Guest post by: Chris Winchurch, General Manager, Novisto Carbon
Investors, lenders and customers are paying closer attention to Scope 3 emissions, and for good reason. For most companies, the value chain is where the bulk of their carbon footprint lies. A single Scope 3 total, however, says very little on its own. Without knowing how the figure was calculated, a reader has no way to judge how much weight it can bear.
That gap is wider than many realize. The EcoVadis and Kearney Carbon Action Report 2026 analyzed more than 56,000 companies. It found that only about 40% report Scope 3 emissions at all, and just 4% use primary supplier data to calculate them. Companies relying on lower-quality data may be underestimating their Scope 3 emissions by as much as three times. The challenge is not collecting more data. It’s understanding how reliable the existing data is.
What Scope 3 maturity looks like in practice
A mature Scope 3 program is not one with complete information. Few companies will ever reach that point, because most of the data sits with suppliers several steps removed from the reporting company. PwC’s 2026 State of Decarbonization research looked at 158 Fortune 500 companies. A quarter lacked any visibility beyond tier 1 suppliers, and only 18% consistently tracked supplier activities and emissions past that point.
Maturity is better measured by whether a company can explain its numbers. Can it say where the gaps are, how each figure was calculated and what has improved since the last cycle? Scope 3 maturity depends on transparency, not perfect data. An inventory with clearly explained gaps and limitations is more useful than a seemingly complete one that can’t be defended.
Know how much confidence each number deserves
Take a consumer electronics brand that relies on contract manufacturers, semiconductor suppliers, aluminum enclosures, lithium-ion batteries and air freight. Its Scope 3 inventory might combine supplier-reported figures, activity-based calculations and industry-average estimates. Each comes with a different level of reliability.
Supplier-specific data also requires scrutiny. A contract manufacturer might report emissions for only one of its facilities. It might leave out purchased electricity or allocate emissions across customers in a way that doesn’t match the buyer’s approach. Labeling every data point by source, and reviewing primary data for completeness and consistency, lets teams see how much of the inventory rests on solid evidence. Tracking the share of emissions calculated using data each type of data over time can also help measure progress.
Make methods and assumptions visible
The same purchase can produce very different emissions results depending on the calculation method used. The electronics brand could estimate the footprint of its aluminum enclosures based on dollars spent, from tons purchased or from a supplier-specific factor that reflects recycled content and the smelter’s power source.
Each method tells a different story. Under a spend-based approach, a 20% jump in aluminum prices would raise reported emissions even though nothing physical changed. Documenting the methods, emission factors and assumptions behind each category makes it easier to review and explain the results. This becomes important when the numbers start guiding supplier choices or reduction targets. Documentation also helps companies explain to stakeholders whether a year-over-year change reflects a real reduction or a change in methodology. Investors increasingly expect that distinction.
Focus improvement efforts where they matter
Not every data gap deserves the same attention. For the electronics brand, better information on semiconductors and batteries could materially change its reported footprint and its decarbonization priorities. Office supplies and business software can reasonably continue to rely on estimates for years.
Prioritizing this way keeps supplier engagement focused and requests manageable. It also points effort toward the information most likely to influence a disclosure or a decision. Clear ownership keeps that work on track. Teams should assign responsibility for supplier requests, for reviewing methods and evidence, and for deciding when an estimate should be replaced. They should also record what improved and what still needs work at the end of each cycle. That way the next inventory starts from what was learned, not from a blank page.
Credibility is the real goal
As Scope 3 figures appear in more disclosures, financing discussions and customer requirements, their credibility will matter as much as their size. A reported total that comes with a clear explanation of its data quality, methods and known gaps is far more useful than one that appears precise but can’t be explained. By documenting their methods and focusing improvements where they matter most, companies can give stakeholders greater confidence in the numbers they report.
About the author:
Chris Winchurch is General Manager of Novisto Carbon, leading strategy and execution for Novisto’s carbon management offering. He joined Novisto through its 2026 acquisition of Minimum, the enterprise carbon-accounting platform he founded, and previously worked as a consultant at Boston Consulting Group.
