ISSB S2 and ESRS E1 Interoperability Mapping at the Entity Reporting Boundary
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Climate Disclosure Dual-Filing May 2025  ·  10 min read

ISSB S2 and ESRS E1 Interoperability Mapping at the Entity Reporting Boundary

The IFRS Foundation and EFRAG interoperability mapping identifies approximately 70% content overlap between ISSB S2 and ESRS E1. These divergence in three areas: temporal scope of transition plan requirements, entity versus consolidated reporting boundary, and Scope 3 category treatment under limited assurance.

ISSB S2 divergence points ESRS E1 entity boundary Dual-filer disclosure CSRD equivalence assessment
Audience
Dual-filer disclosure officers — 2025 reporting cycle
Frameworks
IFRS S2 (ISSB) · ESRS E1 (CSRD)
Guidance Source
EFRAG / IFRS Foundation — 2 May 2024
EFRAG
IFRS
ESRS–ISSB Standards Interoperability Guidance
Joint Publication · May 2024
Read Full Publication

For entities managing obligations under both the IFRS Sustainability Disclosure Standards and the Corporate Sustainability Reporting Directive, the interoperability guidance published jointly by EFRAG and the IFRS Foundation on 2 May 2024 establishes a working framework for dual-filing. The guidance confirms that almost all disclosure requirements in IFRS S2 are present in ESRS, and that the financial materiality definitions in both frameworks converge on the same standard. The European Commission's technical consultation on equivalence for third-country issuers under CSRD, opened this month, makes the architectural gap operationally immediate for entities managing both obligations simultaneously.

01
Transition Plan Temporal Scope
ESRS E1 requires a plan consistent with limiting global warming to 1.5°C. ISSB S2 requires disclosure of plan existence and progress against stated targets with no Paris-alignment criterion specified.
02
Entity vs. Consolidated Boundary
ISSB S2 applies at the consolidated group level. CSRD applies to qualifying legal entities individually. Group-level S2 disclosures cannot serve as entity-level ESRS E1 disclosures for in-scope subsidiaries.
03
Scope 3 Category Treatment
ESRS E1 requires disclosure across all 15 Scope 3 categories with explicit omission statements and methodology notes. ISSB S2 applies a materiality screen before calculation, generating no omission documentation during the S2 process.

Temporal Scope of Transition Plan Requirements

ESRS E1 requires disclosure of a transition plan under paragraph E1.7 that is consistent with limiting global warming to 1.5°C. ISSB S2 requires disclosure of transition plan existence and progress against stated targets. An entity that prepares an S2-aligned transition plan referencing a sectoral decarbonisation pathway modelled at 2°C satisfies S2 requirements. The same disclosure does not satisfy ESRS E1.7.

The divergence does not appear in the interoperability mapping tables because it is an architectural requirement difference rather than a disclosure item difference. The mapping tables address paragraph-level alignment. The transition plan requirement difference operates at the level of the criterion that the plan must satisfy, a structural distinction that paragraph-level mapping does not surface.

For entities constructing a transition plan that satisfies both frameworks, the practical consequence is that the plan must be anchored to a 1.5°C-consistent scenario from the outset. A plan structured around a 2°C pathway and later adapted for ESRS produces a governance record of amendment that assurance providers will need to address. Building the plan to the more demanding criterion eliminates that documentary gap.

Documentation Architecture Note

Paragraph 34(e) of ESRS E1 requires disclosure of whether targets have been externally assured. ISSB S2 paragraph 34(a) requires disclosure of whether the target and methodology for setting the target has been validated by a third party. These requirements address different objects — assurance of the target itself versus validation of the methodology — and a single assurance engagement scope must be constructed to address both.

Entity versus Consolidated Reporting Boundary

ISSB S2 applies at the level of the reporting entity, which for most listed groups means the consolidated group. CSRD applies to legal entities above the applicable size threshold individually. A subsidiary of a US-headquartered multinational that produces a group-level climate disclosure aligned to TCFD and S2 cannot transpose that document as its ESRS E1 disclosure.

The governance structure documented, the scenario analysis scope, and the transition plan must all be prepared at the entity level. This produces a documentation requirement that group reporting structures do not generate. The governance body exercising oversight of climate risk at the subsidiary level may differ from the governance body described in the group disclosure. The scenario analysis inputs may reflect group-level assumptions that require translation to entity-level operations before they satisfy the ESRS disclosure criterion.

Commission Equivalence Assessment
Under the Commission's equivalence assessment, the treatment of the 30% divergence determines whether equivalence will be granted at the framework level or at the individual indicator level. Indicator-level equivalence creates a permanent dual-work requirement for entities where consolidated group reporting triggers CSRD obligations.
30%
Divergence
under review

The interoperability guidance addresses this boundary condition but does not specify the documentation requirements for subsidiaries operating under group disclosures. Entities in this position must construct entity-level disclosure documentation that draws on group-level analytical work without transposing it. The distinction between using group analytical outputs as inputs to entity-level disclosure versus transposing group disclosure as entity disclosure is the operative difference that the boundary condition creates.

Scope 3 Category Treatment under Limited Assurance

ISSB S2 requires Scope 3 disclosure using the GHG Protocol Corporate Value Chain Standard, with a materiality screen applied before calculation. ESRS E1 requires disclosure of Scope 3 across all 15 categories with an explicit statement of omissions and a methodology note for each category. The materiality screen under ESRS is applied post-calculation and requires a documented rationale for each category treated as below the materiality threshold.

Dimension ISSB S2 Approach ESRS E1 Approach
Materiality Screen Applied before calculation — categories below threshold need not be calculated Applied post-calculation — all 15 categories calculated, then screened with documented rationale
Omission Documentation Not required during S2 process for screened categories Explicit omission statement required for each excluded category Incremental
Methodology Notes Approach, inputs, and assumptions for calculated categories Methodology note required per category, including excluded categories
Assurance Scope Disclosure of extent of verification using verified inputs Mandatory assurance of sustainability statement; verification extent disclosed against mandatory assurance scope

Disclosure teams that build a Scope 3 inventory to S2 specification and then attempt ESRS transposition find that the omission documentation has not been generated during the S2 process and must be constructed retrospectively. The operational consequence is that inventory construction for dual-filers requires the ESRS methodology from the outset, treating all 15 categories as in-scope for calculation before applying the materiality screen.

Assurance Implications across Both Frameworks

Assurance providers applying ISAE 3410 to an entity producing both disclosures from a single evidence base are requesting supplementary documentation for the three divergence areas above. The documentation requirements are not identical between the two frameworks at the points of divergence, which means a single evidence pack structured around the interoperability overlap does not satisfy both assurance scopes without supplementary files covering the divergence areas.

The governance documentation gap at the entity boundary creates an assurance documentation requirement that group-level assurance engagements do not address. Assurance over the subsidiary's ESRS disclosure requires evidence of the subsidiary-level governance structure and decision-making processes. Where a group assurance engagement has produced evidence about the group governance structure, that evidence functions as contextual background for the subsidiary engagement rather than as primary evidence.

The Scope 3 omission documentation gap creates a specific evidence requirement. ESRS E1 paragraph AR46 requires a list of Scope 3 greenhouse gas emissions categories included in and excluded from the inventory with a justification for excluded categories. Where this justification has not been documented during inventory construction, the assurance engagement must address the gap before limited assurance over the Scope 3 disclosure can proceed.

Approach for Dual-Filing Documentation

The interoperability guidance is not a statement of equivalence. The Commission's equivalence assessment is a separate regulatory process, and its outcome determines whether the 30% divergence generates ongoing parallel documentation requirements or can be resolved through a mapped filing approach. Until that determination is made, entities filing under both frameworks must maintain documentation that satisfies each framework's requirements at the points of divergence.

The three divergence areas each requires documentation that must be generated during the primary analysis process rather than prepared at the transposition stage. Transition plan 1.5°C alignment must be embedded in the planning assumptions. Entity-level governance documentation must be produced at the entity level, not derived from group documentation. Scope 3 omission rationale must be generated during inventory construction. The operational implication is that the ESRS-compliant methodology functions as the baseline process for dual-filers, with S2-specific outputs derived from that baseline rather than the reverse.