Supplier carbon questionnaires: how to answer customer requests without greenwash

A supplier carbon questionnaire is not just another form to fill in. It is a buyer trust test: can the supplier explain what it knows, what it has estimated, what it cannot prove yet and how the answer will improve?

This guide is for suppliers responding to buyer requests. Buyers should also read our Scope 3 supplier data collection guide.

Before answering

Do not start typing directly into the buyer portal. First, identify the reporting year, the legal entity being asked about, the sites and operations covered, the data sources available and the claims the company has already made publicly. Then decide which answers are measured, estimated or not yet available.

If the questionnaire asks for a parent company but the data only covers one office, say so. If it asks for product-level emissions but you only have company-level emissions, say so. Boundaries matter more than confidence.

The minimum viable answer pack

A small supplier does not need a glossy sustainability report to answer better. It needs a minimum viable answer pack: the smallest set of evidence that lets the buyer understand the boundary, method, limits and next improvement.

The aim is not to look bigger or more advanced than the business really is. It is to give the buyer a consistent answer that can be checked, improved and reused.

What the buyer is really asking

The visible question may be "what are your emissions?" The underlying question is usually sharper: can this supplier support the buyer's Scope 3 reporting, procurement risk review or public sustainability claim without creating a weak link in the evidence chain?

That is why short, clear answers often beat long sustainability narratives. A buyer can work with partial data if the boundary, method and improvement plan are visible. It is much harder to use a polished answer that hides uncertainty.

Buyer question to evidence map

Most supplier questionnaires collapse several buyer needs into short portal questions. Treat each question as a request for evidence, not as an invitation to write a sustainability essay.

How to answer common questions

Sample answer wording

If you have measured emissions: "We have calculated Scope 1 and Scope 2 emissions for the 2025 reporting year using UK government conversion factors. Our current Scope 3 estimate covers business travel and employee commuting. Purchased goods data is being reviewed and will be improved in the next reporting cycle."

If you have not measured yet: "We have not yet completed a full greenhouse gas inventory. We can provide energy, travel, fuel and spend data to support your supplier assessment, and we intend to create a first baseline during the next reporting period."

If asked for a net-zero target: "We have not published a net-zero target yet because our Scope 3 baseline is incomplete. Our current priority is to establish a measured baseline and identify reduction actions before publishing a target."

Try it: convert a supplier activity figure

Some questionnaires ask for activity data rather than a finished carbon footprint. A small converter is useful when a buyer asks for the emissions impact of fuel, energy, travel or another activity type and the supplier needs to understand the order of magnitude before responding.

Tool via The Carbon Workbench. Use as a planning estimate, not a verified supplier disclosure.

When you do not know the answer yet

It is acceptable to say that a value is estimated or not yet available, as long as the response is clear. Many buyers prefer transparent partial data to confident but unsupported claims. Give a timeline for improvement where possible.

Evidence to attach

• Carbon footprint summary.
• Calculation methodology and emission factors.
• Energy, fuel, travel and logistics records.
• Carbon reduction plan.
• Environmental policy or management system documents.
• Evidence for renewable energy or lower-carbon procurement claims.

Red flag claims

• "We are carbon neutral" without explaining emissions boundary, reductions, offsets and retirement evidence.
• "All our products are sustainable" without product-level evidence.
• "We use renewable energy" without contract, certificate or tariff evidence.
• "We will be net zero by 2030" without baseline, scopes, actions and governance.

When to escalate internally

Escalate before submitting if the questionnaire asks for legal commitments, public claims, net-zero targets, product carbon footprints, offsets, renewable energy claims or assurance statements. These answers can create commercial and legal risk if they are not checked by the right people.

Answer library

Suppliers that receive repeated questionnaires should build an approved answer library. It should include the latest emissions figures, reporting boundary, reduction actions, evidence links, target wording and approved caveats. Each answer should have an owner and review date. This avoids teams giving inconsistent answers to different buyers.

What buyers usually want to know

Most buyer questions are trying to answer a few underlying concerns: does the supplier understand its emissions, can the supplier support the buyer's Scope 3 reporting, is there a credible reduction plan, and is there greenwashing risk? If your answer addresses those concerns clearly, it will usually be stronger than a long but vague sustainability statement.

What to do after submitting

Save a copy of the questionnaire, evidence files and submitted wording. If the buyer asks follow-up questions, add those answers to the internal answer library. Over time, this creates a stronger carbon response pack and reduces the workload for future tenders.

Also record questions the business could not answer. Those unanswered questions are a useful roadmap for the next carbon accounting cycle.

Read next

If the questionnaire exposes weak data, use the guide to Scope 3 emissions for SMEs and the carbon reduction plan template. If the buyer is asking because of wider procurement rules, read net-zero procurement requirements. If the concern is greenwashing, use the green claims checklist before submitting public wording.

The pattern is usually the same: answer the immediate request, save the evidence, then turn repeated buyer questions into a more stable carbon reporting process.

How to handle scoring portals

Some portals force suppliers into yes or no answers even when the true answer is more nuanced. Where possible, use the comment box to explain the boundary and improvement plan. If there is no comment box, keep a copy of the limitation internally and consider sending clarification through the buyer's question process.

Do not let a rigid portal push the business into an inaccurate claim. A "no, but here is our current plan" answer may be less glamorous, but it is safer than saying yes to a target, assurance statement or product footprint that does not exist.

FAQ

Should a supplier answer "yes" if it plans to measure emissions soon?

No. If emissions are not measured yet, say that. Then explain what data is available and when a first baseline is expected.

Should a supplier mention offsets?

Only if offsets are relevant, documented and retired properly. Do not use offsets to avoid answering questions about gross emissions and reduction actions.

What if the buyer asks for product carbon data?

If product data is not available, explain what alternative data can be provided, such as product weight, materials, units sold, energy use or supplier information. Do not invent a product footprint.

Useful sources

• GOV.UK: carbon reduction plans and procurement
• GHG Protocol: Corporate Standard
• GHG Protocol: Scope 3 Standard
• EFRAG: Voluntary reporting standard for SMEs project page
• UK Green Claims Code