ESG Reporting Frameworks: A Practical Comparison Guide

GRI, ISSB, CSRD, TCFD, CDP, SASB — the list of ESG reporting frameworks grows every year, and each one claims to be the definitive standard. For a sustainability or finance professional trying to work out which applies to their company, the landscape is genuinely confusing. This guide cuts through it: what each framework requires, which ones are mandatory, and how to decide what your company needs to report.

Mandatory vs. Voluntary: The Critical Distinction

The first thing to understand is that most ESG frameworks are voluntary. Companies choose to report against them because investors, customers, or insurers expect it. A smaller number are mandatory — set by law or regulation — and failing to comply has legal consequences.

• Mandatory: CSRD (EU), SEC Climate Disclosure (US), California SB 253 and SB 261, UK Sustainability Disclosure Requirements (UK SRS), HKEX ESG Reporting (Hong Kong listed companies)
• Voluntary but widely adopted: GRI, CDP, TCFD (being superseded by ISSB), UN SDGs
• Referenced by mandatory frameworks: ISSB (IFRS S1/S2) is voluntary in most jurisdictions but is incorporated into mandatory requirements in an increasing number of countries; ESRS references both GRI and ISSB

A company might be subject to one mandatory framework, multiple frameworks, or none — depending on where it is incorporated, where it lists shares, where it sells, and how large it is.

The Major Frameworks Explained

GRI (Global Reporting Initiative)

GRI is the most widely used voluntary framework globally, with over 10,000 organisations reporting against it. It covers economic, environmental, and social impacts using a modular structure: universal standards that apply to all reporters, sector standards for specific industries, and topic standards for individual disclosures. GRI uses an impact materiality approach — report on what your company does to the world, not what the world does to your company.

ISSB (IFRS S1 and S2)

The International Sustainability Standards Board published IFRS S1 (general sustainability disclosures) and IFRS S2 (climate-related disclosures) in June 2023. ISSB uses financial materiality — report on sustainability issues that affect enterprise value. IFRS S2 is heavily influenced by TCFD and requires Scope 1, 2, and 3 emissions disclosure. Adoption is voluntary at the international level but is being mandated in Australia, Singapore, the UK, and several other jurisdictions.

CSRD and ESRS (EU)

The Corporate Sustainability Reporting Directive requires EU companies and large non-EU companies with significant EU operations to report against European Sustainability Reporting Standards. ESRS uses double materiality — both impact and financial perspectives are required. CSRD is the most comprehensive mandatory framework currently in force: it covers all ESG topics, requires external assurance, and has a phased rollout from 2024 through 2028 depending on company size.

TCFD (Task Force on Climate-related Financial Disclosures)

TCFD was the dominant voluntary climate disclosure framework from its launch in 2017 until ISSB published S2 in 2023. The FSB formally disbanded TCFD in 2024, transferring monitoring to ISSB. Companies that built TCFD-aligned disclosures will find most of the structure carries over to ISSB S2 — the four pillars (governance, strategy, risk management, metrics and targets) remain, with some additions.

CDP

CDP runs the largest global environmental disclosure system, with questionnaires on climate, water, and forests. CDP is voluntary but is increasingly required by investors and customers as part of procurement and supply chain due diligence. Scores (A through D-) are publicly available. CDP questionnaires align substantially with TCFD and increasingly with ISSB S2.

Which Framework Applies to Your Company

Work through these questions in order:

1. Are you an EU company or do you have substantial EU operations? If yes, CSRD applies if you meet the size thresholds (large companies from 2024; SMEs listed on EU markets from 2026).
2. Are you a US public company? SEC climate disclosure rules require Scope 1 and 2 reporting for large accelerated filers from 2026 (litigation has paused implementation — monitor developments).
3. Do you operate or report in California? SB 253 (Scope 1/2/3 emissions) and SB 261 (climate risk) apply to companies with over $1B and $500M revenue respectively doing business in California.
4. Are your investors or customers requesting a specific framework? GRI and CDP are the most common investor and customer-driven requests for non-mandatory reporters.
5. Do you want to prepare for likely future mandates? Aligning with ISSB S1/S2 now is the most efficient preparation path given its adoption trajectory.

Many companies end up reporting against multiple frameworks because their mandatory obligations (CSRD) and voluntary commitments (CDP, GRI) overlap. The good news: the data requirements converge significantly. ESRS explicitly references GRI, and ISSB S2 is built on TCFD foundations. A single robust data collection process can serve most frameworks simultaneously.

Where the Frameworks Overlap

The data convergence across frameworks is more significant than the differences. Scope 1, 2, and 3 GHG emissions are required by CSRD (ESRS E1), ISSB S2, CDP Climate, SEC rules, and SB 253. Energy consumption data underlies most of these. Governance structure, board oversight of sustainability, and risk management processes appear across CSRD, ISSB S1, and TCFD.

Investing in a single, well-structured data collection process — rather than separate processes for each framework — is the practical implication of this convergence. The frameworks differ on what they emphasise and how they define materiality; they don't require fundamentally different data.

Choosing a Platform to Span Multiple Frameworks

For companies subject to multiple frameworks, the operational priority is a data platform that maps collected data to each framework's requirements without duplication. The alternative — maintaining separate spreadsheets or tools for each — creates version-control problems, inconsistencies across disclosures, and significant manual overhead at reporting time.

Brightest's sustainability reporting standards overview covers how specific standards fit within this broader framework landscape. For companies beginning their CSRD journey, CSRD reporting software that connects materiality assessment, data collection, and disclosure in a single workflow is the most efficient path to compliance.