ISSB IFRS S1 and S2 Implementation Guide for US Companies

The global sustainability disclosure landscape is converging around two standards. IFRS S1 and IFRS S2, developed by the International Sustainability Standards Board (ISSB), are rapidly becoming the baseline that regulators, investors, and capital markets use to evaluate how companies manage sustainability-related risks and opportunities.

As of early 2026, jurisdictions representing over half of global GDP have adopted or are in the process of adopting these standards. S&P Global reports that 21 jurisdictions have already gone live, with 16 more on a formal adoption pathway.

U.S. companies occupy a complicated position. There is no federal ISSB mandate and the SEC abandoned its own climate disclosure rule in March 2025. But that federal vacuum does not mean irrelevance.

California’s SB 253 and SB 261 create binding state-level obligations for large companies doing business in the state. IFRS S2 is fully aligned with the TCFD framework that SB 261 references.

Any U.S. company with operations or subsidiaries in the UK, Canada, Hong Kong, Australia, or other adopting jurisdictions faces direct compliance requirements. And institutional investors are increasingly demanding ISSB-aligned disclosures as a condition of capital access.

This ISSB IFRS S1 S2 guide provides a practical implementation roadmap for U.S. companies. Every section maps to the four-pillar disclosure structure, connects to established enterprise risk management frameworks, and identifies the specific actions needed to move from gap analysis to audit-ready reporting.

Understanding IFRS S1 and S2: Structure and Scope

IFRS S1 (General Requirements for Disclosure of Sustainability-related Financial Information) sets the overarching framework. IFRS S2 (Climate-related Disclosures) is the first topic-specific standard built on that foundation.

The two standards are designed to be applied together. IFRS S1 establishes the conceptual principles: what counts as material, how to connect sustainability disclosures to financial statements, and how to use industry-specific guidance from the SASB Standards.

IFRS S2 provides the detailed requirements for climate-related risks, opportunities, scenario analysis, GHG emissions, and transition planning.

Both standards follow the four-pillar structure inherited from the TCFD: Governance, Strategy, Risk Management, and Metrics and Targets.

The ISSB designed these as investor-focused standards using financial materiality only, not the double materiality concept used by the EU’s CSRD.

A sustainability risk or opportunity is material under IFRS S1 if omitting, misstating, or obscuring information about it could reasonably be expected to influence the decisions of primary users of general-purpose financial reports. This definition aligns closely with SEC materiality concepts, making the transition more intuitive for U.S.-based preparers.

IFRS S1 vs. IFRS S2: Key Differences

The Four-Pillar Disclosure Framework

The four pillars form the backbone of every ISSB disclosure. U.S. companies already familiar with TCFD reporting will recognize the structure.

The ISSB comparison table (updated November 2024) confirms that IFRS S2 incorporates all TCFD recommendations, with some areas requiring deeper disclosure than TCFD. Below is a detailed breakdown of each pillar with the specific disclosure requirements most relevant to U.S. preparers.

Pillar 1: Governance

Disclose the governance processes, controls, and procedures your company uses to monitor and manage sustainability-related (S1) and climate-related (S2) risks and opportunities.

This includes identifying the governance body or individual responsible for oversight, describing how their responsibilities are reflected in terms of reference or mandates, explaining how the board ensures appropriate skills and competencies are available, and detailing how often the body is informed about sustainability risks. Connect this to your existing GRC framework and board risk committee charter.

Pillar 2: Strategy

Disclose how sustainability and climate risks and opportunities affect your business model, value chain, strategy, and financial planning.

Under IFRS S2, this includes a description of climate-related risks and opportunities that could reasonably be expected to affect cash flows, access to finance, or cost of capital over the short, medium, and long term.

Companies must also disclose the current and anticipated effects on financial position, performance, and cash flows, and describe the resilience of their strategy using climate scenario analysis. IFRS S2 requires scenario analysis to assess climate resilience, using at least a scenario consistent with the latest international agreement on climate change (Paris Agreement).

Pillar 3: Risk Management

Disclose the processes used to identify, assess, prioritize, and monitor sustainability and climate risks and opportunities. Describe how these processes are integrated into the overall risk management process.

The ISSB expects companies to explain how they determine the relative significance of sustainability risks compared to other risks, what input parameters they use, and whether the processes have changed compared to prior periods. This pillar maps directly to ISO 31000 and COSO ERM risk identification and assessment steps.

Pillar 4: Metrics and Targets

Disclose the metrics used to measure and monitor sustainability and climate risks and opportunities, plus any targets set and progress against them.

IFRS S2 requires three categories of climate metrics: cross-industry metrics applicable to all companies (GHG emissions Scope 1, 2, 3; climate-related transition and physical risks as a percentage of assets or revenues; internal carbon price if used; remuneration linked to climate), industry-based metrics derived from SASB Standards applicable to the company’s sector, and company-specific metrics used by the board or management to track progress. GHG emissions must be measured using the GHG Protocol Corporate Standard (Scope 1 and 2) and Corporate Value Chain Standard (Scope 3).

The U.S. Regulatory Context: Why ISSB Matters Without a Federal Mandate

The SEC adopted climate disclosure rules in March 2024 but excluded Scope 3 emissions from the final version and limited Scope 1/2 disclosure to material emissions.

The SEC then withdrew defense of even that scaled-back rule in March 2025, and the Eighth Circuit litigation remains in abeyance as of September 2025. Acting Chairman Uyeda called the rule “deeply flawed.” The OCC, FDIC, and Federal Reserve all withdrew from the NGFS in early 2025.

That federal retreat does not eliminate climate disclosure obligations for U.S. companies. California’s SB 253 requires Scope 1 and 2 emissions reporting starting January 2026 and Scope 3 by January 2027 for companies with revenues over $1 billion doing business in the state. SB 261 requires climate risk disclosures aligned with the TCFD framework for companies with revenues over $500 million.

IFRS S2 is fully aligned with and supersedes TCFD, meaning a company reporting under IFRS S2 can satisfy SB 261 requirements without creating a separate report. Companies with global operations face direct mandates in adopting jurisdictions: the UK’s draft sustainability standards (published June 2025) are based on ISSB, Hong Kong’s became effective August 2025, and Chile’s are mandatory from January 2026.

Market-driven pressure is equally compelling. Harvard Law School’s analysis of 2025 sustainability reporting trends found that IFRS S2 is emerging as the common reference point globally, with SASB adoption also rising as it integrates into the ISSB framework. Institutional investors managing trillions of dollars increasingly expect ISSB-aligned disclosures as a baseline for capital allocation decisions.

U.S. companies that delay implementation risk competitive disadvantage in global capital markets and may find themselves scrambling to comply when their next jurisdiction-specific obligation triggers.

U.S. Compliance Triggers for ISSB Standards

Step-by-Step Implementation for U.S. Companies

The ISSB designed the standards to be proportionate: companies apply requirements in a manner appropriate to their circumstances, using reasonable and supportable information available without undue cost or effort.

The following implementation steps reflect practical experience from the first full year of ISSB reporting globally.

Step 1: Conduct a Gap Analysis

Map your current sustainability disclosures (TCFD, CDP, GRI, SASB, SEC filings) against IFRS S1 and S2 requirements. Identify gaps in each of the four pillars. Most U.S. companies already reporting under TCFD will find significant overlap in Governance and Strategy.

The largest gaps typically appear in: Scope 3 emissions measurement (especially Category 15 for financial institutions), climate scenario analysis (required under IFRS S2 but not consistently performed), financial effects quantification (connecting sustainability risks to cash flow and balance sheet impacts), and industry-based SASB metrics (required consideration under S1, required disclosure under S2).

Build a gap register that maps each disclosure requirement to the responsible internal function, current data availability, and remediation timeline. Structure this like your existing risk register.

Step 2: Establish Governance and Accountability

IFRS S1 requires disclosure of the governance body responsible for sustainability oversight. Before you can disclose it, you need to build it. Assign board-level responsibility for sustainability risk oversight (risk committee or dedicated sustainability committee).

Define management-level accountability for data collection, analysis, and disclosure preparation. Ensure the governance body has access to appropriate skills and competencies.

Establish reporting cadence (at minimum aligned with financial reporting cycles). Apply the Three Lines Model: first line owns data, second line validates methodology and thresholds, third line provides assurance.

Step 3: Identify Material Sustainability and Climate Risks

Use IFRS S1’s materiality guidance to identify which sustainability-related risks and opportunities are material to your company. Start with the SASB Standards for your industry to identify sector-specific topics. Cross-reference against IFRS S2’s climate-specific requirements.

Engage cross-functional teams (finance, operations, legal, sustainability, procurement) to identify risks across the value chain. Document the process, including how you determined relative significance.

This step parallels a standard risk assessment process. The output is a list of material sustainability risks and opportunities, each linked to a specific time horizon (short, medium, long term) and an estimated financial effect.

Step 4: Build the Data Architecture

IFRS S2 requires specific quantitative disclosures that many U.S. companies do not currently track: GHG emissions across all material Scope 3 categories, climate-related assets and revenues exposed to physical and transition risk, internal carbon pricing if used, and remuneration tied to climate targets.

Audit your current data infrastructure. Identify which systems capture the required data points and where manual processes or estimation are needed. Prioritize automation for repeatable data collection.

Align your ERM technology stack with sustainability data needs. Remember that IFRS S2 requires GHG emissions measurement using the GHG Protocol, and financial institutions must consider the PCAF methodology for financed emissions (Category 15).

Step 5: Perform Climate Scenario Analysis

IFRS S2 requires companies to assess the resilience of their strategy and business model to climate-related changes, circumstances, and uncertainties, using scenario analysis that is commensurate with the company’s circumstances.

At minimum, use a scenario consistent with the Paris Agreement and at least one additional scenario representing greater physical risk. NGFS scenarios provide a ready-made framework.

Select Net Zero 2050 (orderly transition) and Current Policies (high physical risk) as a starting pair, then add Delayed Transition (disorderly) for comprehensive coverage. Connect scenario outputs to financial metrics your board already uses. See our deep dive on climate risk scenario analysis for a full methodology.

Step 6: Prepare Disclosures and Seek Assurance

Structure your disclosures around the four pillars. Use cross-referencing to avoid duplication between S1 and S2 (if governance processes are the same for both, disclose once).

Connect sustainability disclosures to financial statements to show how material risks translate to financial effects. Apply the year-one transitional reliefs: focus on climate only (S2), defer Scope 3 if needed, publish sustainability disclosures after financial statements if required. Plan for assurance from Day 1.

The ISSB expects sustainability disclosures to be subject to the same rigor as financial reporting. Build internal audit-ready documentation, including data lineage, methodology choices, management judgments, and control evidence.

Integrating ISSB Standards with Enterprise Risk Management

The four-pillar structure of IFRS S1 and S2 maps cleanly onto established ERM frameworks.

The Risk Management pillar explicitly requires companies to describe how sustainability risk identification and assessment integrates with the overall risk management process. This is not a suggestion.

Companies that maintain parallel sustainability and ERM processes will struggle with both consistency and efficiency.

Connecting IFRS S2 climate metrics to key risk indicators creates ongoing monitoring capability. Rather than preparing climate disclosures once per year, embed ISSB-derived metrics into the KRI dashboard with quarterly tracking and RAG thresholds aligned with your risk appetite statement.

ISSB vs. CSRD: Interoperability for Global Companies

U.S. companies with European operations often need to satisfy both ISSB and CSRD/ESRS requirements. The good news: EFRAG and the ISSB published joint interoperability guidance in May 2024. The key difference is materiality: ISSB uses financial materiality only, while CSRD uses double materiality (financial plus impact).

A company reporting under both will need to extend its ISSB-focused assessment to include impact materiality for CSRD purposes. The disclosure structure aligns across the four pillars.

ESRS E1 (climate) corresponds closely to IFRS S2, and EFRAG’s ongoing ESRS simplification is expected to further improve alignment. Build a single data architecture that captures all required data points, then filter outputs for each framework.

Implementation Roadmap

Challenges and How to Avoid Them

Looking Ahead: Trends for 2026–2028

The ISSB’s strategic priorities through 2026 focus squarely on implementation support. The board is convening its Transition Implementation Group (TIG) to address companies’ application questions, developing educational materials, and delivering a comprehensive capacity-building program.

SASB Standards are being progressively enhanced and aligned with ISSB language, with nine industry standards already in exposure draft and more coming through 2026.

Nature-related disclosures are next. The ISSB has signaled that it will build on the Taskforce on Nature-related Financial Disclosures (TNFD) framework to develop new standards addressing biodiversity, water, and ecosystem risks.

The TNFD will complete its sector guidance by Q3 2026, mirroring the path TCFD took before being absorbed into the ISSB framework. Companies that build flexible disclosure architectures now will be able to incorporate nature-related requirements without starting over.

Convergence between ISSB and CSRD is accelerating. EFRAG’s ongoing ESRS simplification, combined with the ISSB’s December 2025 amendments to S2, is narrowing the gap between the two frameworks.

Companies reporting under both will increasingly benefit from a single data collection and analysis process that feeds two disclosure outputs. The risk quantification capabilities needed for ISSB financial effects disclosure and CSRD double materiality assessment overlap substantially.

U.S. companies that adopt ISSB standards proactively, even absent a federal mandate, will be positioned for three advantages: meeting state and international compliance obligations through a single framework, satisfying investor expectations for decision-useful sustainability information, and building the data infrastructure and governance capabilities that any future federal requirement would demand. The cost of starting late far exceeds the cost of starting now with a structured enterprise risk management framework approach.

Ready to implement ISSB IFRS S1 and S2? Visit riskpublishing.com/services for implementation templates, gap analysis tools, and expert consulting support. Need help connecting ISSB disclosure to your ERM framework? Contact our team to discuss your roadmap.

References

1. IFRS Foundation: Introduction to ISSB and IFRS Sustainability Disclosure Standards — Official overview of IFRS S1 and S2 structure, scope, and application

2. IFRS Foundation: ISSB Issues Targeted Amendments to IFRS S2 (December 2025) — Details of GHG emissions disclosure relief for financial institutions

3. S&P Global: Where Does the World Stand on ISSB Adoption? (January 2026) — Quarterly tracker of global ISSB adoption by jurisdiction

4. S&P Global: ISSB Adoption Tracker (September 2025) — Detailed analysis of jurisdictional adoption status and California SB 253/261

5. Harvard Law Forum: 2025 Sustainability Reporting Global Trends — Analysis of ISSB, GRI, and SASB adoption trends across regions

6. KPMG: Illustrative Disclosures for IFRS Sustainability Standards — Practical disclosure examples across all four pillars

7. KPMG Switzerland: IFRS S1 and S2 Overview — Comparison of S1 vs. S2 requirements and TCFD alignment

8. Grant Thornton: Overview of IFRS S1 and IFRS S2 — Summary of key requirements and transitional relief provisions

9. BSI Group: Understanding IFRS S1 and S2 for Climate Risk Reporting — Practical implementation steps for U.S. companies

10. Sodali & Co: One Year In — How Companies Are Navigating IFRS Sustainability Reporting — Analysis of first-year adoption trends and patterns

11. IFRS Foundation: ISSB Proposes Comprehensive Review of Priority SASB Standards (July 2025) — SASB enhancement program and alignment with ISSB Standards

12. Mitiga Solutions: What Are IFRS S1 and S2? Key Differences, Deadlines, and Applicability — Comprehensive guide to S1/S2 scope, adoption timeline, and SB 261 alignment

13. ESG Reporting Hub: IFRS S1 and S2 General Overview — Detailed breakdown of disclosure requirements by pillar

14. Aligned Incentives: ISSB Standards — A Guide for Companies — Practical guide covering materiality, value chain, and transitional relief

15. Harvard Law Forum: Regulatory Climate Shift — SEC Climate Disclosure Updates — Current status of SEC climate rule litigation and state-level alternatives

Chris Ekai

Chris Ekai is a Risk Management expert with over 10 years of experience in the field. He has a Master’s(MSc) degree in Risk Management from University of Portsmouth and is a CPA and Finance professional. He currently works as a Content Manager at Risk Publishing, writing about Enterprise Risk Management, Business Continuity Management and Project Management.