ESG Reporting: A Practical Guide for Companies

Executive Overview

ESG reporting has moved from voluntary best practice to regulatory mandate. The EU Corporate Sustainability Reporting Directive (CSRD) now requires approximately 50,000 companies to disclose detailed sustainability information. In parallel, the International Sustainability Standards Board (ISSB) has published IFRS S1 and S2, creating a global baseline for capital-market-focused disclosures.

For most organisations, the challenge is not willingness — it is knowing where to start, which standards apply, and how to build a reporting process that satisfies auditors, regulators, and investors without draining resources.

This guide explains the regulatory landscape, the standards that matter, and the practical workflow for building a compliant ESG report.

What Is ESG Reporting?

ESG reporting is the structured disclosure of environmental, social, and governance data by companies to investors, regulators, and other stakeholders. It covers:

• Environmental: Greenhouse gas emissions, energy use, water consumption, waste management, biodiversity impact, and climate risk exposure.
• Social: Workforce diversity, health and safety, human rights in supply chains, community relations, and customer data protection.
• Governance: Board composition and independence, executive compensation, anti-corruption policies, lobbying activities, and whistleblower protections.

Unlike traditional financial reporting, ESG disclosures often include forward-looking metrics, qualitative narratives, and third-party assurance. The goal is to give stakeholders a complete picture of how a company creates or erodes long-term value — including value that does not appear on a balance sheet.

Why ESG Reporting Matters

Three forces are driving the shift toward mandatory, detailed ESG disclosure:

• Regulatory pressure: CSRD in the EU, SEC climate disclosure rules in the United States, and similar requirements in the UK, Australia, and Japan mean companies face legal obligations — not just expectations.
• Capital access: Institutional investors increasingly screen portfolios using ESG data. Poor disclosure can limit access to green bonds, sustainability-linked loans, and certain investor mandates.
• Operational risk: Climate transition risks, supply chain human rights violations, and governance failures can destroy value rapidly. Reporting forces internal visibility before external exposure.

For sustainability directors and CFOs, the business case is straightforward: compliance is becoming compulsory, and early movers gain competitive advantage through better data, stronger stakeholder trust, and lower cost of capital.

CSRD: The EU Corporate Sustainability Reporting Directive

The CSRD replaces the Non-Financial Reporting Directive (NFRD) and dramatically expands the scope and depth of sustainability reporting in the European Union.

Who Must Report

• Large EU undertakings meeting two of three criteria: >250 employees, >€50 million turnover, or >€25 million balance sheet total.
• Listed SMEs, with simplified standards and a delayed timeline.
• Non-EU companies with significant EU operations: net turnover >€150 million in the EU, plus a large branch or subsidiary.

Key Requirements

• Double materiality assessment (see below).
• Disclosure aligned with the European Sustainability Reporting Standards (ESRS).
• Digital tagging using the European Single Electronic Format (ESEF).
• Limited assurance by statutory auditors, with reasonable assurance phased in later.

The first wave of companies began reporting in 2025 for fiscal year 2024. Non-EU companies enter the scope in 2028 for fiscal year 2027. Read the CSRD Guide →

ESRS: European Sustainability Reporting Standards

ESRS are the technical standards that define what companies must disclose under CSRD. They are developed by EFRAG and endorsed by the European Commission.

The standards are organised into cross-cutting standards (ESRS 1 and 2) and topical standards covering environment, social, and governance themes:

• ESRS 1 (General Requirements): Double materiality, value chain, time horizons, and structure of disclosures.
• ESRS 2 (General Disclosures): Governance, strategy, impact-risk-opportunity management, and metrics and targets.
• Topical standards: Climate change (E1), pollution (E2), water and marine resources (E3), biodiversity (E4), resource use and circular economy (E5), own workforce (S1), workers in the value chain (S2), affected communities (S3), consumers and end-users (S4), and business conduct (G1).

Companies apply the "comply or explain" principle for topical standards: they report on a topic if it is material, and explain why if it is not.

Double Materiality Explained

Double materiality is the defining feature of CSRD and ESRS. It requires companies to assess sustainability matters from two perspectives:

• Financial materiality (outside-in): How do sustainability risks and opportunities affect the company's financial position, performance, and cash flows? This aligns with the ISSB's approach.
• Impact materiality (inside-out): How do the company's activities affect people and the environment? This includes effects across the entire value chain, not just direct operations.

A topic is material if it is significant from either perspective. If either financial or impact materiality is met, the company must disclose. This means CSRD reporters often disclose more than ISSB-only reporters.

The assessment must be documented, involve stakeholders, and be reviewed periodically. It is not a one-time checkbox — it is the foundation of the entire reporting process.

ISSB and IFRS Sustainability Disclosure Standards

The International Sustainability Standards Board (ISSB), part of the IFRS Foundation, publishes standards designed for global capital markets. Its first two standards are:

• IFRS S1 (General Requirements for Sustainability-related Disclosures): Sets out core requirements for disclosing sustainability-related risks and opportunities useful to investors.
• IFRS S2 (Climate-related Disclosures): Requires disclosure of climate-related risks and opportunities, including Scope 1, 2, and 3 greenhouse gas emissions, climate targets, and transition plans.

Unlike CSRD, ISSB standards focus exclusively on financial materiality — what investors need to know. This creates an important distinction: ISSB-aligned reports answer "how does sustainability affect our financial value?" while CSRD-aligned reports answer that question and "how do we affect people and the planet?"

Many multinational companies will need to report under both frameworks. The good news: the ISSB and EFRAG have worked to align standards where possible, reducing duplication.

Typical ESG Reporting Workflow

A robust ESG reporting process typically follows these stages:

1. Governance setup: Assign board-level oversight, establish a cross-functional working group (sustainability, finance, legal, HR, operations), and define the reporting boundary.
2. Double materiality assessment: Identify sustainability topics, assess financial and impact materiality, engage stakeholders, and document conclusions.
3. Gap analysis: Map existing data against ESRS or ISSB requirements. Identify missing metrics, data collection processes, and system integrations.
4. Data collection: Build or enhance data pipelines for emissions, workforce metrics, supply chain data, and governance information. Implement controls to ensure accuracy.
5. Draft disclosures: Prepare narrative disclosures, quantitative metrics, and forward-looking targets. Ensure consistency with financial reporting and strategic planning.
6. Internal review: Validate data, check for completeness, and align disclosures with the company's risk management and strategy narratives.
7. Assurance: Engage statutory auditors or independent assurance providers for limited assurance (CSRD requirement), with reasonable assurance phased in later.
8. Publication: Publish in the required digital format (ESEF for CSRD), file with the relevant authority, and communicate to stakeholders.

Most companies need 12–18 months for the first full reporting cycle. Starting early is not optional if the deadline is fixed.

Common Implementation Challenges

Companies consistently encounter the same obstacles when building ESG reporting capabilities:

• Data fragmentation: ESG data lives in HR systems, ERP platforms, sustainability spreadsheets, and supplier questionnaires. Consolidating it into auditable metrics is technically and organisationally demanding.
• Scope 3 emissions: Calculating emissions across the value chain requires supplier engagement, emission factor selection, and methodological choices that are hard to standardise.
• Double materiality judgment: There is no universal threshold for materiality. Companies must develop defensible methodologies, document stakeholder input, and accept that conclusions may be challenged.
• Resource constraints: ESG reporting is often added to existing sustainability or finance teams without additional headcount or budget.
• Evolving standards: ESRS and ISSB standards are new. Guidance continues to emerge, and companies must stay current while maintaining reporting consistency year over year.

How Terrnix Helps

Terrnix provides practical tools and guidance to reduce the complexity of ESG reporting:

• Carbon accounting: Our carbon footprint calculator and carbon accounting hub help you calculate Scope 1, 2, and 3 emissions with transparent methodology.
• Readiness assessment: Our Carbon Accounting Readiness Assessment identifies your biggest reporting gaps in 25 questions.
• CSRD guidance: Our CSRD Guide breaks down the directive into actionable steps, timelines, and requirements.
• Knowledge resources: Our sustainability glossary and FAQ clarify terminology and common questions.
• Assessment tools: Our carbon calculator and other tools support quantitative disclosures required by ESRS.

We do not offer audit services or legal advice. We build tools that help you collect better data, understand requirements, and communicate clearly.