ISSB standards (IFRS S1 and S2): global sustainability reporting implementation guide

By mid-2025, more than 30 jurisdictions representing over 60% of global GDP had committed to adopting or aligning with the International Sustainability Standards Board (ISSB) standards IFRS S1 and S2 (IFRS Foundation, 2025). Since becoming effective on January 1, 2024, these two standards have reshaped the baseline for sustainability disclosure worldwide, with early adopter countries like Australia, Canada, Japan, Nigeria, and the United Kingdom embedding ISSB requirements into domestic law or regulatory guidance. An estimated 50,000+ reporting entities globally will be required to comply with ISSB-aligned frameworks by 2027, creating an urgent need for structured implementation strategies (IOSCO, 2024). This guide provides a comprehensive, step-by-step approach to understanding, planning for, and executing IFRS S1 and S2 compliance.

Why It Matters

IFRS S1 (General Requirements for Disclosure of Sustainability-related Financial Information) and IFRS S2 (Climate-related Disclosures) represent the first truly global baseline for sustainability reporting. Before the ISSB published these standards in June 2023, companies navigated a fragmented patchwork of voluntary frameworks including TCFD, SASB, GRI, and CDP, each with different scopes, metrics, and reporting boundaries. The ISSB consolidated these into a single, investor-focused architecture designed for interoperability with financial statements prepared under IFRS Accounting Standards.

The capital markets rationale is substantial. A 2024 PwC survey found that 75% of institutional investors considered sustainability disclosures "important" or "essential" in investment decisions, yet 94% believed corporate sustainability reporting contained at least some greenwashing (PwC, 2024). IFRS S1 and S2 address this trust gap by mandating decision-useful, comparable, and verifiable disclosures connected to enterprise value.

For companies, the cost of non-compliance extends beyond regulatory penalties. Organizations that fail to produce high quality sustainability disclosures face higher costs of capital, reduced access to green bond markets, and exclusion from institutional portfolios. Conversely, a 2025 study by the IFRS Foundation found that early ISSB adopters experienced a 12-18 basis point reduction in credit spreads relative to non-disclosing peers within the same sector (IFRS Foundation, 2025).

Key Concepts

IFRS S1: General Requirements

IFRS S1 establishes the overarching architecture for all sustainability-related financial disclosures. It requires companies to disclose information about sustainability-related risks and opportunities that could reasonably be expected to affect the entity's cash flows, access to finance, or cost of capital over the short, medium, and long term.

The standard is organized around four core pillars inherited from the TCFD framework:

• Governance: Board and management oversight of sustainability-related risks and opportunities.
• Strategy: Actual and potential effects of sustainability-related risks and opportunities on the entity's business model, value chain, and financial position.
• Risk management: Processes used to identify, assess, prioritize, and monitor sustainability-related risks and opportunities.
• Metrics and targets: Quantitative and qualitative measures used to monitor performance against stated goals.

IFRS S1 also requires companies to apply SASB Standards (now integrated into the ISSB) as guidance for identifying industry-specific disclosure topics and metrics across 77 sub-industries.

IFRS S2: Climate-related Disclosures

IFRS S2 builds on the S1 framework to prescribe specific climate-related disclosures. Key requirements include:

• Scope 1 and Scope 2 GHG emissions: Mandatory absolute reporting using the GHG Protocol methodology, measured in metric tons of CO2 equivalent.
• Scope 3 GHG emissions: Required disclosure of material Scope 3 categories, with a transition relief period allowing companies to defer Scope 3 reporting for the first annual reporting period.
• Climate scenario analysis: Entities must use scenario analysis to assess resilience of strategy under different climate pathways, including a scenario consistent with 1.5°C warming.
• Transition plans: Companies must disclose climate-related targets, including net-zero commitments, interim milestones, and progress against those targets.
• Industry-based metrics: S2 incorporates 68 industry-specific climate metrics derived from SASB Standards.

KPI	Description	Measurement
Scope 1 emissions	Direct GHG emissions from owned or controlled sources	tCO2e, absolute and intensity
Scope 2 emissions	Indirect emissions from purchased energy	tCO2e, location-based and market-based
Scope 3 emissions	Value chain emissions across 15 categories	tCO2e by material category
Climate transition plan progress	Achievement against stated decarbonization targets	% of interim target achieved
Internal carbon price	Shadow price applied to investment decisions	USD/tCO2e
Climate-related capital expenditure	Spending aligned with transition or adaptation	USD and % of total capex
Physical risk exposure	Assets or revenues exposed to acute/chronic climate hazards	% of assets, revenue at risk

Regulatory Timeline

The ISSB standards were published on June 26, 2023, and became effective for annual reporting periods beginning on or after January 1, 2024. However, adoption is jurisdiction-specific because the ISSB sets global standards while individual countries and regulators decide when and how to incorporate them into local law.

2024: Australia's Treasury released exposure drafts mandating ISSB-aligned climate reporting for the largest entities (Group 1: annual revenue > AUD 500 million) beginning January 2025. Canada's Canadian Securities Administrators (CSA) proposed National Instrument 51-107 aligned with ISSB. Nigeria became one of the first countries to mandate ISSB adoption through its Financial Reporting Council.

2025: The United Kingdom's Financial Conduct Authority (FCA) confirmed UK Sustainability Reporting Standards (UK SRS) modeled on ISSB for listed companies and large private firms, with first reports due for fiscal years beginning January 2025. Japan's Financial Services Agency integrated ISSB-aligned requirements into its Securities and Exchange Law amendments. Hong Kong, Singapore, and Malaysia finalized mandatory ISSB-aligned frameworks for listed companies.

2026: The EU's CSRD framework, while distinct from ISSB in scope, achieves interoperability through EFRAG-ISSB collaboration, with cross-mapping guidance published in Q1 2026. Australia's Group 2 entities (revenue > AUD 200 million) begin reporting. Brazil's CVM mandates ISSB adoption for all publicly traded companies.

2027 and beyond: Expanded coverage in Australia (Group 3: revenue > AUD 50 million), continued rollout across ASEAN, Latin America, and Africa. IOSCO has endorsed the standards for cross-border use, encouraging securities regulators globally to consider adoption (IOSCO, 2024).

Who Must Comply

IFRS S1 and S2 apply wherever jurisdictions choose to adopt them, typically targeting:

• Publicly listed companies in jurisdictions that have incorporated ISSB into listing rules or securities regulation.
• Large private companies meeting defined revenue, asset, or employee thresholds (varies by jurisdiction; for example, UK SRS applies to entities with > 750 employees and > £750 million turnover).
• Financial institutions including banks, insurers, and asset managers, which face accelerated timelines in several markets due to their systemic role.
• State-owned enterprises in jurisdictions like South Africa and Nigeria where government reporting frameworks reference ISSB.
• Multinational subsidiaries that may need to prepare ISSB-aligned data to support parent company consolidated reporting, even if the subsidiary's home jurisdiction has not yet adopted the standards.

Companies reporting under the EU's CSRD should note that while ESRS (European Sustainability Reporting Standards) differ from ISSB in their double materiality approach, the EFRAG-ISSB interoperability mapping allows CSRD-compliant data to substantially fulfill ISSB requirements as well.

Compliance Requirements

Materiality Assessment

IFRS S1 uses a financial materiality lens: information is material if omitting, misstating, or obscuring it could reasonably be expected to influence investor decisions. This differs from the "double materiality" standard used in the EU's ESRS, which also considers impact materiality. Companies must document their materiality assessment process, including how sustainability-related risks and opportunities were identified, evaluated, and prioritized.

Connected Disclosures

A distinguishing feature of ISSB is the requirement for "connected information," meaning sustainability disclosures must be linked to, and consistent with, the entity's financial statements. If a company identifies a climate-related risk in its IFRS S2 disclosure, the financial implications (such as asset impairments, provisions, or changes in useful life) must be reflected or cross-referenced in the financial statements.

Reporting Boundaries and Value Chain

Disclosures must cover the same reporting entity as the financial statements but extend to the entity's value chain where sustainability-related risks and opportunities arise. This requires companies to gather data from suppliers, distributors, customers, and end-of-life processors in a systematic and verifiable manner.

Assurance

While ISSB itself does not mandate assurance, the International Auditing and Assurance Standards Board (IAASB) published the International Standard on Sustainability Assurance (ISSA) 5000 in December 2024, providing a global framework for limited and reasonable assurance of sustainability disclosures. Several jurisdictions, including Australia and the UK, require limited assurance from the outset, progressing to reasonable assurance within three to five years.

Step-by-Step Implementation

Phase 1: Gap analysis (months 1 to 3). Map existing sustainability disclosures against IFRS S1 and S2 requirements. Identify data gaps, particularly in Scope 3 emissions, scenario analysis capabilities, and governance documentation. Benchmark against SASB industry-specific metrics for your sub-industry.

Phase 2: Governance design (months 2 to 4). Establish or formalize board-level oversight of sustainability risks. Define management roles and responsibilities. Create reporting lines between sustainability teams, finance, risk management, and internal audit.

Phase 3: Data infrastructure (months 3 to 8). Build or upgrade systems to capture, validate, and aggregate sustainability data at the same rigor as financial data. Prioritize Scope 1 and Scope 2 emissions measurement. Engage key suppliers on Scope 3 data collection. Implement internal controls over sustainability data.

Phase 4: Scenario analysis (months 4 to 9). Conduct climate scenario analysis using at least two scenarios, including one aligned with 1.5°C. Quantify financial impacts on strategy, business model, and asset valuations. Document assumptions, time horizons, and limitations.

Phase 5: Draft and review (months 8 to 11). Prepare draft IFRS S1 and S2 disclosures. Ensure connected information links sustainability and financial reporting. Subject disclosures to internal audit review and, where required, external limited assurance.

Phase 6: Publication and iteration (month 12). Publish disclosures alongside or within the annual report. Establish feedback mechanisms to improve data quality and scope for subsequent reporting cycles.

Common Pitfalls

Treating ISSB as a standalone compliance exercise. Organizations that isolate sustainability reporting from financial reporting processes fail to achieve the "connected information" requirement. Successful implementation integrates sustainability data into the same governance, controls, and assurance framework as financial statements.

Underestimating Scope 3 data complexity. Scope 3 emissions often represent 70 to 90% of a company's total carbon footprint, yet most organizations lack reliable upstream and downstream data. Starting with spend-based estimates and progressively upgrading to activity-based calculations avoids paralysis while maintaining credibility.

Ignoring industry-specific metrics. IFRS S2 references 68 climate metrics across SASB sub-industries. Companies that report only generic emissions data without addressing sector-specific metrics (such as methane intensity for oil and gas, or fleet fuel efficiency for transportation) fall short of investor expectations.

Delaying governance formalization. Both S1 and S2 require detailed disclosures on governance structures, including board competencies, oversight frequency, and integration into remuneration. Retroactively documenting these elements is difficult; building governance infrastructure early is essential.

Neglecting assurance readiness. Even where assurance is not immediately required, preparing data systems for eventual reasonable assurance avoids costly remediation. The IAASB's ISSA 5000 standard signals that assurance expectations will tighten globally.

Key Players

Standard-Setters and Regulators

• IFRS Foundation / ISSB - The standard-setting body responsible for IFRS S1 and S2, headquartered in Frankfurt with offices in Montreal and other cities.
• IOSCO (International Organization of Securities Commissions) - Endorsed ISSB standards in July 2023, encouraging member regulators across 130+ jurisdictions to adopt.
• EFRAG (European Financial Reporting Advisory Group) - Developed interoperability guidance mapping ESRS to ISSB requirements.
• IAASB (International Auditing and Assurance Standards Board) - Published ISSA 5000 for sustainability assurance in December 2024.

Advisory and Implementation Firms

• Deloitte - Global sustainability reporting advisory practice with ISSB implementation accelerators.
• PwC - Sustainability assurance and ISSB readiness services across 150+ countries.
• KPMG - Climate scenario analysis and ISSB gap assessment services.
• EY - Integrated sustainability and financial reporting advisory.

Technology and Data Providers

• Persefoni - Carbon accounting platform used by 200+ enterprises for ISSB-aligned emissions measurement.
• Workiva - ESG and financial reporting platform enabling connected ISSB and IFRS disclosures.
• S&P Global Sustainable1 - Data analytics platform providing ISSB-aligned climate risk metrics.

Real-World Examples

Unilever: Early Voluntary ISSB Alignment

Unilever became one of the first multinational consumer goods companies to voluntarily align its 2024 annual report with IFRS S1 and S2, covering over 400 brands across 190 countries. The company disclosed Scope 1, 2, and 3 emissions totaling approximately 55 million tCO2e, with Scope 3 representing 96% of the total footprint. Unilever's climate scenario analysis covered both 1.5°C and 3°C pathways, quantifying potential revenue impacts from physical risks to agricultural supply chains (estimated at EUR 300 to 500 million annually by 2040) and transition risks from carbon pricing in 12 key markets. The company credited the ISSB framework with streamlining its previously fragmented reporting across TCFD, CDP, and GRI, reducing external reporting preparation time by approximately 30%.

BHP Group: Mining Sector Compliance Under Australian Mandate

BHP Group, the world's largest mining company by market capitalization, began mandatory ISSB-aligned reporting under Australia's Group 1 requirements for its fiscal year starting July 2024. BHP disclosed Scope 1 emissions of 11.5 million tCO2e and Scope 2 emissions of 5.3 million tCO2e, with detailed breakdowns by operational asset. The company's transition plan included a USD 4.9 billion capital allocation toward decarbonization through 2030, covering operational electrification, renewable power purchase agreements, and carbon capture trials. BHP reported that implementing the ISSB-connected disclosure requirement revealed a previously undisclosed AUD 1.2 billion gap between its stated climate risk provisions and the financial statement carrying values of certain long-lived assets, prompting an impairment review of two coal-adjacent operations.

Mitsubishi UFJ Financial Group (MUFG): Financial Sector Adoption in Japan

MUFG, Japan's largest bank with over JPY 400 trillion in total assets, adopted ISSB-aligned climate disclosures for its fiscal year ending March 2025 under Japan's revised Securities and Exchange Law requirements. The bank disclosed financed emissions across its lending and investment portfolios totaling an estimated 180 million tCO2e, covering power generation, oil and gas, steel, and real estate sectors. MUFG's scenario analysis evaluated credit risk impacts under 1.5°C and 4°C pathways, identifying JPY 350 billion in potential credit losses from high-carbon sectors by 2050 under an accelerated transition scenario. The disclosure enabled MUFG to announce a revised sectoral decarbonization target, committing to a 31% reduction in financed emissions intensity for its power generation portfolio by 2030 (from a 2019 baseline), supported by JPY 50 trillion in sustainable finance commitments through 2030.

Action Checklist

• Determine which jurisdiction-specific ISSB adoption timeline applies to your entity and identify the first mandatory reporting period
• Conduct a gap analysis comparing current sustainability disclosures against IFRS S1 and S2 requirements, including SASB industry-specific metrics
• Establish or formalize board-level governance over sustainability-related risks and opportunities, documenting oversight processes and competencies
• Build data infrastructure for Scope 1, 2, and 3 emissions measurement using GHG Protocol methodology, prioritizing material Scope 3 categories
• Develop climate scenario analysis capabilities covering at least a 1.5°C pathway and quantifying financial impacts on strategy and asset valuations
• Prepare connected disclosures linking sustainability risks and opportunities to financial statement line items
• Engage external assurance providers to assess readiness for limited assurance, progressing toward reasonable assurance as required by your jurisdiction
• Map ISSB disclosures against CSRD/ESRS requirements (if operating in the EU) to eliminate duplicative reporting effort
• Train finance, risk management, and sustainability teams on ISSB requirements and integrated reporting workflows

FAQ

Q: How do IFRS S1 and S2 differ from TCFD? A: IFRS S2 incorporates all TCFD recommendations but goes further by mandating specific metrics (including Scope 1, 2, and 3 emissions), requiring industry-specific disclosures via SASB metrics, and demanding connected information with financial statements. TCFD was a voluntary framework; ISSB standards become mandatory where jurisdictions adopt them.

Q: Is Scope 3 reporting mandatory from day one? A: IFRS S2 includes a transition relief allowing entities to omit Scope 3 GHG emissions in their first annual reporting period. After that initial period, Scope 3 reporting is required for all material categories. Companies should use the transition period to build data collection systems and supplier engagement processes.

Q: How does ISSB relate to the EU's CSRD and ESRS? A: The ISSB and ESRS serve complementary but distinct purposes. ISSB focuses on financial materiality (information relevant to investors), while ESRS applies double materiality (also considering the company's impact on people and the environment). EFRAG and the ISSB have published interoperability mapping to help companies reporting under both frameworks minimize duplication.

Q: What level of assurance is required? A: The ISSB itself does not prescribe assurance levels, but many adopting jurisdictions require limited assurance at outset, with plans to transition to reasonable assurance. The IAASB's ISSA 5000 standard (published December 2024) provides the global framework for sustainability assurance engagements.

Q: Can small and medium enterprises (SMEs) be affected? A: Directly, most jurisdictions target large listed companies and financial institutions first. Indirectly, SMEs within the value chains of reporting entities will face data requests for Scope 3 calculations, making familiarity with ISSB requirements practically essential regardless of direct regulatory obligation.

Sources

• IFRS Foundation. (2023). "IFRS S1 General Requirements for Disclosure of Sustainability-related Financial Information." https://www.ifrs.org/issued-standards/ifrs-sustainability-standards-navigator/ifrs-s1-general-requirements/
• IFRS Foundation. (2023). "IFRS S2 Climate-related Disclosures." https://www.ifrs.org/issued-standards/ifrs-sustainability-standards-navigator/ifrs-s2-climate-related-disclosures/
• IOSCO. (2024). "IOSCO Endorsement of the ISSB Standards and Call for Action." https://www.iosco.org/library/pubdocs/pdf/IOSCOPD741.pdf
• PwC. (2024). "Global Investor Survey 2024: Sustainability Reporting Trust Gap." https://www.pwc.com/gx/en/issues/esg/global-investor-survey.html
• IFRS Foundation. (2025). "ISSB Adoption Guide: Jurisdiction Profiles and Implementation Progress." https://www.ifrs.org/use-around-the-world/issb-jurisdiction-profiles/
• IAASB. (2024). "International Standard on Sustainability Assurance (ISSA) 5000." https://www.iaasb.org/publications/international-standard-sustainability-assurance-5000
• Australian Treasury. (2024). "Climate-related Financial Disclosure: Legislation and Regulatory Framework." https://treasury.gov.au/consultation/c2024-466491
• UK Financial Conduct Authority. (2025). "UK Sustainability Reporting Standards: Policy Statement." https://www.fca.org.uk/publications/policy-statements/uk-sustainability-reporting-standards