First ISSB Sustainability Report Checklist Mexico 2026: Step-by-Step for Listed Companies
If your company is listed on the BMV or BIVA, your first IFRS S1/S2-aligned sustainability report is due in 2026 — covering FY2025 data. That means the clock is already running. This checklist walks you through every phase you must complete before you file, from governance setup to data collection to report review. Use it to assess where you stand today and what gaps remain.
Who Must File and When
Mexico's CNBV (Comisión Nacional Bancaria y de Valores) made IFRS S1 and IFRS S2 mandatory for all issuers listed on the BMV and BIVA as of January 29, 2025. This makes Mexico the first country in North America to mandate ISSB standards. The requirements cover approximately 86% of the IPC's market capitalization.
Key regulatory milestones:
2025 (now): Collect FY2025 data in an IFRS S1/S2-compliant manner
2026: File first sustainability report (FY2025 data) alongside annual financial report
2027: Limited assurance on FY2026 sustainability data — auditors will scrutinize your processes
2028+: Reasonable assurance (same level as financial statements) for FY2027 data onward
Note: If your company also reports under NIF (Mexican Financial Reporting Standards), you simultaneously face NIS A-1 and NIS B-1 obligations from CINIF — which require reporting 30 IBSO indicators covering all companies, not just listed ones.
The Complete Checklist: 8 Phases
Phase 1: Governance Setup
IFRS S1 requires you to disclose how your board oversees climate-related risks and opportunities. Governance is the first pillar — and auditors will ask for documentation.
Assign board-level responsibility for sustainability oversight (specific committee or director)
Document how frequently the board reviews climate and sustainability topics
Define management roles (CFO, Head of Sustainability, IR) and their responsibilities in data collection
Create an internal policy linking sustainability risk management to financial planning
Phase 2: Materiality Assessment (IFRS S1)
IFRS S1 uses a financial materiality lens: you must disclose sustainability-related risks and opportunities that could reasonably be expected to affect your enterprise value or cash flows.
Map your industry using SASB Industry Standards (applicable to your SICS code)
Identify sustainability topics material to your business model over short, medium, and long horizons
Document your materiality assessment process (who was consulted, what sources used)
Confirm climate is a material topic (required for all IFRS S2 filers)
Phase 3: Climate Risk & Opportunity Identification (IFRS S2)
IFRS S2 requires identifying both physical risks (floods, heat stress, water scarcity) and transition risks (carbon pricing, stranded assets, regulatory changes) that could affect your business.
Catalog physical risks by asset location (use IPCC or NGFS regional data for Mexico)
Catalog transition risks: regulatory (SEMARNAT, CNBV), market, technology, and reputational
Identify climate-related opportunities (renewable energy, green financing, sustainable products)
Document the time horizons over which each risk or opportunity may materialize
Phase 4: Climate Scenario Analysis
IFRS S2 requires you to assess your business strategy's resilience under different climate scenarios — typically one below 2°C pathway and one higher warming scenario. For your first report, CNBV allows simplified scenario analysis.
Select at least two climate scenarios (e.g., NGFS Net Zero 2050 and Current Policies)
Map how each scenario affects your key assets, revenue streams, and cost structure
Quantify financial impacts where possible (at least qualitatively describe them for year 1)
Document your scenario methodology and sources (IPCC, IEA, NGFS)
Phase 5: GHG Emissions Data Collection (Scope 1, 2, and 3)
This is where most companies struggle. Only 50% of Mexican companies currently measure Scope 1 and 2 emissions. Only 25% measure Scope 3. Yet IFRS S2 requires all three — with a Scope 3 transition relief available until end of 2026 for your first reporting year.
Scope 1: Direct emissions from owned/controlled sources (boilers, fleets, refrigerants, industrial processes)
Scope 2: Indirect emissions from purchased electricity, heat, and steam (use CFE emission factors for Mexico)
Scope 3: Value chain emissions across 15 categories (business travel, purchased goods, investments, end-of-life treatment)
Establish a data collection process from subsidiaries, operations, and key suppliers
Document emission factors used (GHG Protocol, IPCC AR6, or SEMARNAT factors)
Create an audit trail: every data point must be traceable to a source document
Phase 6: Metrics, Targets & Industry-Specific Disclosures
Report cross-industry metrics: absolute GHG emissions, percentage from renewables, climate-related CAPEX
Apply SASB industry-specific metrics relevant to your sector
Disclose existing GHG reduction targets (or explain why none have been set)
Include how you plan to achieve your targets and what milestones you track
Phase 7: Internal Controls & Audit Readiness
Limited assurance begins with FY2026 data. That means auditors will review your FY2026 processes — which you need to design and document now, in 2025, while collecting FY2025 data.
Document every data source, calculation methodology, and assumption in a central repository
Implement data validation controls (no unsupported manual entries, version history, approvals)
Define roles and segregation of duties in your data collection process
Run a dry-run internal audit before filing to identify data gaps and inconsistencies
Brief your external auditor (Big Four or equivalent) on your methodology early in the process
Phase 8: Report Drafting, Review & Filing
Structure your report using the four IFRS S1 pillars: Governance, Strategy, Risk Management, Metrics & Targets
Integrate disclosures into your annual report or file as a standalone sustainability report per CNBV guidance
Include comparative data (prior year if available) to show trend and progress
Legal review: check all disclosures for greenwashing risk and CNBV compliance
Board approval of final report before filing
Quick Self-Assessment: Where Does Your Company Stand?
Use this quick table to score your current readiness:
Governance documented → Phase 1 complete
Materiality assessment completed with SASB → Phase 2 complete
Climate risks cataloged by type and time horizon → Phase 3 complete
Two or more climate scenarios analyzed → Phase 4 complete
Scope 1 and 2 measured with audit trail; Scope 3 in progress → Phase 5 in progress
GHG targets defined and documented → Phase 6 complete
Internal controls in place with documented methodology → Phase 7 complete
Draft report reviewed by legal and board → Phase 8 complete
5 Common Mistakes to Avoid in Your First ISSB Report
Treating it like a GRI report. IFRS S1/S2 uses financial materiality only — not double materiality like GRI. Don't disclose topics that don't affect enterprise value.
Collecting data in spreadsheets. Manual collection from 20+ cost centers via email is not audit-ready. Auditors will question data lineage.
Skipping scenario analysis because it's 'too complex.' CNBV requires it even in year one. A qualitative analysis with two scenarios is acceptable for 2026.
Not involving the CFO and auditor early. Sustainability data will face the same scrutiny as financial statements by 2027. Loop in your finance and audit team from day one.
Confusing IFRS S2 with NIS B-1. If you're both a BMV issuer and a NIF reporter, you have overlapping but distinct obligations. IFRS S2 covers climate-specific disclosures; NIS B-1 covers 30 basic IBSO indicators for all ESG dimensions.
How Climatta Helps You Check Every Box
The core challenge in all eight phases is the same: collecting accurate, traceable data from dozens of internal and external sources in a way that survives an audit. Climatta was built specifically for this.
Automated data collection from your ERP, subsidiaries, and suppliers — no spreadsheets
Pre-built templates mapped to IFRS S1/S2, NIS B-1, and the 30 IBSO indicators
Audit trail for every data point: source, methodology, calculation, approver
CNBV-aligned reporting output — in Spanish, for the Mexican regulatory context
Built for assurance readiness from day one — not retrofitted after an auditor finds gaps
Frequently Asked Questions
When exactly is the deadline for the first ISSB report in Mexico?
The first report covers FY2025 data and must be filed in 2026, alongside your annual financial statements. The exact filing date follows your existing annual report calendar with the CNBV. FY2025 data collection is happening right now — which is why preparation cannot wait.
Is Scope 3 mandatory for the first report?
IFRS S2 requires Scope 3 disclosures. However, the standard includes a transition relief: companies can omit Scope 3 in their first year of application (FY2025) if the data is not yet available. That relief expires at the end of 2026, so you must have Scope 3 systems in place for FY2026 data.
Does IFRS S2 replace GRI for Mexican companies?
No. IFRS S2 is a mandatory regulatory requirement from CNBV. GRI remains a voluntary global framework some companies use for broader sustainability reporting. They have different materiality definitions (financial vs. double materiality) and different audiences. Many companies will file both.
What happens if our company misses the CNBV deadline?
Non-compliance with CNBV disclosure requirements can result in administrative sanctions, reputational damage, and potential impacts on your listing status. Beyond regulatory penalties, ESG rating agencies (MSCI, Sustainalytics) will flag missing disclosures, which can affect your score and access to ESG-focused institutional capital.
What is the difference between limited and reasonable assurance for sustainability data?
Limited assurance (required from 2027 for FY2026 data) means your auditor concludes nothing came to their attention indicating the data is materially misstated — a negative statement. Reasonable assurance (required from 2028 for FY2027 data) is a positive statement that the data is free from material misstatement, equivalent to the assurance level for financial statements. The latter requires significantly more rigorous controls and documentation.
Does this checklist also cover NIS B-1 obligations?
This checklist focuses on IFRS S1/S2 for listed companies. If your company also reports under NIF (which most Mexican companies do), you additionally need to comply with NIS A-1 and NIS B-1 from CINIF, which require 30 IBSO basic sustainability indicators. Listed companies have both obligations simultaneously.