What to Do When Customer Sends Scope 3 Questionnaire
The email subject line mentions "Scope 3" and suddenly you're searching for what that even means. Your customer needs carbon data from their supply chain, and you're part of that chain. The questionnaire asks about emissions categories you've never heard of, activity data you've never tracked, and methodologies you couldn't explain if your business depended on it.
Which, increasingly, it might.
Scope 3 requests are becoming standard for suppliers to large companies. Here's what's actually being asked, what you realistically can provide, and how to respond professionally even if carbon accounting is completely new to you.
What Scope 3 Actually Means
Carbon emissions are categorized into three "scopes":
Scope 1 covers direct emissions from sources your company owns or controls. If you have vehicles, boilers, or manufacturing equipment that burns fuel on-site, those emissions are Scope 1.
Scope 2 covers indirect emissions from purchased electricity, heating, or cooling. When you pay your electric bill, the emissions from generating that power count as your Scope 2.
Scope 3 is everything else in the value chain—both upstream (your suppliers, business travel, employee commuting, purchased goods) and downstream (product use, end-of-life treatment, transportation to customers).
Here's why this matters for you: when your customer reports their emissions, your operations fall into their Scope 3. The products or services you provide them? Those emissions show up in their "purchased goods and services" category. They can't complete their carbon report without data from suppliers like you.
Why This Request Is Different from General ESG
A general ESG questionnaire asks about many topics—environment, social practices, governance. Scope 3 requests focus specifically on carbon: how much greenhouse gas is associated with what you provide to this customer.
This specificity is both harder and easier than general ESG. Harder because you need actual numbers, not just policy statements. Easier because the scope is narrower—you're not being asked about human rights policies or board diversity in a Scope 3 questionnaire.
What customers typically want:
Total emissions in CO2 equivalent (CO2e). This is the headline number. How many tonnes of carbon dioxide equivalent are associated with the products/services you provide them?
Breakdown by scope. Some customers want to see your own Scope 1, 2, and 3 separately so they understand where your emissions come from.
Activity data. Even if you can't calculate emissions yourself, they may accept raw data: energy consumption in kWh, fuel usage in liters, material quantities in kg. They can apply emission factors themselves.
Methodology explanation. How did you calculate these numbers? What's included and excluded? What assumptions did you make?
Year-over-year comparison. If you've been tracking, they want to see trends.
The Honest Starting Point
If you've never tracked carbon emissions, acknowledge that upfront—to yourself and eventually to your customer. You're not going to produce perfect GHG Protocol-compliant data in the two weeks before their deadline. But you can provide something useful.
Start with what you know:
Energy bills. Your electricity and gas consumption is documented monthly. This is your Scope 2 (electricity) and Scope 1 (gas, if used for heating or processes).
Fuel purchases. Vehicle fuel, heating oil, any combustion you control on-site. This is Scope 1.
Basic production data. How much product did you produce? What materials went into it? This helps calculate intensity metrics (emissions per unit produced).
With just these inputs, you can provide a reasonable first estimate of your Scope 1 and 2 emissions. Scope 3 for your own operations (your supply chain's emissions) is more complex and many suppliers reasonably exclude it in early reporting stages.
Calculating Your Numbers
The basic formula for carbon emissions is: Activity Data × Emission Factor = Emissions
Activity data is what you did: consumed 50,000 kWh of electricity, burned 10,000 liters of diesel.
Emission factors convert activity into carbon: electricity in Germany averages about 0.4 kg CO2e per kWh; diesel emits about 2.7 kg CO2e per liter.
Government agencies and organizations publish emission factor databases. The UK's DEFRA conversion factors are widely used and freely available. Your country's environment agency likely publishes national grid emission factors.
For a basic calculation:
- Gather 12 months of energy bills
- Sum up consumption by type (electricity, natural gas, vehicle fuel)
- Apply standard emission factors
- Sum the results
This gives you Scope 1 and 2 with reasonable accuracy. It won't satisfy an auditor demanding GHG Protocol Category 15 Sub-clause B precision, but it answers your customer's core question: approximately how much carbon is associated with your operations?
What If You Can't Calculate Full Emissions?
This is normal. The article on responding when you don't have everything covers strategies, but specifically for Scope 3 requests:
Provide activity data and let them calculate. Send your kWh consumed, liters of fuel used, tonnes of materials purchased. Sophisticated customers have systems to apply their own emission factors.
Use industry averages as proxies. If you manufactured 500 tonnes of steel components, published emission factors for steel production can provide estimates. Flag these as estimates, not measured values.
Calculate what you can, acknowledge what you can't. "We have measured our Scope 1 and 2 emissions. Scope 3 calculations are in development and we expect to report these from Q3 2025." This is honest and shows a path forward.
Ask what they actually need. Some customers have specific categories they care about. If they mainly need product-level carbon intensity, focus your effort there rather than calculating comprehensive organizational emissions.
Structuring Your Response
A clear Scope 3 response includes:
Reporting period. What 12-month period does this cover?
Organizational boundary. What's included? All facilities? Just the one that supplies this customer?
Emission sources. What categories are covered (Scope 1, 2, 3)? What's excluded and why?
Methodology. What approach did you use? What emission factors? What assumptions?
The numbers. Total emissions, broken down by scope and significant categories.
Data quality notes. What's measured versus estimated? What gaps exist?
Improvement plans. What will be better next time?
Customers receiving hundreds of supplier responses appreciate this structure. It's scannable, the methodology is transparent, and gaps are acknowledged rather than hidden.
Common Scope 3 Response Mistakes
Providing percentages without absolute numbers. "We reduced emissions 10%" means nothing without knowing 10% of what. Customers need tonnes CO2e.
Mixing up scopes. Your Scope 2 (purchased electricity) is not the same as your customer's Scope 3 from you. Understand what you're reporting.
Using outdated emission factors. Grid electricity gets cleaner over time. Using 2015 emission factors for 2024 electricity overstates your impact. Use current factors.
Over-engineering the response. A clear spreadsheet with documented methodology beats a 50-page report that buries the actual numbers. Lead with data.
Ignoring the customer's format. If they sent a template, use it. Don't make them extract your numbers from a narrative document.
Building Ongoing Capability
Scope 3 requests will recur. Every customer subject to CSRD will ask annually, and more customers fall under these regulations each year. Responding once is a project; responding annually needs a system.
The ESG response checklist outlines what to track. At minimum:
- Monthly energy consumption by type
- Fuel purchases for company vehicles
- Major material inputs by weight
- Production volumes for intensity calculations
With these tracked continuously, annual Scope 3 responses become a few hours of compilation rather than weeks of archaeology through old invoices.
The Competitive Reality
Suppliers who can provide carbon data have an advantage. Not because customers prefer environmentally superior suppliers (though some do), but because they make their customers' compliance easier.
When a procurement team is choosing between two similar suppliers, one who provides clean carbon data and one who doesn't respond to Scope 3 requests, the choice is straightforward. The compliant supplier reduces workload; the non-compliant supplier creates it.
You don't need the lowest carbon footprint. You need a credible number, clearly documented, delivered on time. That's the bar. Many of your competitors won't clear it.
Need a system for this? ESG Passport lets you track ESG data year-round and respond to any questionnaire in hours — not weeks. Free ESG tracking for life. Pro turns your data into finished reports with 200+ automated answer templates.