# Why your biggest customers now expect you to report Scope 3 emissions Enterprise buyers are embedding Scope 3 emissions into procurement processes -shifting carbon reporting from optional to essential. This article explains why mid-market suppliers are now expected to calculate and disclose Scope 3 emissions, how those expectations show up in RFPs and onboarding platforms, and what data to prepare to remain in your customer’s vendor pool. It also outlines how software can help suppliers automate Scope 3 estimates, align with frameworks like the Science-Based Targets initiative (SBTi) and the Corporate Sustainability Reporting Directive (CSRD), and generate audit-ready outputs for procurement systems like SAP Ariba and EcoVadis Author: Anna Kuppel Published: 2026-01-02 Source: https://www.coolset.com/academy/why-your-biggest-customers-now-expect-you-to-report-scope-3-emissions ##### Key takeaways:

Scope 3 emissions are now a standard requirement in enterprise procurement, with buyers increasingly demanding transparent, supplier-level carbon data.
To stay in the vendor pool, suppliers must be ready with spend-based estimates, mapped emission factors, clear calculation methods, and alignment with frameworks like SBTi and CSRD.
Coolset supports suppliers by automating Scope 3 calculations from procurement data, generating audit-ready outputs, and integrating seamlessly with platforms like EcoVadis and SAP Ariba.

For mid-market companies, Scope 3 reporting has moved from an optional sustainability activity to a near-mandatory business requirement. Not because of direct regulatory obligation, but because your biggest enterprise customers — the ones who account for a disproportionate share of your revenue — are now required to report their own Scope 3 emissions. And Scope 3 Category 1 (Purchased Goods and Services) means your emissions become their emissions. This article explains the mechanics of why Scope 3 expectations are trickling down to mid-market suppliers, what the implications are, and how to prepare. ## Why enterprise customers are asking for your emissions data The EU’s Corporate Sustainability Reporting Directive (CSRD) requires large companies to disclose their full Scope 1, 2, and 3 greenhouse gas inventory — verified by an external auditor under limited assurance. For Wave 1 companies (already reporting), this is live. For Wave 2 companies (1,000+ employees and >€450M turnover), it’s coming in 2027. Scope 3 Category 1 — Purchased Goods and Services — covers emissions from everything a company buys. For most businesses, this is the largest single Scope 3 category, often representing more than 50% of total value chain emissions. To report it credibly, CSRD reporters need emissions data from their suppliers. That means you. ## What data your customers will ask for Enterprise customers reporting under CSRD will typically ask their suppliers to provide one or more of the following:

Scope 1 and 2 emissions for the products or services they purchase from you, often expressed per unit of revenue or physical output
Company-level GHG inventory aligned with the GHG Protocol, covering at minimum Scope 1 and 2
Methodology documentation to allow them to verify your numbers and include them in their own disclosure

Some customers will request this via formal procurement questionnaires or platforms like EcoVadis or CDP. Others will send direct data requests. The expectation is that this data will eventually be verified — either by your customer’s auditor or through your own third-party verification. ## The Coolset certification and audit trail Coolset’s carbon accounting methodology is certified by TÜV Rheinland, confirming it meets the GHG Protocol Corporate Standard and Scope 3 Standard. This means companies that calculate their emissions using Coolset can share their results with confidence that the methodology is independently certified — meeting the data quality expectations of CSRD reporters requiring supplier-level emissions data. ## How to prepare for Scope 3 data requests The most effective preparation is to build your emissions inventory now, before the requests arrive. Key steps:

Measure your Scope 1 and 2 emissions using a certified methodology aligned with the GHG Protocol. This is the foundation that all supplier data requests will assess.
Structure your measurement for sharing: make sure the data can be presented in a format your customers can use (e.g., per unit of product, per tonne of material delivered, or as a company-level total).
Document your methodology: customers requesting your data will want to know how it was calculated, what emission factors you used, and whether it has been verified.
Use the VSME as your disclosure framework: EFRAG’s Voluntary SME Standard is specifically designed for smaller companies providing sustainability data to CSRD reporters. Completing the VSME Basic Module gives you a structured, standardized disclosure that works for most customer requests.

## What this means for supplier relationships Scope 3 expectations are increasingly being embedded into procurement. Some companies are already moving beyond data requests to setting supplier decarbonization requirements: either reduce your emissions or provide evidence that you have a credible plan to do so. For mid-market companies, this creates both a challenge and an opportunity. Companies that can respond quickly and credibly to sustainability data requests will be more competitive in enterprise sales processes. Companies that can’t will increasingly face friction. For more on how to navigate this landscape, see our guide to the Omnibus proposal and its implications for supply chain reporting and our guide to CSRD audit readiness.