Scope 3: using supplier-specific data

What counts as supplier-specific data?

The GHG Protocol's Scope 3 Standard and its technical guidance describe two supplier-based methods for purchased goods and services. The supplier-specific method uses product-level cradle-to-gate emissions provided by the supplier, covering everything up to the point the product leaves the supplier's gate. The hybrid method combines supplier data where available, such as the supplier's scope 1 and 2 emissions allocated to the products bought, with secondary data for the rest, such as the materials the supplier buys and their transport. See the spend-based method and scope 3 category 1.

How should a supplier's emissions be allocated?

When a supplier gives its whole-company inventory rather than product footprints, the company's share must be allocated. Physical allocation, such as by tonnes, units or machine hours, best reflects how emissions arise and is preferred; economic allocation by revenue is simpler but moves with prices. The allocation should cover the same period as the purchases and exclude emissions from products the company does not buy where possible. Any allocation method should be applied consistently and disclosed.

Supplier-specific data: one supplier, three methods

A company buys US$ 40 million of machined components, 4,000 units, from a supplier with revenue of US$ 1,000 million and scope 1 and 2 emissions of 60,000 tonnes.

The spend-based estimate, using an industry average factor, is 6,000 tonnes. Under the hybrid method, the supplier's scope 1 and 2 are allocated by revenue, 40/1,000 of 60,000 = 2,400 tonnes, plus 1,500 tonnes of secondary estimates for the steel and coatings the supplier buys, giving 3,900 tonnes. The supplier then provides a product carbon footprint of 0.9 tonnes per unit, verified by a third party, giving 3,600 tonnes. The footprint is lowest because the supplier's plant runs on renewable electricity, which the industry average does not reflect. The company uses the footprint and records the data quality. See market-based scope 2.

How is supplier data quality judged?

Companies check that the boundary is cradle-to-gate and complete, that the period matches, that the method follows a recognised standard, that the share of primary data in the footprint is known, and whether a third party has verified it. Supplier footprints that use market-based electricity claims should state so. Poor-quality supplier data can be worse than a good average, so many companies score data quality and use supplier figures only above a minimum. See choosing emission factors.

How do companies collect supplier data at scale?

Most start with the suppliers behind most of their category 1 emissions, often a few dozen, and ask for product footprints or allocated inventories through standard questionnaires or platforms such as the CDP supply chain programme. The WBCSD's PACT methodology and technical specifications, updated to version 3 in 2025, give a common way to calculate and exchange cradle-to-gate footprints between systems. Under the EU's value chain cap, suppliers with 1,000 employees or fewer cannot be required to provide more than set datapoints for CSRD reporting, but many share footprints voluntarily. See the value chain cap.

What should be disclosed about supplier-specific data?

IFRS S2's measurement framework prefers primary data from the value chain and asks companies to explain their scope 3 inputs and assumptions. ESRS E1 asks for the share of scope 3 calculated using primary data from suppliers or other value chain partners. CARB's proposals for SB 253 would require the percentage of scope 3 based on primary supplier data. Companies should report the share, the methods and the main data gaps, and explain changes as supplier data replaces estimates. See SB 253 scope 3 from 2027.

This guide is general information. It is not tax or legal advice for your situation.