STI constituents must report Scope 3 emissions in 2027. The burden mostly falls on unlisted firms

SINGAPORE’s largest listed companies are in their first financial year of mandatory Scope 3 reporting.

Under the timeline set by the Accounting and Corporate Regulatory Authority and Singapore Exchange (SGX) Regulation, Straits Times Index constituents must report Scope 3 greenhouse-gas emissions for financial years beginning on or after Jan 1, 2026.

So the numbers are being assembled now, for reporting in 2027. Officially, only the STI’s 30 constituents must report these figures. In practice, that obligation cascades down the supply chain – companies with no disclosure duty of their own, listed or not, will find themselves pulled into this chain.

That is because Scope 3 covers emissions a company does not directly control: 15 categories under the Greenhouse Gas Protocol – a standard for measuring emissions – of which purchased goods and services is typically the largest.

For a manufacturer, a builder, a retailer, or a bank, the bulk of the footprint sits with suppliers.

Hence, while the obligation falls on the index’s 30 constituents, the actual measurement falls on the thousands of unlisted firms that sell to them.

An estimation for an obligation

That asymmetry is the real shape of Singapore’s Scope 3 year.

Consider what buyers ask of suppliers for Scope 3 accounting. Each supplier must build an inventory from scratch: 12 months of electricity bills, fuel receipts, vehicle logs, refrigerant top-ups, waste disposal volume.

Each activity figure is then multiplied by the relevant emission factor, such as Singapore’s grid factor for electricity or fuel-specific factors for diesel. This raises another question: Which factor set should be used, and from which year?

This problem is compounded by the sheer number of suppliers that a buyer needs this data from.

Where primary data described in the above scenario is missing, buyers fall back on spend-based approximations. That is, they multiply what was paid to the supplier by an industry average figure, such as the estimated volume of carbon dioxide per dollar spent on transport.

This produces a number – which is what the reporting regulation demands – but it cannot fall when the supplier decarbonises. Cut diesel use by a third, and the estimate does not move.

Buyers end up reporting figures insensitive to the very behaviour disclosure was meant to encourage.

The way out is procedural as well as technological. One inventory, built once at the supplier from primary activity data, mapped to a recognised standard framework, and reissued rather than rebuilt each time a buyer requests emissions information.

This solves one of sustainability reporting’s most stubborn problems: capturing fragmented, unstructured data at scale.

Take a typical life cycle of a Green Mark-certified building owned by a large developer listed on the SGX.

The construction contractor buys materials and fuel from dozens of suppliers – concrete by volume, glass and steel in varying dimensions and diesel by the litre.

Each must be converted into weight and matched to the right emissions factor, month after month, for the duration of construction, just to arrive at one embodied carbon figure.

Done manually, this is slow, error-prone and overwhelming for most firms.

But digital tools now available can automate much of this: extracting data directly from the different materials delivery orders and invoices, then applying the correct conversions against weight-based emissions factors from the Singapore Emissions Factors Registry.

What was once a laborious, inconsistent exercise becomes a reliable, repeatable process, one that can feed directly into the Scope 3 calculations developers increasingly must report.

Data disclosure drives business

Findings from our own client base of over 800 Singapore companies show what happens when suppliers are enabled to produce this data themselves.

Firms that moved to digital tracking and reporting are winning up to 15 per cent more tenders with high-quality evidence-backed disclosures.

They are slashing operational costs by two-thirds by identifying optimisation opportunities and catching wastage or equipment leakages during the carbon accounting process.

Finally, they are also cutting greenhouse-gas emissions by as much as 88 per cent, by identifying hotspots and targeting high-impact decarbonisation initiatives such as electrification and renewable energy.

Notably, these statistics are drawn from small and medium-sized enterprises (SMEs), not listed corporates.

The data tells a clear story: SMEs disclosing voluntarily ahead of any mandatory requirement get tangible business wins. That is the real test of a good rule: It drives the right behaviour even among organisations it does not legally bind.

At the same time, buyers now have something better to ask against than a bespoke spreadsheet.

Technical Reference 149:2026, published in May 2026 by Enterprise Singapore through the Singapore Standards Council, sets out four sustainability maturity levels – Essential, Bronze, Silver and Gold – across five dimensions, including operations and supply network.

A supplier’s maturity level tells a buyer that the numbers it provides were measured, not assumed.

The public sector intends to include sustainability criteria in all eligible tenders by 2028, so the question for buyers is no longer if their suppliers design for the process, but how.

None of this needs a new rule. The one that exists was written for 30 companies. The work it created belongs to firms it never mentions, and the impact reaches far beyond what the headline lets on.

What happens next depends on adoption: of the standards and the tools that make them usable.

The writer is founder of ESGpedia