Short answer: if a customer has asked your company for GHG or emissions data, do not start by filling in numbers. Start by reading the request and turning it into a checklist: what period is covered, which business boundary applies, which scopes are requested, whether any service-level allocation is needed, what evidence is expected, and who will review the response before it goes back to the customer.
The goal is not just to produce a number. The goal is to create a customer-ready response with calculations, assumptions, data sources, and a file you can reuse the next time the same customer asks.
Supplier GHG requests often arrive in a slightly awkward way. A procurement contact forwards a portal email. An account manager says the customer needs emissions data by the end of the month. Finance, operations, HR, logistics, and facilities are suddenly asked for energy bills, travel data, fuel records, or spend reports.
At that point, the biggest risk is not that the company has no data. It is that the team starts collecting the wrong data before it understands the request. A customer may be asking for a company footprint, a product or service-level number, a CDP or EcoVadis-style questionnaire response, a consultant letter, independent assurance, or just enough evidence to support a procurement file. Those are different jobs.
Use this checklist to slow the work down for half an hour before you speed it up.
First, read the customer request carefully
Before asking anyone for invoices or spreadsheets, copy the exact wording of the request into your working file. Preserve the original email, portal instructions, template, deadline, and any attachments. If the customer has named a standard, reporting portal, assurance requirement, or emissions scope, keep the wording intact.
Look for these details first:
- The customer, platform, or procurement team making the request.
- The deadline and whether there is a clarification window.
- The reporting period, such as calendar year, financial year, or a customer-specific period.
- The boundary: whole company, specific legal entity, site, contract, product, or service line.
- The requested emissions scopes: Scope 1, Scope 2, relevant Scope 3, product carbon footprint, or service-level emissions.
- The format: customer template, supplier portal, questionnaire, spreadsheet, letter, or report.
- Any language around assurance, verification, validation, consultant support, or supporting documentation.
This matters because a supplier response can become messy when the team treats every request like a full ESG report. Many customer requests are narrower than that. Some are broader. The wording tells you which one you have.
The supplier GHG reporting checklist
1. Request and deadline
- Save the original request, template, portal screenshots, and attachments.
- Record the deadline, customer contact, and internal owner.
- List any mandatory fields, optional fields, and places where the customer allows explanation.
- Check whether the customer is asking for numbers only, numbers plus methodology, or a full supporting evidence pack.
2. Boundary and reporting period
- Confirm the reporting period before collecting data.
- Decide whether the response covers the whole company, one entity, one site, one customer contract, or one service line.
- Note any exclusions clearly, especially if an office, country, subsidiary, or outsourced operation is not covered.
- Keep the boundary consistent across Scope 1, Scope 2, and Scope 3 unless the request says otherwise.
3. Scope 1 data
- Collect fuel use for owned or controlled vehicles, generators, boilers, or other combustion sources.
- Collect refrigerant top-ups or leakage records where air conditioning, refrigeration, or cooling equipment is material.
- Collect process emissions only if they apply to your operations.
- Record units, dates, sites, and evidence sources for every activity data point.
4. Scope 2 data
- Collect electricity invoices, meter data, landlord statements, or utility summaries.
- Include purchased steam, heat, or cooling if relevant.
- Separate data by site or country if emission factors differ.
- Keep evidence for renewable electricity claims, contracts, energy attribute certificates, or green tariff information.
5. Relevant Scope 3 screening
- Check which Scope 3 categories are relevant to the request, not just which categories are easiest to calculate.
- For many suppliers, this may include purchased goods and services, capital goods, fuel and energy-related activities, transport and distribution, waste, business travel, employee commuting, and leased assets.
- Collect spend, activity, distance, weight, supplier, or travel data depending on the category.
- Mark categories as calculated, estimated, not applicable, or not requested, with a short reason.
6. Service-level or customer-specific accounting
- Check whether the customer wants emissions for your company overall or for the specific service you provide to them.
- If service-level accounting is needed, define the allocation driver before calculating: revenue, headcount, hours, tickets, transactions, square meters, usage, contract volume, or another operational metric.
- Document why the allocation method is reasonable and where the data came from.
- Do not mix a company-wide footprint with a service-level response without explaining the difference.
7. Calculation method and emission factors
- Record the standard or methodology used, usually starting from the GHG Protocol where appropriate.
- Record emission factor source, geography, year, and units.
- Keep a clear trail from source data to emissions result.
- Flag any estimates, proxy data, or assumptions that the customer may need to understand.
8. Evidence pack
- Save energy bills, fuel records, travel exports, waste reports, logistics data, and source spreadsheets.
- Keep a methodology note that explains boundary, scopes, emission factors, assumptions, exclusions, and limitations.
- Keep a copy of the final customer submission.
- Keep one clean folder structure so the file can be refreshed next year.
9. Review before submission
- Check that totals match the requested unit and period.
- Check that the response does not overstate assurance, verification, renewable energy, or reduction claims.
- Check whether the customer asked for a consultant letter or independent assurance. These are not the same thing.
- Have one person review the numbers and another person review the wording before submission.
What data suppliers usually need
For a basic supplier GHG response, the most common data set starts with Scope 1 and Scope 2. Scope 1 usually means fuel, fleet, refrigerants, and any direct operational emissions under the company boundary. Scope 2 usually means purchased electricity and, where relevant, purchased heat, steam, or cooling.
Scope 3 is where supplier requests vary more. Some customers ask for only a limited set of upstream categories. Others ask for relevant Scope 3 categories or service-level emissions connected to the work you do for them. If the request mentions Scope 3 but does not explain which categories matter, treat that as a clarification point rather than guessing silently.
The GHG Protocol Corporate Standard is a common starting point for company inventories. The GHG Protocol Scope 2 Guidance is especially relevant when electricity contracts, renewable energy certificates, or market-based claims are involved. The GHG Protocol Scope 3 Standard is useful when the customer request reaches beyond your direct operations into value-chain emissions.
What usually goes wrong
The most common mistake is treating the customer request like a generic sustainability project. That makes the work bigger than it needs to be, and it can still miss the specific thing the customer asked for.
- Starting with calculations before reading the request. You may calculate a company footprint when the customer needs service-level emissions, or the other way around.
- Submitting numbers without methodology. A total without boundary, period, factors, and assumptions is hard for a customer to trust.
- Ignoring Scope 3 because the data is imperfect. Many Scope 3 responses start with estimates, spend data, or category screening. The key is to document the method honestly.
- Overclaiming renewable electricity. Keep evidence for contracts, certificates, and tariff claims, and be clear about the method used.
- Confusing consultant letters with assurance. A consultant letter can document support with calculations and methodology. Independent assurance is a separate engagement performed under assurance standards by an appropriate independent provider.
- Buying software before understanding the request. Software can help later, but it will not decide the boundary, interpret the customer wording, or write a credible response for you.
When to ask for help
It is reasonable to handle a simple data request internally if the boundary is clear, the data is easy to collect, and the customer is only asking for a basic response. It is worth getting help when the request is customer-specific, the deadline is tight, Scope 3 is involved, the customer asks for service-level emissions, or the wording mentions assurance, verification, consultant support, CDP, EcoVadis, or another formal platform.
Help is also useful when the company wants the first response to become a repeatable file. A good supplier response should make the next disclosure cycle easier, not just solve this month's deadline.
Need help turning this checklist into a customer-ready response?
Keslio helps suppliers interpret customer sustainability requests, collect the right data, calculate emissions, document assumptions, and prepare a response that can stand up to customer follow-up.
FAQs
Can we respond if our emissions data is incomplete?
Often, yes. The response should explain which data is complete, which data is estimated, which categories are excluded, and how the company plans to improve the data next time. Do not hide gaps. Document them clearly.
Is supplier GHG reporting the same as a full ESG report?
No. A supplier GHG request is usually narrower. It may only cover emissions data, a customer questionnaire, a service-level calculation, supporting documentation, or a specific platform response. A full ESG report is broader and usually not the first thing a supplier needs for a customer request.
Do we need carbon accounting software?
Not always. For a first or urgent customer response, a well-built workbook and a clear method may be enough. Software can be useful when reporting is recurring, data sources are complex, or multiple sites and business units need to report regularly.
What if the customer asks for service-level emissions?
Then the checklist needs an allocation method. You need to define which parts of your company footprint relate to the service, contract, product, or customer relationship, and document why the allocation method is reasonable.
What if the request asks for assurance or verification?
Pause and confirm the wording. Consultant support, a consultant letter, validation, verification, and independent assurance are not interchangeable. If independent assurance is required, that should be scoped separately with an appropriate assurance provider.
Related guides
- What to do when a customer asks for emissions data
- How to respond to a supplier sustainability questionnaire
- An introduction to Scope 1, Scope 2, and Scope 3 emissions
- A guide to the GHG Protocol
