Environmental, Social and Governance (ESG) reporting is becoming an increasingly important part of corporate reporting. Companies are disclosing information about greenhouse-gas emissions, energy consumption, workforce practices, diversity, safety, governance, climate risks, sustainability targets and other ESG matters.

But an important question follows:

Can investors, regulators, lenders and other stakeholders trust the information being reported?

This is where ESG assurance becomes important.

ESG assurance is the independent evaluation of sustainability-related information to provide confidence that reported information has been prepared in accordance with applicable criteria and is supported by appropriate evidence.

The International Sustainability Standards Board (ISSB) has designed IFRS S1 and IFRS S2 so that reported sustainability-related financial information is capable of being assured, although the IFRS Foundation itself does not mandate assurance; the level and timing of assurance are determined by individual jurisdictions.

For India, an important development came in September 2026 when the Institute of Chartered Accountants of India (ICAI) issued SSA 5000 – General Requirements for Sustainability Assurance Engagements. The standard provides a principles-based, framework-neutral approach and is effective for sustainability assurance engagements relating to periods beginning on or after 1 April 2027.

1. What Is ESG Assurance?

ESG assurance is a professional engagement designed to increase confidence in sustainability information.

The information being assured may include:

• Greenhouse-gas emissions
• Energy consumption
• Water consumption
• Waste
• Employee data
• Workplace safety
• Diversity
• Human-rights indicators
• Supply-chain information
• ESG targets
• BRSR information
• Climate-related disclosures
• Sustainability KPIs

The assurance practitioner evaluates whether the information has been prepared against appropriate criteria and whether sufficient appropriate evidence supports the conclusion.

In simple terms:

ESG Reporting = What the company reports

ESG Assurance = Independent confidence in what the company reports

2. Why Is ESG Assurance Important?

Sustainability information can influence important decisions.

Investors may use it to evaluate companies.

Banks may consider climate and ESG risks.

Customers may assess suppliers.

Employees may consider sustainability performance.

Regulators may use disclosures for supervision.

If the information is inaccurate, incomplete or misleading, decisions can be affected.

Assurance therefore helps improve:

• Trust
• Reliability
• Transparency
• Accountability
• Data quality
• Comparability
• Stakeholder confidence

3. ESG Reporting vs ESG Assurance

These are two different responsibilities.

ESG Reporting

The company:

• Collects data
• Calculates metrics
• Sets targets
• Prepares disclosures
• Approves the report

ESG Assurance

The assurance practitioner:

• Evaluates the criteria
• Assesses risks
• Tests evidence
• Evaluates controls
• Performs procedures
• Reaches an assurance conclusion

The company remains responsible for its reported information.

The assurance practitioner does not become the owner of management’s ESG data.

4. What Information Can Be Assured?

Depending on the applicable requirements, assurance may cover:

Environmental Information

• Scope 1 emissions
• Scope 2 emissions
• Scope 3 emissions
• Energy consumption
• Renewable-energy usage
• Water
• Waste
• Pollution

Social Information

• Employee numbers
• Turnover
• Diversity
• Training
• Health and safety
• Labour practices
• Human-rights indicators

Governance Information

• Board information
• Ethics
• Anti-corruption
• Whistleblower mechanisms
• Governance processes
• Risk management

Strategic Information

• Sustainability targets
• Climate targets
• Transition plans
• Risk-management processes

The exact scope depends on the applicable reporting requirements and assurance engagement.

5. What Is the Difference Between Limited and Reasonable Assurance?

One of the most important concepts in ESG assurance is the level of assurance.

Limited Assurance

Limited assurance provides a lower level of assurance.

The practitioner performs procedures that are less extensive than those in a reasonable assurance engagement.

The conclusion is generally expressed in a negative form, such as:

“Nothing has come to our attention that causes us to believe…”

Reasonable Assurance

Reasonable assurance provides a higher level of assurance.

The practitioner performs more extensive procedures and obtains a higher level of confidence.

The conclusion is generally expressed positively.

A key point is:

Reasonable assurance does not mean absolute assurance.

No assurance engagement provides absolute certainty.

ICAI’s SSA 5000 is designed as a comprehensive framework for sustainability assurance, while the international ISSA 5000 framework covers both reasonable and limited assurance engagements.

6. Limited Assurance vs Reasonable Assurance

The precise procedures depend on the engagement’s circumstances, criteria and applicable professional standards.

7. Why Are Companies Moving Toward Assurance?

There are several reasons.

Regulatory Pressure

Regulators in different jurisdictions are increasingly incorporating assurance requirements into sustainability-reporting frameworks.

Investor Expectations

Investors increasingly want reliable sustainability information.

Greenwashing Concerns

Independent assurance can reduce the risk of unsupported claims.

Internal Management

The assurance process can identify weaknesses in data systems and controls.

Financing

Reliable ESG information can support discussions with lenders and investors.

Reputation

Assured information can increase stakeholder confidence.

8. Is ESG Assurance Mandatory Everywhere?

No.

There is no single global rule requiring every company to obtain ESG assurance.

The IFRS Foundation specifically states that the ISSB Standards themselves do not mandate assurance. Jurisdictions determine whether assurance is required and, if so, what level and scope apply.

Some jurisdictions have introduced or are introducing mandatory sustainability assurance, while others permit or encourage voluntary assurance.

Therefore, companies should always examine the requirements applicable to their jurisdiction, industry and reporting framework.

9. ESG Assurance in India

India is developing a more structured sustainability assurance ecosystem.

SEBI’s BRSR Core framework introduced a glide path for assurance/assessment of specified ESG indicators for covered listed entities.

At the professional level, ICAI has now issued SSA 5000 – General Requirements for Sustainability Assurance Engagements.

The standard is effective for sustainability assurance engagements relating to periods beginning on or after 1 April 2027.

ICAI has also issued a separate Framework for Sustainability Assurance Engagements, which sets out fundamental principles and concepts supporting consistent application of sustainability assurance principles.

This represents a significant development for the Indian accounting profession.

10. What Is SSA 5000?

SSA 5000 – General Requirements for Sustainability Assurance Engagements is ICAI’s sustainability assurance standard.

According to ICAI, it provides:

• A principles-based approach
• A framework-neutral approach
• Consistency in sustainability assurance
• Alignment with international sustainability assurance developments
• India-specific provisions where appropriate

It is aligned with the IAASB’s ISSA 5000 while incorporating provisions suited to the Indian regulatory and professional environment.

11. Why SSA 5000 Matters for Indian CAs

SSA 5000 is significant because it establishes a dedicated professional framework for sustainability assurance.

It creates opportunities for CAs in:

• BRSR assurance
• Sustainability assurance
• ESG data verification
• Climate disclosures
• Sustainability KPIs
• ESG controls
• Sustainability reporting advisory
• Assurance readiness

It also increases the importance of professional competence in sustainability-related matters.

12. ISSA 5000: The Global Context

At the international level, the International Auditing and Assurance Standards Board (IAASB) has developed ISSA 5000 – General Requirements for Sustainability Assurance Engagements.

It is designed as a comprehensive, profession-agnostic sustainability assurance standard.

It can be applied to sustainability assurance engagements involving both limited and reasonable assurance.

The international framework is intended to support greater consistency in sustainability assurance across jurisdictions.

13. What Does an ESG Assurance Practitioner Actually Do?

An assurance practitioner may perform procedures such as:

• Understanding the reporting framework
• Understanding the organisation
• Identifying relevant risks
• Assessing material information
• Evaluating internal controls
• Testing ESG data
• Examining supporting documentation
• Performing analytical procedures
• Testing calculations
• Reviewing assumptions
• Evaluating estimates
• Considering management representations
• Reaching an assurance conclusion

The procedures depend on the level of assurance and the engagement circumstances.

14. ESG Assurance Begins With Criteria

An assurance engagement requires appropriate criteria against which information is evaluated.

Possible criteria may include:

• BRSR requirements
• BRSR Core requirements
• IFRS S1
• IFRS S2
• ESRS
• GRI Standards
• GHG Protocol
• Applicable laws and regulations
• Organisation-specific sustainability criteria

The practitioner must understand exactly what the company is claiming compliance with.

15. Materiality in ESG Assurance

Materiality is fundamental.

The practitioner needs to understand which information could influence users’ decisions.

For example, if a company reports:

Scope 1 emissions = 50,000 tonnes CO₂e

the practitioner needs to understand:

• How was this calculated?
• What sources were included?
• What emission factors were used?
• What organisational boundary was applied?
• Were there exclusions?
• Are estimates involved?
• Is supporting evidence available?

Materiality helps determine the nature and extent of assurance procedures.

16. ESG Assurance and Risk Assessment

The practitioner should identify areas where material misstatement or misleading information could occur.

Possible risks include:

• Incorrect emission factors
• Missing facilities
• Duplicate data
• Incorrect unit conversion
• Unsupported estimates
• Incomplete employee data
• Incorrect Scope 3 calculations
• Inaccurate safety statistics
• Unsupported ESG claims

Higher-risk areas generally require greater professional attention.

17. ESG Data Testing

Suppose a company reports annual electricity consumption of:

10 million kWh

The practitioner may examine:

• Electricity invoices
• Meter readings
• ERP records
• Utility statements
• Plant records
• Calculation sheets
• Consolidation files

The practitioner may reconcile source information to the reported figure.

This is similar in principle to testing financial information, although ESG data has its own measurement challenges.

18. Testing GHG Emissions

GHG assurance can involve testing:

Activity Data × Emission Factor = Emissions

For example:

Electricity consumption
× Applicable emission factor
= Scope 2 emissions

The practitioner may test:

• Electricity data
• Emission factors
• Conversion formulas
• Organisational boundaries
• Consolidation
• Assumptions
• Exclusions

19. Scope 3 Assurance Challenges

Scope 3 can be more difficult because the data often comes from third parties.

Examples include:

• Purchased goods
• Transportation
• Business travel
• Employee commuting
• Use of sold products
• End-of-life treatment

Challenges include:

• Supplier data availability
• Estimates
• Secondary emission factors
• Data consistency
• Different methodologies

The assurance practitioner must understand the measurement methodology and related uncertainties.

20. ESG Assurance and Internal Controls

Strong internal controls make assurance more effective.

Important controls include:

Data Ownership

Every major ESG metric should have a responsible owner.

Review

Data should be reviewed before reporting.

Documentation

Methodologies and assumptions should be documented.

Reconciliation

ESG information should be reconciled with relevant operational or financial data where appropriate.

Approval

Final ESG information should have formal management approval.

21. ESG Data Governance

A mature company can establish:

Data Source → Data Owner → Calculation → Review → Approval → Disclosure

This creates an audit trail.

For example:

Plant electricity bill

→ Plant finance team

→ Energy calculation

→ Sustainability team

→ Finance review

→ Management approval

→ ESG report

Such controls improve reliability.

22. ESG Assurance and Greenwashing

Greenwashing occurs when sustainability claims are exaggerated or unsupported.

Assurance can help reduce the risk of misleading quantitative disclosures.

For example, if a company claims:

“We reduced our emissions by 40%.”

the assurance process may examine:

• Baseline year
• Reporting boundary
• Current-year emissions
• Methodology
• Acquisitions/divestments
• Offsets
• Calculation methodology

Assurance does not automatically make every sustainability claim truthful, but it can provide greater confidence over information within the assurance scope.

23. ESG Assurance and Management Responsibility

A fundamental principle is:

Management is responsible for the sustainability information.

The assurance practitioner provides an independent conclusion.

Management should:

• Establish systems
• Maintain records
• Select appropriate criteria
• Prepare disclosures
• Maintain internal controls
• Provide evidence

The assurance practitioner should remain independent and exercise professional judgement.

24. Independence in ESG Assurance

Independence is essential.

An assurance practitioner should avoid situations where advisory activities create unacceptable conflicts with assurance responsibilities.

ICAI’s revised 13th Edition of the Code of Ethics, effective from 1 April 2026, includes a dedicated volume covering ethics standards for sustainability assurance, including independence standards.

This reinforces the importance of ethical and independent sustainability assurance.

25. Competence Required for ESG Assurance

ESG assurance requires more than traditional accounting knowledge.

Professionals may need knowledge of:

Accounting

• Financial reporting
• Internal controls
• Audit principles

Sustainability

• ESG frameworks
• BRSR
• ISSB
• Climate disclosures

Environmental

• GHG accounting
• Energy
• Water
• Waste

Social

• Workforce
• Safety
• Human rights

Technology

• Data analytics
• ERP systems
• ESG platforms

Professional Skills

• Professional scepticism
• Evidence evaluation
• Risk assessment
• Documentation
• Judgement

26. Role of CA Professionals in ESG Assurance

CAs are well positioned to develop sustainability assurance practices because of their existing expertise in:

• Audit
• Assurance
• Internal controls
• Financial reporting
• Risk assessment
• Evidence
• Professional ethics

However, sustainability assurance requires additional technical competence.

A CA should not assume that financial-audit expertise alone is sufficient for every sustainability assurance engagement.

27. Role of CMA Professionals in ESG Assurance

CMAs can contribute significantly through their expertise in:

• Cost data
• Management accounting
• Performance measurement
• Resource efficiency
• Budgeting
• Operational data
• Cost-benefit analysis

CMAs can also support organisations in preparing ESG information that is ready for assurance.

For example:

Energy Cost → Energy Consumption → Emissions → ESG KPI → Assurance Evidence

28. ESG Assurance and Internal Audit

Internal audit and external assurance are different.

Internal Audit

Provides independent internal assessment to management and the Board.

External Assurance

Provides an independent assurance conclusion to intended users under the applicable engagement framework.

Internal audit can nevertheless strengthen ESG readiness by testing:

• Controls
• Data
• Governance
• Processes
• Compliance

29. ESG Assurance Readiness

Companies should not wait until the assurance engagement begins.

A good preparation process includes:

Step 1

Identify all reported ESG metrics.

Step 2

Document methodologies.

Step 3

Identify data owners.

Step 4

Create evidence files.

Step 5

Establish internal controls.

Step 6

Perform internal testing.

Step 7

Resolve data gaps.

Step 8

Maintain an audit trail.

Step 9

Conduct management review.

Step 10

Engage the assurance practitioner early where appropriate.

30. ESG Evidence File

For every important KPI, the company should ideally maintain an evidence file.

For example:

KPI

Scope 1 emissions

Evidence

• Fuel purchase records
• Fuel consumption records
• Meter data
• Emission factors
• Calculation workbook
• Methodology
• Review documentation

Approval

Responsible manager + management review

This creates a clear chain of evidence.

31. ESG Assurance and Technology

Technology can improve assurance efficiency.

Useful technologies include:

• ERP systems
• ESG reporting platforms
• Data analytics
• Automated reconciliations
• Digital evidence repositories
• Power BI dashboards
• AI-assisted anomaly detection

For example, data analytics may identify:

• Unusual energy consumption
• Duplicate records
• Missing months
• Unexpected emission changes
• Inconsistent supplier data

Technology can support professional judgement but should not replace it.

32. ESG Assurance and AI

Artificial intelligence can support:

• Document analysis
• Data classification
• Anomaly detection
• Trend analysis
• Risk identification
• Evidence organisation

However, AI-generated information should be validated.

The assurance practitioner remains responsible for professional judgement and the quality of procedures performed.

33. ESG Assurance and Supply Chain

Supply-chain ESG information creates additional assurance challenges.

A company may depend on hundreds of suppliers.

Questions include:

• Is supplier data reliable?
• Is the methodology consistent?
• Are estimates being used?
• Is supplier information independently verified?
• Are high-risk suppliers subject to additional procedures?

The company should establish a risk-based approach rather than assuming that all supplier data has equal reliability.

34. ESG Assurance and BRSR

For Indian listed companies subject to BRSR-related requirements, assurance or assessment of specified ESG information is becoming increasingly important.

Companies should therefore establish:

• BRSR data owners
• BRSR control matrices
• Evidence repositories
• Data validation procedures
• Management review
• Internal testing

The objective should be to make the BRSR reporting process assurance-ready rather than simply report-ready.

35. ESG Assurance and Investors

Investors may place greater confidence in information that has undergone appropriate independent assurance.

However, investors should still understand:

• What information was assured?
• What criteria were used?
• What level of assurance was provided?
• What period was covered?
• What limitations exist?
• Was the entire sustainability report assured or only selected indicators?

An assurance conclusion should therefore be read in context.

36. ESG Assurance Report

An assurance report may typically identify:

• Subject matter
• Applicable criteria
• Management’s responsibilities
• Practitioner’s responsibilities
• Level of assurance
• Scope
• Procedures or basis of conclusion
• Assurance conclusion
• Relevant limitations

The exact structure depends on the applicable standard and engagement.

37. What ESG Assurance Does Not Mean

Assurance does not necessarily mean:

• The company is sustainable.
• The company has no ESG risks.
• Every ESG statement has been independently verified.
• The company has zero emissions.
• The company’s strategy will succeed.
• Future targets will definitely be achieved.

Assurance provides confidence over the specified subject matter and criteria within the defined engagement scope.

38. Assurance vs Certification

These terms should not be confused.

Assurance

Provides an independent conclusion on information against specified criteria.

Certification

Generally involves assessing conformity with specified requirements or standards under a certification scheme.

Verification

May refer to checking specific information or claims.

The exact meaning depends on the applicable standard and engagement.

39. Common ESG Assurance Challenges

1. Poor Data Quality

Data may not have been designed for assurance.

2. Multiple Data Sources

Information may come from finance, HR, operations and suppliers.

3. Estimates

Some ESG metrics require estimation.

4. Methodology Changes

Changing calculation methods can affect comparability.

5. Scope 3

Value-chain data can be difficult to obtain.

6. Manual Processes

Spreadsheets can create control weaknesses.

7. Lack of Documentation

Companies may have data but not sufficient evidence.

8. Limited Expertise

Sustainability data requires specialised knowledge.

40. How Companies Can Become Assurance-Ready

A practical assurance-readiness checklist is:

☐ Define reporting boundaries
☐ Identify applicable criteria
☐ Identify material ESG metrics
☐ Assign data owners
☐ Document methodologies
☐ Establish internal controls
☐ Maintain supporting evidence
☐ Reconcile relevant data
☐ Review calculations
☐ Test data internally
☐ Document estimates
☐ Track methodology changes
☐ Establish management approval
☐ Maintain an ESG audit trail

41. ESG Assurance Maturity Model

Level 1 – Basic

Data is collected manually with limited documentation.

Level 2 – Controlled

Data owners and review processes exist.

Level 3 – Assurance Ready

Evidence, controls and methodologies are documented.

Level 4 – Assured

Selected ESG information undergoes external assurance.

Level 5 – Integrated

ESG data is integrated with financial reporting, enterprise risk management and management information systems.

Companies should aim to progressively move toward integrated sustainability reporting and assurance.

42. ESG Assurance for MSMEs

Not every MSME will immediately require formal external assurance.

However, MSMEs can become assurance-ready by maintaining:

• Energy records
• Electricity bills
• Fuel records
• Employee records
• Safety records
• Waste records
• Supplier information
• ESG policies
• Governance documentation

This can make it easier to respond to customer or lender ESG requests.

43. ESG Assurance and Sustainable Finance

As sustainability-linked financing grows, reliable ESG KPIs become increasingly important.

Suppose a loan includes a target:

Reduce emissions intensity by 20%.

The company needs:

• A baseline
• Defined methodology
• Reliable data
• Measurement
• Evidence
• Appropriate verification or assurance

Otherwise, the sustainability-linked feature may become difficult to evaluate.

44. ESG Assurance and Green Bonds

Green financing may involve reporting on the use of proceeds and environmental impact.

Relevant information may include:

• Project allocation
• Renewable-energy capacity
• Energy savings
• Emission reductions
• Eligible expenditures

Independent assurance or verification may be relevant depending on the financing framework and transaction requirements.

45. ESG Assurance and Climate Targets

Companies increasingly publish targets such as:

• Net zero by 2050
• 50% emission reduction by 2030
• 100% renewable electricity
• Zero waste to landfill

Assurance over historical information is different from guaranteeing that future targets will be achieved.

Future-oriented information requires careful consideration of:

• Assumptions
• Methodologies
• Plans
• Dependencies
• Uncertainties

An assurance engagement should clearly define what is within scope.

46. Role of the CFO in ESG Assurance

The CFO should help establish:

• ESG data governance
• Internal controls
• Reporting calendars
• Financial/ESG reconciliations
• Management review
• Evidence retention
• Assurance coordination

The CFO can help ensure that ESG reporting receives the same discipline increasingly expected of financial reporting.

47. Role of the Board

The Board should understand:

• What ESG information is reported
• Which information is assured
• What level of assurance applies
• Major data limitations
• Material ESG risks
• Major assurance findings
• Management’s corrective actions

Board oversight helps establish accountability.

48. Role of CA and CMA in Building Assurance-Ready Systems

A CA or CMA can help an organisation move from:

Unstructured ESG Data

to:

Controlled ESG Data

to:

Assurance-Ready ESG Data

The process involves:

Measure → Document → Control → Review → Reconcile → Assure

This is an important emerging professional opportunity.

49. 90-Day ESG Assurance-Readiness Plan

Days 1–30: Diagnostic

• Identify ESG disclosures
• Identify applicable criteria
• Map data sources
• Identify gaps
• Assign owners

Days 31–60: Controls

• Create control matrix
• Document methodologies
• Establish evidence files
• Improve data validation
• Conduct reconciliations

Days 61–90: Testing

• Perform internal testing
• Correct errors
• Review assumptions
• Conduct mock assurance
• Finalise reporting processes

This approach can significantly reduce last-minute reporting pressure.

50. The Future of ESG Assurance

The direction of sustainability reporting is increasingly toward:

More Data → More Regulation → More Transparency → More Assurance

Global developments such as ISSA 5000 and national frameworks such as India’s SSA 5000 are contributing to a more structured sustainability assurance ecosystem.

At the same time, the IFRS Foundation expects jurisdictions adopting ISSB-based reporting to make their own decisions regarding assurance requirements, scope and timing.

For professionals, this means sustainability assurance is likely to become an important specialist field rather than a temporary reporting trend.

51. Key Takeaways for Companies

Companies should remember five principles:

1. Reporting Is Not Enough

Information should be reliable.

2. Assurance Starts With Good Data

Poor data cannot become reliable merely because an assurance engagement is performed.

3. Controls Matter

ESG data requires governance and internal controls.

4. Scope Matters

Understand exactly which information is covered by assurance.

5. Independence Matters

Assurance must be performed under appropriate professional and ethical requirements.

52. Key Takeaways for CA and CMA Professionals

ESG assurance creates opportunities across:

ESG Reporting

BRSR

Data Controls

Carbon Accounting

Internal Audit

Sustainability Assurance

ESG Due Diligence

Risk Management

Sustainable Finance

Management Advisory

For CAs, assurance, audit, controls and professional ethics provide a strong foundation.

For CMAs, costing, performance measurement, operational data and resource efficiency provide valuable complementary skills.

Conclusion

ESG assurance is becoming an essential component of a credible sustainability reporting ecosystem.

As companies publish increasingly detailed information about climate, emissions, workforce, governance and sustainability performance, stakeholders need confidence that the information is supported by appropriate evidence and prepared using suitable criteria.

The evolution can be summarised as:

ESG Reporting → ESG Controls → ESG Assurance → ESG Confidence

India’s issuance of SSA 5000 in 2026 marks an important milestone for the country’s sustainability assurance profession. The standard is effective for sustainability assurance engagements relating to periods beginning on or after 1 April 2027.

For businesses, the message is clear:

Do not wait for assurance to discover weaknesses in your ESG data. Build assurance-ready systems from the beginning.

For finance professionals, the opportunity is equally clear:

ESG assurance is becoming a new intersection of accounting, sustainability, data, risk, technology and professional judgement.

The future professional will not merely ask:

“What has the company reported?”

The professional will also ask:

“Can we demonstrate that the information is reliable, controlled, supported by evidence and fit for decision-making?”

That is the growing importance of ESG assurance.