Last updated: May 31, 2026. Someone on your team has received a customer email, portal notice, or sustainability questionnaire asking for emissions data. It may be one sentence long, or it may come with a long spreadsheet and a deadline. Either way, the first reaction is usually the same: what exactly are we supposed to send back?
The useful first move is not to calculate every possible emissions number. It is to slow the request down, understand what the customer is really asking for, and then collect the data that supports that specific response.
Short answer: if a customer asks for emissions data, start with the request itself. Check the deadline, reporting period, entities or sites covered, required scopes, response format, and evidence requirements. Then decide whether the customer needs a company footprint, service-level emissions, a supplier questionnaire response, CDP or EcoVadis support, a consultant letter, independent assurance, or supporting documentation. Only after that should you start collecting data.
Start with the request, not the spreadsheet
Most emissions requests are easy to misunderstand because they use familiar words in very specific ways. "Carbon data," "Scope 3," "supplier disclosure," "service emissions," "verification," and "consultant letter" can point to different kinds of work.
Before anyone starts building a workbook, save the original request. Keep the email, portal wording, attachments, screenshots, requested reporting year, deadline, customer contact, legal entity, site or service boundary, and required file format. If the request came through a portal, copy the exact wording before answers are entered or the screen changes.
This is not administrative housekeeping. It is how you avoid turning a narrow customer request into a broad ESG project. A full sustainability strategy may be useful later, but it rarely helps when the immediate problem is a customer deadline and a specific data request.
Work out what the customer is really asking for
Two requests can both ask for "emissions data" and still require very different responses. One customer may want your company's total Scope 1 and Scope 2 emissions. Another may want emissions allocated to the services you provide to them. Another may want a CDP response, EcoVadis evidence, methodology notes, reduction-plan information, a consultant letter, or independent assurance.
If you are new to the emissions language, Keslio's guides to Scope 1, Scope 2, and Scope 3 emissions and the GHG Protocol explain the accounting concepts in more detail. For this first response, the practical question is simpler: what answer would actually satisfy the customer's request?
This table is a useful way to triage the request before the calculation work begins.
| If the request says... | Likely response path | First practical step |
|---|---|---|
| "Company emissions," "corporate footprint," or "GHG inventory" | Company-level GHG calculation | Define the reporting boundary, reporting period, and Scope 1, Scope 2, and relevant Scope 3 data needs. |
| "Emissions for services provided to us" or "allocated emissions" | Service-level or contract-level allocation | Confirm the services, allocation basis, reference units, customer revenue or activity data, and what methodology notes are expected. |
| "CDP," "supply chain disclosure," or "customer requested CDP response" | CDP supplier disclosure support | Confirm the requested module, customer deadline, account access, and whether emissions, targets, governance, or supplier engagement sections are required. |
| "EcoVadis," "scorecard," or "evidence upload" | EcoVadis response and evidence preparation | Identify requested topics, supporting policies, evidence files, emissions information, and gaps that need an explanation. |
| "Consultant letter" | Consultant-letter support | Confirm what the letter must cover, what calculation work supports it, and whether the customer distinguishes it from independent assurance. |
| "Assurance," "verification," or "independent assurance" | Independent assurance route | Confirm whether an independent assurance provider is required and separate that work from calculation or advisory support. |
Collect the data in the right order
Once the response path is clear, data collection becomes much easier. You do not need to ask every department for every possible sustainability file. You need the information that supports the customer's requested answer.
For many supplier emissions requests, the first collection pass includes:
- The boundary: which legal entity, site, service, product, contract, or business unit is covered.
- The reporting period: calendar year, financial year, customer fiscal year, or a customer-specific period.
- Scope 1 data: fuel use, fleet fuel, refrigerants, generators, boilers, owned vehicles, or other direct emissions sources where relevant.
- Scope 2 data: electricity, purchased heating or cooling, utility bills, meter records, renewable electricity certificates, and supplier contracts.
- Relevant Scope 3 data: purchased goods and services, transport, waste, business travel, commuting, leased assets, or any categories the customer specifically mentions.
- Allocation data: revenue, headcount, floor area, hours, units, shipments, transaction volumes, or another driver if the customer asks for emissions tied to a service, product, site, or contract.
- Evidence: bills, invoices, reports, exports, assumptions, emission factors, and methodology notes that explain where the numbers came from.
The people involved will depend on your company. Finance may hold utility bills and spend data. Operations may hold fuel, fleet, logistics, and site information. HR may hold travel or commuting data. Account teams may understand the customer contract and the service boundary. A sustainability lead, if you have one, can coordinate the method and final response.
If your data is messy, say so clearly
Many companies receive customer emissions requests before they have a perfect GHG inventory. That does not always mean they cannot respond. First-year responses often use a mix of actual data, reasonable estimates, emission factors, assumptions, and data-quality notes.
The important thing is to be honest about the method. Which numbers are actual? Which are estimated? Which sites or activities are excluded? Which emission factors were used? What will improve in the next reporting cycle?
A response with clear limitations is usually stronger than a polished number with no evidence behind it. Do not invent data, hide known gaps, or remove uncertainty just to make the response look cleaner. If the request is material, high-risk, or tied to a contract obligation, get advice before submitting.
Know when the request is more specialized
Some customer requests go beyond a simple company footprint. The earlier you spot this, the easier it is to avoid rework.
Service-level emissions usually require a company or activity footprint plus an allocation method that connects emissions to the specific service provided to the customer. This is different from simply sending your company-wide emissions total.
Consultant letters and independent assurance are also different. A consultant letter may describe the consultant's support in preparing the calculation or methodology. Independent assurance is a separate service performed by an assurance provider under assurance standards. If the request uses assurance or verification language, confirm what the customer actually requires before assuming a consultant letter is enough.
CDP and EcoVadis requests often combine emissions data with governance, targets, policies, evidence files, and platform-specific questions. They are not just spreadsheet exercises. The response needs to match the platform and the customer's request.
If the request names a specific customer requirement, such as a Microsoft supplier GHG request, it may also have its own response path. Keslio's Microsoft supplier GHG reporting page explains that route separately.
Do you need software, or do you need help interpreting the request?
Carbon accounting software can be useful when you have many sites, large datasets, recurring annual reporting, integrations, dashboards, or a reporting workflow that will repeat every year.
But software is not always the first thing to solve. If the customer request is urgent, unfamiliar, customer-specific, or commercially sensitive, the first need is often interpretation: what does the customer want, what evidence will support it, and what can your team reasonably submit?
Once that is clear, software may still be useful. But buying a platform before understanding the request can slow the team down. The better question is: what is the smallest defensible response that answers the customer properly?
How Keslio can help
Keslio helps suppliers and service providers turn customer sustainability requests into clear, practical response projects. The work starts with the request wording, then moves into data collection, calculation, documentation, and customer-ready response support.
Support can include:
- Reviewing the customer request wording and deadline.
- Confirming the likely reporting scope and response path.
- Preparing a focused data request checklist for your internal team.
- Calculating Scope 1, Scope 2, and relevant Scope 3 emissions.
- Supporting service-level or customer-specific allocation where required.
- Preparing methodology notes, assumptions, and evidence packs.
- Supporting CDP, EcoVadis, or supplier portal responses where in scope.
- Preparing consultant-letter support where appropriate.
- Helping with one round of customer clarification.
- Preparing annual refreshes so the next request is easier.
What this service is not
This service is designed for supplier-request interpretation, GHG calculation support, documentation, and customer-ready response preparation. It is not a substitute for every specialist service that may be needed.
Keslio does not provide, through this service:
- Independent assurance unless separately arranged with an appropriate assurance provider.
- Legal advice.
- Customer endorsement, customer approval, or platform approval.
- Guaranteed acceptance by a customer, CDP, EcoVadis, Microsoft, or any other organization.
- A broad ESG strategy unless separately scoped.
FAQ
Can we respond if we do not have complete emissions data?
Often, yes. The response may need estimates, assumptions, data-quality notes, and a clear explanation of limitations. The key is to avoid unsupported numbers and document how each figure was calculated.
Do we need Scope 3 emissions?
It depends on the request. Some customers ask only for Scope 1 and Scope 2. Others ask for relevant Scope 3 categories, service-level emissions, or value-chain information because they are calculating their own Scope 3 footprint. Check the exact wording before collecting every category.
What should we collect first?
Start with the request itself, then collect the reporting period, organizational boundary, site list, utility bills, fuel records, travel data, spend or purchasing data, logistics data, and any customer-specific allocation drivers. The exact list should be narrowed after the request is interpreted.
What if the customer asks for service-level emissions?
Service-level emissions usually require a company or activity footprint plus an allocation method that connects emissions to the service provided to that customer. You will need to confirm the service boundary, allocation driver, reporting period, and methodology expectations.
What if the customer asks for assurance or verification?
Independent assurance is separate from consultant calculation support. If the request uses assurance or verification language, confirm whether an independent assurance provider is required before assuming a consultant letter is enough.
Do we need carbon accounting software?
Not always. Software can help with repeatable reporting and larger datasets. For a first customer request, urgent deadline, or unusual customer-specific requirement, interpreting the request and preparing a defensible response may matter more than selecting a platform.
Can Keslio review the request before quoting?
Yes. Keslio can review the request wording first, identify the likely response path, and then quote a focused support project based on the work actually required.
