cannot form a conclusion. Suitable criteria are relevant, complete, reliable, neutral and understandable. A recognised framework, such as the GHG Protocol for emissions, usually meets this. If management invents its own measures, you must judge whether they are suitable and whether they are disclosed clearly to users. Weak criteria can mean you should decline the engagement or modify the conclusion.

Planning is risk-based. You assess the risk that the information is materially misstated. Materiality may be quantitative (a percentage error in tonnes of CO2e) and qualitative (a missed regulatory limit, or a misstatement that hides a trend users care about). Key risks include estimation uncertainty, manual data collection, many sites, weak controls over data, and greenwashing. Greenwashing is where the report gives a misleadingly positive picture of environmental performance, through selective disclosure, vague claims, or unsupported targets. It is a risk of material misstatement and also an ethical and reputational risk for you.

Evidence comes from tracing data to source, testing controls over data capture, recalculating, analytical review and checking to external records. Experts, such as engineers or emissions scientists, may be needed. You must assess their competence, capability and objectivity, and evaluate their work. You can give limited assurance (negative-form conclusion, fewer procedures) or reasonable assurance (positive-form conclusion, more extensive procedures). The report states which one, the criteria, the responsibilities of each party and the conclusion.

Key rules to remember

Suitable criteria: Relevant + Complete + Reliable + Neutral + Understandable; Use as a checklist when asked whether management's measures are suitable. Mention disclosure of the criteria to users.
Reasonable assurance conclusion: "In our opinion, the subject matter information is prepared, in all material respects, in accordance with the criteria."; Positive form. Requires more extensive procedures than limited assurance.
Limited assurance conclusion: "Nothing has come to our attention that causes us to believe the subject matter information is not prepared, in all material respects, in accordance with the criteria."; Negative form. Fewer procedures, so a lower level of assurance.
Expert evaluation: Competence + Capabilities + Objectivity, then evaluate the work; Using an expert does not reduce your responsibility for the conclusion.
Report content: Title, addressee, criteria and subject matter, responsibilities, standard followed, independence and quality management, procedures summary, conclusion; Reports must also state the level of assurance. Limited assurance reports describe procedures more fully.

How to solve Planning, Evidence and Reporting on Sustainability Assurance questions

Use this order for any exam question on planning, evidence or reporting for sustainability assurance. Tie each point to the scenario.

1Identify the subject matter, the responsible party and the intended users from the scenario.
2Judge whether the criteria are suitable and available to users. Name the failed attribute if not.
3Decide the level of assurance (limited or reasonable) and what it means for procedures and wording.
4Set materiality using quantitative and qualitative factors, and list risks such as estimation, weak data controls, multiple sites and greenwashing.
5Design evidence procedures for the data: source tracing, controls testing, recalculation, analytics and external corroboration.
6Consider experts: need, competence, objectivity, and how you will evaluate the work.
7State the report conclusion and any modification, with reasons linked to the facts.
8Add professional skills points: scepticism, commercial awareness and clear, concise communication.

Quickest way: Criteria, Risk, Evidence, Report

When to use it: Use when time is short and the requirement asks for procedures, risks or the report in one question.

Write four headings: Criteria, Risks, Evidence, Report.
Under Criteria, note one point on suitability from the scenario.
Under Risks, list two or three scenario-specific risks, including greenwashing if claims are vague.
Under Evidence, give one procedure per risk, naming the document or test.
Under Report, state the assurance level and the conclusion type, then explain any modification.

Common mistakes in Planning, Evidence and Reporting on Sustainability Assurance

Treating the engagement like a financial statement audit and giving a reasonable assurance audit opinion by default.
Students are used to ISA 700 wording.
Fix: Check the level of assurance in the scenario. Use ISAE 3000 or ISSA 5000 language and the correct form of conclusion.
Ignoring whether criteria are suitable.
Students jump straight to procedures.
Fix: Start with criteria. Test them against relevant, complete, reliable, neutral and understandable, and say whether users can access them.
Listing generic procedures such as inspect and enquire with no link to the data.
It is a safe pattern from financial audit papers.
Fix: Name the data: for emissions, trace fuel and electricity usage to invoices and meter readings, apply the emission factor and recalculate.
Setting materiality only as a percentage.
Financial audit habits carry over.
Fix: Add qualitative factors, such as legal limits, targets, trends and what users are most interested in.
Saying the expert's report removes your responsibility.
Students confuse reliance with delegation.
Fix: State that you remain responsible for the conclusion. Assess the expert's competence, capabilities and objectivity and evaluate their work.
Missing greenwashing signals such as vague claims, selective data or unsupported net-zero targets.
Students focus on number errors.
Fix: Read the other information and claims for balance. Challenge whether claims are supported, and consider a modified conclusion or withdrawal if management will not correct them.

Worked examples

Example 1

You are the practitioner on a limited assurance engagement on a manufacturer's reported Scope 1 and 2 emissions of 48,000 tonnes CO2e for the year. Operations are at 12 sites and data is collected on spreadsheets by site managers. Explain the key evidence procedures you would perform. (8 marks)

Show the solution

Identify risk: manual spreadsheets, 12 sites and possible inconsistent emission factors create a risk of material misstatement.
Obtain the boundary and criteria (for example the GHG Protocol) and check that all 12 sites and relevant sources are included.
Understand the data process and test controls over capture and consolidation, including who reviews site spreadsheets.
Trace a sample of fuel and electricity quantities to invoices, meter readings and supplier statements.
Check the emission factors used against published sources and recalculate the emissions for a sample of sites.
Recalculate the consolidation and compare to the reported total of 48,000 tonnes.
Perform analytical procedures: compare sites with prior year and with production levels, and investigate unusual movements.
Make enquiries of management on changes in operations, and obtain written representations.

Answer: Focus on the boundary, source data, emission factors, recalculation and analytics, because manual spreadsheets across 12 sites are the main risk. Because it is limited assurance, procedures are mainly enquiry, analytics and targeted testing rather than extensive detailed testing.

Example 2

A company's sustainability report states "we are leading the sector in reducing our environmental impact" and shows only the three metrics that improved. Management refuses to add a metric that worsened. You are the engagement partner. Discuss the issue and the report implications. (6 marks)

Show the solution

Identify the issue: selective disclosure and an unsupported claim suggest greenwashing.
Assess the criteria: if they require complete and neutral information, omitting the adverse metric breaches them.
Evaluate materiality: the omitted metric is likely qualitatively material because users would find it relevant to a judgement of the claim.
Request management to include the metric and support or remove the claim. Document the discussion with those charged with governance.
If refused, consider the effect on the conclusion: a qualified or adverse conclusion, depending on how pervasive the issue is.
Consider ethical and reputational risk, and whether withdrawing from the engagement is appropriate if integrity is in doubt.

Answer: The omission and unsupported claim are a material misstatement against criteria that require completeness and neutrality. If management will not correct them, modify the conclusion (qualified, or adverse if pervasive) and explain the basis. Consider withdrawal if management's integrity is in doubt.

Exam tips

Always link procedures to the specific data in the scenario, such as meter readings, fuel invoices or HR records.
Mention the level of assurance and how it changes procedures and wording. Many candidates skip this.
Where the scenario has vague claims or selective data, say greenwashing and explain the effect on the conclusion.
For the report, give the structure and the conclusion, and explain any modification with reasons.
Earn professional skills marks by challenging management claims and keeping answers short, structured and commercial.

Practice questions from The assurance of sustainability

Planning, Evidence and Reporting on Sustainability Assurance in other exams

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

Planning, Evidence and Reporting on Sustainability Assurance: frequently asked questions

What evidence do I need for carbon emissions data?

Trace activity data such as fuel and electricity use to invoices and meter readings, check emission factors to published sources, and recalculate. Test controls over data collection and consolidation. Use analytics to compare with prior year and activity levels.

What is the difference between limited and reasonable assurance?

Reasonable assurance is high, with more extensive procedures and a positive-form conclusion. Limited assurance is meaningful but lower, with fewer procedures and a negative-form conclusion. The report must state which one was given.

How does greenwashing affect the assurance engagement?

It is a risk of material misstatement because the report may mislead users through selective or unsupported claims. You challenge the claims, assess completeness and neutrality against the criteria, and modify the conclusion if management will not correct them.

Can I rely on an expert in sustainability assurance?

Yes, but you remain responsible for the conclusion. You assess the expert's competence, capabilities and objectivity, agree the scope of work, and evaluate whether the work is adequate for your purpose.