Why would a buyer ask only its biggest suppliers for emissions data, and is 80 percent of spend a rule in the Greenhouse Gas (GHG) Protocol?

No. 80 percent of spend is an example, not a rule. The Scope 3 Standard's example ranks tier 1 suppliers by spend, picks the largest until they reach 80 percent, then adds any supplier above 1 percent of spend or relevant for other reasons. Companies may set their own threshold.

The steps in the standard's example

1. Get a complete list of total spend by supplier.
2. Rank tier 1 suppliers by their share of total spend.
3. Select the largest tier 1 suppliers that together account for at least 80 percent of spend.
4. Within the remaining 20 percent, select any supplier individually above 1 percent of spend, or relevant for other reasons.

Why tier 1 first

The standard says to engage tier 1 suppliers first. These are companies the buyer has a purchase order with. They have contractual obligations to the buyer, which gives the leverage needed to ask for GHG inventory data. Tier 2 suppliers, the ones a tier 1 supplier buys from, come later and only where relevant.

Eighty percent is not fixed

A footnote says it plainly: eighty percent is an example threshold, companies may define their own, and the percentage can be increased over time as the buyer and its suppliers gain experience.

Other reasons a supplier gets picked

• The standard's examples: contract manufacturers, suppliers expected to have significant emissions, suppliers that produce or emit hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) or sulphur hexafluoride (SF6), suppliers of high-emitting materials, and suppliers in priority spend categories the company defines.
• Where there are many suppliers, it says to target the most relevant by spend and/or expected emissions impact, and those where the buyer has more influence, such as contract manufacturers or suppliers for whom the buyer is a significant share of sales.
• For suppliers not asked, or whose data is incomplete, the buyer uses secondary data.

If you are a small supplier

My reading, not the standard's: being under the cut today does not mean you are never asked. The share can rise, a buyer can add a material it thinks is high-emitting, and a buyer that depends on you for a product may treat you as relevant whatever your spend.

A buyer with 1,000 lakh rupees (Rs) of tier 1 spend

• Ranked by spend in Rs lakh: S1 300, S2 220, S3 140, S4 90, S5 60. After S4 the total is 750, which is 75%, so S5 is needed: 750 + 60 = 810, which is 81%
• Remaining Rs 190 lakh (19%). Suppliers above 1% (Rs 10 lakh) join: S6 40, S7 30, S8 25, S9 20, S10 15, S11 12, a total of 142
• Left out: 190 minus 142 = Rs 48 lakh (4.8%), spread across smaller suppliers each under Rs 10 lakh. Their emissions are estimated with secondary data
• Asked for data: 11 suppliers covering 810 + 142 = Rs 952 lakh, which is 95.2% of spend

Example numbers, not from the standard. The standard's own figure picks suppliers A to I to reach 80 percent and adds J because it is individually above 1 percent.

What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records. If a buyer asks you for plant figures, those monthly records are the activity data behind your answer.

• Which suppliers to engage first on Scope 3
• Supplier details a buyer needs for Scope 3 engagement
• Collecting data from your own suppliers
• Small suppliers and CDP value chain requests
• Buyer sends its own questionnaire format

Sources: GHG Protocol Corporate Value Chain (Scope 3) Accounting and Reporting Standard, chapter 7 (section 7.4, Boxes 7.3 and 7.5, Table 7.8, footnote 8)

Last reviewed 2026-11-05. Wording is from the 2011 Scope 3 Standard. A buyer's own supplier policy decides who is asked; ask the buyer for its selection rule if it matters to you.