How to Build an ISSB-Aligned Sustainability Report from Scratch in Singapore

What ISSB Alignment Actually Means

The International Sustainability Standards Board (ISSB) was established in 2021 as part of the IFRS Foundation, with a mandate to develop a single global baseline for sustainability disclosures that capital markets could rely on. In June 2023, the ISSB published its first two standards: IFRS S1 (General Requirements for Disclosure of Sustainability-related Financial Information) and IFRS S2 (Climate-related Disclosures). These two standards together define what it means for a sustainability report to be "ISSB-aligned."

IFRS S1 is the umbrella standard — it requires companies to disclose all material sustainability-related risks and opportunities, across environmental, social, and governance dimensions, using a framework that connects those risks to the company's financial position and prospects. IFRS S2 is the climate-specific standard. It applies the same four-pillar structure — Governance, Strategy, Risk Management, Metrics and Targets — exclusively to climate, and adds specific quantitative requirements around GHG emissions that S1 alone does not specify. For most Singapore companies, IFRS S2 is where the real work is, because it is what SGX has adopted as the mandatory baseline for climate disclosure.

"ISSB-aligned" therefore has a precise meaning: your report addresses all four pillars of IFRS S2 with the level of specificity the standard requires, your GHG metrics are calculated per the GHG Protocol (which IFRS S2 mandates as the calculation methodology), and the disclosures are structured so they can be compared across companies and verified by an external assurer. It is not a label you apply to any sustainability document — it is a structural and evidential standard. SGX has mandated IFRS S2-aligned disclosure from FY2025, with external limited assurance on Scope 1 and 2 figures required from FY2029. This guide shows how to build a report that meets that standard from the first year.

Pillar 1 — Governance

The Governance pillar requires you to describe how your board and management oversee climate-related risks and opportunities. This is the structural foundation of your report: before you can describe your strategy or your risk management approach, you need to establish who in the organisation is accountable for climate, and what mechanisms exist to ensure that accountability is exercised.

At the board level, IFRS S2 asks several specific questions. Does your board have a sustainability committee, or has it designated an existing committee (such as the Audit and Risk Committee) to oversee climate-related matters? Which individual director, or which committee, has ultimate accountability for climate risk? How frequently does the board receive climate-related information — is it a standing agenda item at every board meeting, or does it appear once a year in the context of the sustainability report? And what relevant skills and experience do board members have in relation to climate risk — engineering backgrounds, experience in carbon markets, formal ESG qualifications?

At the management level, the standard asks how management monitors, manages, and oversees climate-related risks and opportunities. This typically means describing which executive committee has climate as part of its remit, how management receives and reviews climate data, and how climate performance factors into management incentives or remuneration structures. If your CEO's bonus is partially tied to a carbon intensity target, that belongs in this section.

The governance section is largely narrative, but it must reflect your actual governance structure — not an aspirational one. External assurers and audit committees cross-check governance disclosures against board minutes, terms of reference, and organisational charts. If you describe a board sustainability committee that has not yet been formally constituted, that is a misstatement. Build the governance structure first, document it formally, then describe it in the report.

Pillar 2 — Strategy

The Strategy pillar is the most narrative-intensive section of an ISSB-aligned report. It requires you to describe the climate-related risks and opportunities that could reasonably be expected to affect your business model, strategy, and financial planning over short, medium, and long-term time horizons, and to explain how those factors actually influence your strategic decisions.

IFRS S2 distinguishes between two categories of climate risk. Physical risks are the direct impacts of climate change on your operations and assets: flooding of office or warehouse premises, heat stress affecting the productivity or health of outdoor workers, disruption to supply chains from climate events affecting your suppliers or the ports and logistics infrastructure you depend on. For Singapore, relevant physical risks include coastal flooding risk in low-lying industrial areas, the compounding heat stress on construction and logistics workers as average temperatures rise, and supply chain exposure to climate-vulnerable regions — Southeast Asian agricultural supply chains and manufacturing hubs in low-elevation coastal areas are particularly relevant.

Transition risks are the risks that arise from the shift to a lower-carbon economy. These include regulatory risks (Singapore's carbon tax, currently S$25 per tonne CO2e from 2024 and rising to S$45 per tonne in 2026, increases the direct operating cost of carbon-intensive activities), technology risks (the rapid cost decline of renewable energy and electric vehicles may obsolete assets or processes that assumed continued reliance on fossil fuels), and market and reputation risks (customers, investors, and lenders increasingly assess climate performance as part of their procurement and financing decisions).

The strategy section also requires climate scenario analysis — testing your business model against at least two climate scenarios: a scenario consistent with limiting warming to 1.5°C or 2°C (which tests transition risk, since the policy and technology changes required are significant) and a higher-warming scenario (which tests physical risk, since more warming means more physical climate impacts). Scenario analysis does not require precise quantitative modelling for most SMEs in FY2025 — a qualitative narrative that identifies the key sensitivities and explains the logic is acceptable as a starting point. But it needs to be genuinely analytical, not a generic description of climate change copied from a third-party report.

Pillar 3 — Risk Management

The Risk Management pillar moves from identifying climate risks (Strategy) to explaining how you manage them. IFRS S2 requires a description of your processes for identifying, assessing, prioritising, and monitoring climate-related risks, and — critically — how those processes are integrated with your overall enterprise risk management (ERM) framework. Climate risk cannot live in a sustainability document that the risk committee never sees; it needs to sit in the same risk register as financial, operational, legal, and reputational risks.

The practical starting point is a climate risk register. This is a document that lists the specific climate-related risks relevant to your business — the physical and transition risks you identified in the Strategy pillar — and for each risk records an assessment of likelihood (how probable is this risk over the relevant time horizon), potential financial impact (in ranges: low, medium, high, or actual dollar estimates where possible), the controls or mitigations in place, the residual risk level after controls, and the owner (who in the organisation is responsible for monitoring and managing this risk).

You also need to describe your risk assessment methodology. How did you determine which climate risks were material? What time horizons did you use for short, medium, and long-term? How did you assess likelihood — using historical data, scenario analysis, or expert judgment? What threshold of potential financial impact triggers inclusion in the risk register? Documenting the methodology matters because it allows a reader to evaluate whether your risk assessment is credible and whether risks that are not on your register were excluded for defensible reasons.

For most Singapore SMEs in FY2025, a basic climate risk matrix — a heat map showing risks plotted on a likelihood-versus-impact grid — combined with a risk register covering five to ten material risks is sufficient. The standard does not prescribe a format; it requires substance. As your programme matures, the risk management section should deepen to include quantified financial exposure estimates, integration with insurance and treasury risk frameworks, and board-level reporting on risk status.

Pillar 4 — Metrics and Targets

The Metrics and Targets pillar is the quantitative core of an ISSB-aligned report, and it is where most companies find the most complexity. IFRS S2 paragraph 29 specifies the cross-industry GHG metrics that every company must disclose, regardless of sector. Understanding each metric precisely is essential to producing disclosure that meets the standard.

IFRS S2.29(a) — Gross Scope 1 GHG emissions.Scope 1 covers all direct emissions from sources owned or controlled by the reporting entity. This includes fuel combustion in company-owned or leased vehicles, fuel combustion in on-site boilers, furnaces, or generators, industrial process emissions (relevant to manufacturing and processing companies), and fugitive emissions such as refrigerant losses from air conditioning and refrigeration equipment. "Gross" means before any carbon offsets or credits — the standard requires gross figures so that purchased offsets cannot be used to obscure the underlying emission footprint. The figure must be in tonnes of CO2 equivalent (tCO2e), using Global Warming Potential values from the IPCC assessment report specified in the standard.

IFRS S2.29(b) — Gross Scope 2 GHG emissions, both location-based and market-based.Scope 2 covers indirect emissions from purchased or acquired electricity, steam, heat, or cooling. For most Singapore companies, the dominant Scope 2 source is purchased electricity from the national grid. IFRS S2 requires both calculation methods to be disclosed: the location-based method uses the average grid emission factor published by Singapore's Energy Market Authority (EMA), reflecting the actual emissions intensity of electricity generation in Singapore; the market-based method uses the emission factor from your specific electricity contract or from renewable energy certificates (RECs) you have purchased. If you have purchased RECs or signed a power purchase agreement for clean energy, your market-based Scope 2 figure may be substantially lower than your location-based figure. Both must be disclosed, and the difference must be explained.

IFRS S2.29(c) — Scope 3 GHG emissions, when material or required.Scope 3 covers all other indirect emissions across the value chain — upstream (from purchased goods and services, capital goods, business travel, employee commuting, upstream transport and distribution) and downstream (from the use and end-of-life disposal of products). Under Singapore's SGX rules, Scope 3 disclosure is required on a best-efforts basis from FY2026. For FY2025 first-time reporters, the focus is establishing a credible Scope 1+2 baseline; Scope 3 can follow in FY2026 as the methodology and data collection develop.

IFRS S2.29(d) — Total GHG emissions. This is the sum of Scope 1 plus Scope 2 (and Scope 3 where applicable), expressed in tCO2e. It provides a single headline figure that allows comparison across years and across companies, and it is the number that appears in most benchmarking analyses and investor screens.

Beyond the GHG totals, IFRS S2 also requires an emission intensity metric — total GHG emissions normalised by a relevant business metric such as revenue (tCO2e per S$million of revenue), production output (tCO2e per tonne of product manufactured), or floor area (tCO2e per square metre of premises). Intensity metrics allow performance to be tracked even as the business grows, and they enable meaningful peer comparison. Finally, any climate-related targets the company has set — a carbon neutrality target, a Scope 2 renewable energy target, a supply chain emission reduction target — must be disclosed with a base year, a target year, and annual progress data.

The Evidence Chain: From Bill to Report Number

The single most important thing to understand about ISSB-aligned reporting is that every GHG metric must trace to source data. The number in your sustainability report is the end of a chain that starts with a physical document — a utility bill, a fuel invoice, a refrigerant recharge record — and passes through a documented calculation methodology before arriving at a tonnes of CO2 equivalent figure. An assurer's job in FY2029 is to walk that chain in reverse: from the reported number back to the source document. If any link is missing or cannot be verified, the assurance engagement fails.

For Scope 1, the source documents are: fuel purchase invoices or petrol card statements for company vehicles, fuel invoices for on-site generators or boilers, refrigerant recharge records (typically in a service log maintained by your air conditioning or refrigeration contractor), and for companies with industrial processes, process monitoring records or material balance data. Each document establishes an activity quantity — litres of diesel, kilograms of refrigerant charged — which is then multiplied by an emission factor to produce a tCO2e figure. The emission factor used must be documented: the source (IPCC AR6, Singapore NEA, or a manufacturer-specific factor), the specific value applied, and the date it was obtained. If you update an emission factor in a subsequent year, the change and its rationale must be documented as well.

For Scope 2, the primary source document is the SP Group electricity bill, which records monthly consumption in kilowatt-hours by meter. For companies with multiple sites, a separate bill and consumption figure is needed for each metered location. The location-based emission factor comes from EMA's published grid emission factor for Singapore, which is updated annually; the factor you apply must match the year of consumption, and the source (EMA publication, date, URL) must be recorded. If you are claiming a market-based Scope 2 figure lower than the location-based figure, you need to hold the contractual instrument that justifies the lower factor — the REC certificate, the power purchase agreement, or the relevant contract clause.

The evidence chain is not an abstract concept — it is a filing system. Every source document needs to be stored in its original form, linked to the calculation it supports, and preserved in a way that demonstrates it has not been altered since it was created. This is why an append-only, hash-chained evidence vault is the appropriate architecture: it means that neither you nor anyone else can modify a document after it has been filed, which gives an assurer immediate confidence that the evidence trail is intact. Building this system from day one — rather than reconstructing it from email attachments in 2028 — is the single most important decision you can make for FY2029 assurance readiness.

Formatting and Filing in Singapore

Once you have the four pillars written and the GHG metrics calculated, you need to assemble the report itself and understand the filing requirements. For SGX-listed companies, the sustainability report is a mandatory disclosure submitted to SGX as a separate filing, typically within four months of the financial year end — the same deadline that applies to the Annual Report. For companies with a 31 December financial year, this means the sustainability report for FY2025 must be filed by the end of April 2026. Companies with non-December financial year ends should check their specific deadline, which aligns with their Annual Report filing obligation.

The report may be structured in two ways. The most common approach is a standalone sustainability report — a separate PDF document covering only sustainability disclosures — which is filed to SGX separately from the Annual Report. Some companies choose to integrate sustainability disclosures into the Annual Report itself, in which case the relevant sections are clearly labelled and cross-referenced. Either approach is acceptable under SGX rules. The integrated approach is more common among larger listed companies with mature reporting programmes; standalone reports are more practical for first-time reporters because they allow the sustainability team to develop the content independently without coordinating the layout with the Annual Report production schedule.

In terms of length and depth, a first-time ISSB-aligned sustainability report for a Singapore listed company typically runs between 20 and 40 pages, including the four IFRS S2 pillars in narrative form, the GHG inventory tables, the methodology note, and any supplementary disclosures (targets, assurance statement if applicable, GRI or SASB index if the company chooses to cross-reference). Do not aim for length — aim for completeness and traceability. A concise 25-page report where every number links to a documented source is far more valuable than a 60-page report full of narrative that cannot be verified.

Non-listed companies are not required to file with SGX, but if you are producing a voluntary sustainability report, the most practical approach is to publish it on your website and reference it in your Annual Report or company profile. This makes it findable by clients, lenders, and partners who are requesting it for their own procurement or financing due diligence.

A Year-by-Year Improvement Roadmap

ISSB-aligned reporting is not a one-year project — it is a programme that builds capability and credibility over time. The companies that navigate FY2029 assurance successfully are the ones that treat each reporting cycle as an improvement sprint, not a compliance deadline. Here is a practical roadmap for a Singapore company starting from scratch.

Year 1 (FY2025): Build the foundation. The primary goal in the first year is to establish a credible, documented Scope 1 and Scope 2 baseline. This means: identifying all Scope 1 emission sources and ensuring the relevant source documents (fuel invoices, refrigerant records, vehicle logs) are being collected and stored; gathering full-year electricity consumption data from SP Group for all company sites; applying the GHG Protocol methodology with documented emission factors; and writing a methodology note that will be the reference point for all future years. The four-pillar narrative in the first year can be relatively brief — a genuine description of your current governance, strategy, and risk management practice, even if that practice is early-stage. Honest simplicity is better than elaborate claims that cannot be substantiated.

Year 2 (FY2026): Strengthen data quality and begin Scope 3. In the second year, the focus shifts to improving the accuracy and completeness of your Scope 1+2 data — identifying gaps from the first year, improving the coverage of emission sources, and documenting any restatements to the FY2025 baseline that better data requires. This is also the year to begin Scope 3 measurement, at least for the categories that are most material to your business: purchased goods and services for product companies, business travel for professional services firms, or upstream transport and distribution for retailers. The strategy section should deepen as you conduct your first formal climate scenario analysis, and the risk management section should reflect a more mature climate risk register.

Year 3 (FY2027): Integrate sustainability into financial planning.By the third year, your GHG data should be of sufficient quality and consistency to begin integrating climate considerations into financial planning processes — capital expenditure decisions, asset valuations, procurement policy, and product development roadmaps. The strategy pillar should be able to describe concrete examples of how climate risk has influenced specific business decisions. This is also the year to conduct an internal mock assurance review: have someone unfamiliar with your GHG data attempt to verify a sample of numbers against source documents, and identify any gaps in the evidence chain before an external assurer does.

Year 4 and beyond (preparing for FY2029 assurance): In the years leading up to FY2029, the priority is assurance readiness. Engage with an assurance provider early — ideally in FY2027 or FY2028 — to understand what they will require and to identify any methodological or documentation gaps. Ensure your evidence vault is complete and that every source document can be retrieved and linked to its corresponding GHG calculation without manual reconstruction. Consider whether you want to obtain limited assurance voluntarily for FY2027 or FY2028, which gives you the experience of a real assurance engagement before it becomes mandatory. From FY2029, limited assurance on Scope 1+2 disclosures is a regulatory requirement for SGX-listed companies — but for companies that have built their evidence chain carefully over four years, it should be a routine exercise rather than a crisis.