ISSB Reporting Software: How to Scale IFRS S1 and S2 Across Jurisdictions Without Losing Control of Scope 3 Data

Last updated: 21 October 2026

ISSB reporting software is a platform that collects, controls and reports the data behind IFRS S1 and IFRS S2 disclosures. It works across every entity, country and reviewer in a group. Scope 1 and 2 are the easy part. Scope 3 is where multi-country reporting usually breaks.

This guide explains how to scale ISSB reporting across jurisdictions in 2026. It covers supplier data, estimates, operating-country differences, evidence, climate scenarios and approvals. It reflects the December 2025 amendments to IFRS S2 and adoption news up to October 2026. Software selection should also reflect assurance needs: reviewers must be able to trace reported figures to their sources, methods and approvals, rather than rely on the final disclosure alone.

Where does ISSB adoption stand in 2026?

ISSB adoption is growing, but it happens one jurisdiction at a time. The ISSB issued IFRS S1 and IFRS S2 in June 2023. They are effective for annual periods beginning on or after 1 January 2024, while mandatory application depends on jurisdictional rules. As of 22 July 2026, 35 jurisdictions had adopted them on a voluntary or mandatory basis, according to S&P Global research.

A multinational group therefore reports against one baseline with many local versions. Start dates differ. Reliefs differ. Some regulators add their own changes. The table shows a few recent examples.

Always confirm the current local requirement before you file. Dates and reliefs can change.

Aligning ISSB and ESRS reporting in one system

The IFRS Foundation and EFRAG’s interoperability guidance identifies substantial alignment in climate disclosures. That creates opportunities to reuse information, but it does not make the two reporting frameworks interchangeable. Mapping must use the versions applicable to the reporting period and jurisdiction.

ISSB materiality focuses on information relevant to investors and other capital providers. ESRS also considers the organization’s impacts on people and the environment. An impact can therefore require an ESRS disclosure even when the corresponding information is not material under the ISSB lens.

In shared software, retain separate financial-materiality and impact-materiality assessments, with their rationale, evidence, owners and approvals. Link them to a common register of impacts, risks and opportunities. Do not use a single materiality flag to switch disclosures on or off across both frameworks.

Maintain a mapping register that records each disclosure requirement, standard version, reporting boundary, metric definition and source dataset. Identify what can be reused, what needs adjustment and what requires additional narrative. Shared GHG Protocol inputs can reduce duplication, but differences in boundaries, measurement choices and required disclosures still need reconciliation.

For example, a group can reuse an approved electricity dataset while preparing separate outputs for each framework. The reporting team should document any adjustments and confirm that the associated materiality decisions and narrative meet each framework’s requirements.

What is the difference between Scope 1 and 2 and Scope 3 data under IFRS S2?

Scope 1 is direct emissions from owned or controlled sources; Scope 2 is emissions from generation of purchased or acquired electricity, steam, heating and cooling consumed by the entity. Scope 3 data comes from the value chain, so the group does not control it. IFRS S2 requires absolute gross emissions for all three scopes. It points to the GHG Protocol for measurement, unless a jurisdiction requires another method.

Why does Scope 3 data break when you scale across countries?

Scope 3 breaks at scale because every country team solves the same problem in a different way. Five issues show up again and again.

Managing supplier fatigue and missing responses

A common questionnaire helps, but repeated requests from multiple customers can overwhelm suppliers. Smaller suppliers and those further down the chain may lack emissions systems or have little incentive to respond. A reporting process needs a defined route for incomplete responses as well as complete ones.

Prioritize outreach by likely emissions significance and data gaps. Reuse valid supplier information where scope and reporting period match, and ask only for missing fields.

Evaluate request tracking, scheduled reminders and escalation to procurement owners. Automated follow-ups should be proportionate and coordinated so different country teams do not duplicate requests.

Where direct data is unavailable, evaluate transparent estimation options such as activity-based proxies, spend-based methods or documented sector averages. Record geography, reporting period, factor source, assumptions and uncertainty.

Keep estimated or imputed values visibly separate from supplier-reported figures. Require approval of the method and retain the original estimate when better data replaces it.

Track response rates and the share of estimated emissions by category, alongside a plan to improve the most consequential gaps. A higher response rate alone does not establish better emissions coverage.

These are software evaluation and process-design criteria. They are not claims that every platform offers these functions, or that an estimate becomes acceptable simply because software generated it.

What does IFRS S2 require for Scope 3 estimates?

IFRS S2 asks you to use all reasonable and supportable information available at the reporting date without undue cost or effort. That wording is the core of the Scope 3 measurement framework. It brings flexibility, and it brings a duty to explain your choices.

• You do not have to collect data from everyone in your value chain.
• Where possible, prioritise data that is directly measured and specific to the activity.
• Secondary data and industry averages are allowed when that is what you can reasonably obtain.
• Disclose the extent of activity-specific and verified inputs, alongside methods and assumptions.
• In the first annual reporting period of applying IFRS S2, companies may leave out Scope 3 emissions and must say that they used the relief. Some jurisdictions change or extend this relief.
• Financial institutions may limit Scope 3 Category 15 to financed emissions under the December 2025 amendments. Those who report Category 15 must also show the financed emissions subtotal.

The practical lesson is simple. Treat each Scope 3 figure as a record. It needs a method, a source, a quality flag and an owner. Read more in the IFRS Foundation proportionality factsheet and the IFRS S2 amendments page.

How should a group handle climate scenario analysis under IFRS S2?

IFRS S2 requires companies to use climate-related scenario analysis to assess climate resilience, with an approach that fits their circumstances. The standard allows proportionate methods, including qualitative analysis where it suits the company.

For a multi-country group, a simple model works best:

• Set scenarios and time horizons once at group level.
• Let local teams add physical-risk and policy inputs for their own sites and markets.
• Keep assumptions, versions and sign-offs in one controlled place.
• Link scenario results to value-chain hot spots, so Scope 3 data informs the resilience story.

Who should own what: local entities or the group?

The group should own the rules. Local entities should own the facts. This split keeps methods consistent while the people closest to the data stay accountable for it.

The review chain should distinguish preparation, management approval and independent assurance. Local contributors supply data; local and group reviewers resolve exceptions; management approves the disclosures. Internal audit and external assurance interact with this process without taking ownership of management’s reporting decisions.

Data lineage and preparation for assurance

A usable lineage record lets a reviewer move from a disclosed total to the contributing entities, calculations and original evidence. An activity log alone is insufficient if it records an edit without preserving the source or calculation behind it.

• Source retention: preserve original files with stable identifiers, submission dates, entity and period metadata, and access-controlled retention. Replacing a file should create a new version rather than erase the previous source.
• Transformation records: capture units, conversions, allocation rules, emission factors and their versions. Retain the mapping from source fields to calculated metrics and disclosure outputs so a calculation can be reproduced.
• Change history: evaluate append-only or tamper-evident logging, including administrator activity, old and new values, timestamps and reasons for changes. Ask vendors to demonstrate any claim of immutability, including retention and access controls.
• Review evidence: link exceptions, reviewer questions, resolutions and approvals to the affected metric. Retain the approved reporting snapshot and show how later corrections affect downstream totals.
• Controlled access: evaluate read-only evidence access or export packages for assurance teams, while retaining management ownership of data and preventing reviewers from changing the reporting record.

Preparing for limited and reasonable assurance

ISSA 5000 addresses both limited and reasonable assurance. Both require sufficient appropriate evidence, but reasonable assurance provides a higher level of assurance and generally involves more extensive procedures. The nature, timing and extent of work depend on the engagement and assessed risks; software does not determine the practitioner’s conclusion.

Build reproducible calculations and evidence retention into the process from the outset. Where reasonable assurance is required or planned, assess whether controls can be tested over time, exceptions are resolved and reported populations can be reconciled to source records. Do not assume every jurisdiction mandates a progression from limited to reasonable assurance.

Internal audit can assess the design and operation of controls and track remediation. The external assurance provider independently determines procedures and evaluates evidence. Management remains responsible for the disclosures, methods and approvals.

Architecture checklist for multi-jurisdiction ISSB tools

Use the following criteria to evaluate a platform. Ask for a demonstration using a representative supplier file, a calculation change and a framework-specific disclosure, rather than relying only on a feature list.

• A common data model with entity, period, boundary and framework-specific metadata.
• Version-controlled methods and emission factors, with reproducible calculation records.
• Coordinated supplier requests, response tracking and governed estimation options.
• Clear provenance and quality flags for measured, supplier-reported and estimated values.
• Retained source files and traceable links between evidence, transformations and disclosures.
• Validation rules, exception resolution and reconciliation before consolidation.
• Role-based preparation, review and approval, with controlled access for assurance work.
• Climate scenarios and framework mappings linked to approved assumptions and data.
• Tamper-evident change history, approved snapshots and traceable corrections.

Applying these requirements with EcoActive

These requirements provide a practical basis for evaluating a unified reporting platform. EcoActive’s AI-native Financial and ESG Disclosure Management platform supports connected emissions, value-chain and climate-scenario work, with evidence, reviews and approvals in a governed reporting process.

An illustrative multi-country reporting workflow

A group collecting local emissions data can organize submissions, supporting evidence and review responsibilities in a connected process. Group teams can review the information behind disclosures while local teams remain accountable for their inputs. This illustrates how the capabilities described here can support reporting coordination; it is not a measured customer outcome.

What to validate in a demonstration

Ask the team to trace a sample figure from its source through review and disclosure, show how a correction is recorded, and explain how evidence can be made available for assurance. Confirm the specific configuration for supplier follow-ups, estimation, retention and framework mappings before treating those capabilities as established.

Frequently asked questions

What is ISSB reporting software?

ISSB reporting software collects, validates and reports the data needed for IFRS S1 and IFRS S2 disclosures. Strong platforms add workflows, evidence links, approvals and audit trails. They help groups apply one method across many entities and countries.

How does EcoActive support ISSB reporting?

EcoActive’s AI-native disclosure management platform connects emissions data, value-chain information, climate-scenario inputs, and disclosures within one governed environment. Teams can maintain supporting evidence, calculation methodologies, reviews, and approvals to support IFRS S1 and IFRS S2 reporting. Agentic AI helps coordinate repeatable reporting activities, while decisions and final approvals remain under human control.

Are IFRS S1 and IFRS S2 mandatory?

They are mandatory only where a jurisdiction requires them. Some jurisdictions mandate them, some permit voluntary use, and others publish local standards based on them. Check the rules in each country where your group reports.

Do companies have to report Scope 3 emissions in the first year?

Not always. IFRS S2 includes a transition relief that lets companies skip Scope 3 in the first annual reporting period of applying it. Companies must disclose that they used the relief. Local regulators may change or extend it.

Can companies estimate Scope 3 emissions under IFRS S2?

Yes. IFRS S2 allows estimates, secondary data and industry averages. Companies must use reasonable and supportable information available without undue cost or effort. They must also disclose their methods, estimate sources and whether inputs were verified.

What changed in the December 2025 IFRS S2 amendments?

The ISSB issued targeted amendments on 11 December 2025. They let entities limit Scope 3 Category 15 to financed emissions. They also clarify jurisdictional relief from the GHG Protocol method and from the latest IPCC global warming potential values. They apply from 1 January 2027, with early application permitted.

Can one emissions dataset support ISSB and ESRS reporting?

A shared dataset can support both frameworks, but reuse requires checks on materiality, boundaries, definitions and disclosure requirements. Retain separate assessment decisions and document any adjustments. The dedicated multi-framework section above explains the operational approach.

Scaling ISSB reporting is a data-control challenge before it is a reporting challenge. Groups that set shared methods, clear ownership and visible approvals now will handle new jurisdictions, new reliefs and assurance requests with far less rework.