Scope 3 emissions — the indirect greenhouse gas (GHG) emissions that occur across a company's value chain, from purchased goods and services to product use and disposal — account for around 75% of a typical organization's total carbon footprint, according to EcoVadis's 2026 Scope 3 reporting analysis. They are also the hardest emissions to measure, because measuring them depends on data from other organizations. As Scope 3 disclosure becomes a legal obligation under the EU's Corporate Sustainability Reporting Directive (CSRD), California's SB 253, and Australia's mandatory climate framework, the quality of that supplier data is no longer just a sustainability reporting concern. It is a compliance infrastructure problem.
The numbers describing the current state are difficult to look at optimistically. EcoVadis and an IBM-commissioned survey found that only 38% of businesses are currently measuring their Scope 3 footprint. Tier 1 supplier visibility reaches 95% of companies — but that visibility extends to Tier 2 or beyond for only 42%. A separate finding from the same research: Scope 3 supply chain emissions are on average 26 times greater than a company's direct operational emissions. The gap between what regulation requires and what supply chains can currently deliver is not narrow.
Why Supplier Data Is Structurally Difficult to Get Right
The fundamental challenge in Scope 3 data collection is not that suppliers are unwilling to share information. Many are. The problem is that most suppliers — particularly small and mid-size manufacturers, logistics providers, and agricultural producers — do not have the internal systems to produce emissions data in the format, at the granularity, and with the documentation trail that an independent auditor would accept. IPOINT Systems' CSRD Scope 3 analysis puts it plainly: data quality suffers from supply-chain complexity, with thousands of suppliers, limited primary data, and varying calculation methods. Reliance on averages and estimates increases uncertainty and raises the bar for verification.
The MIT State of Supply Chain Sustainability Report identified a lack of standardized methodologies as a challenge for 53% of companies, followed by complexity of calculations (52%), limited internal expertise or resources (39%), and the high cost of measurement tools (32%). Spreadsheets remain the top data collection tool across most supply chains — which means the "data" arriving from suppliers is often a series of manual estimates compiled in Excel by someone who was not trained in GHG accounting and may not know which emission factor to use.
The Audit Readiness Problem That Is Building Downstream
For companies with CSRD obligations or California disclosure requirements, Scope 3 data that arrived as a supplier questionnaire response and was cleaned up before submission is not audit-ready. An auditor examining a Scope 3 inventory will ask for the underlying source data behind each category — the activity data, the emission factors, the calculation methodology, and the documentation showing those choices were applied consistently. Rebalance Impact's GHG Protocol 2026 update analysis frames the question directly: can your infrastructure withstand a 95% completeness audit, or are there blind spots in your supply chain?
For suppliers, the stakes have shifted. Failing to provide granular, evidence-backed emissions data now risks the loss of contracts and market share as buyers build their Scope 3 reporting obligations into sourcing criteria. A supplier without reliable emissions data is a liability for any buyer who needs auditable Scope 3 figures. The pressure is moving down the supply chain faster than most Tier 2 and Tier 3 suppliers have recognized.
What Procurement Leaders Need to Own That Sustainability Teams Cannot
The biggest structural mistake in Scope 3 programs is treating supplier data collection as a sustainability team task. As EcoVadis notes, accurate Scope 3 data sits inside supplier operations, logistics networks, and procurement systems. The people who manage those relationships are in procurement, not sustainability. Getting primary emissions data from suppliers requires the kind of contract leverage, relationship capital, and operational access that procurement teams hold and sustainability teams typically do not.
Companies that have built their Scope 3 programs around annual questionnaires sent to Tier 1 suppliers are producing figures that may satisfy today's voluntary reporting norms. They are not producing figures that will satisfy the assurance requirements embedded in CSRD, SB 253, or Australia's mandatory climate disclosure rules. Building the supplier engagement infrastructure that can close that gap takes longer than a single reporting cycle. Procurement teams that are not already working on it are behind the timeline that mandatory disclosure creates.
