Your Biggest Customer Just Asked for Your Emissions Data. Now What?

Scope 3 reporting is creating a trickle-down data demand across Australian supply chains. If your biggest customer just emailed asking for your carbon numbers, here's exactly what they need, why they're asking, and how to respond — even if you've never measured a single emission.

Carbonly.ai Team April 11, 2026 10 min read
Scope 3Supply ChainSmall BusinessASRSEmissions Data
Your Biggest Customer Just Asked for Your Emissions Data. Now What?

Last Tuesday, a 40-person electrical contractor in western Sydney forwarded us an email from their biggest client — a Tier 1 construction company. The subject line: "Supplier Sustainability Data Request — Action Required by 30 June."

The email contained a spreadsheet template asking for total Scope 1 and Scope 2 emissions in tonnes CO2-e, electricity consumption by state, fuel use by vehicle type, and a description of their measurement methodology. The contractor's operations manager had two questions. What does any of this mean? And if we ignore it, do we lose the contract?

The answer to the second question is: probably. Maybe not this year. But soon. And they're not the only small supplier in Australia getting these emails right now.

Why your customer suddenly cares about your emissions

This isn't a corporate sustainability team going rogue. It's regulatory gravity.

Under AASB S2 — the Australian Sustainability Reporting Standards — Group 1 entities started mandatory climate disclosures in January 2025. Group 2 kicks in from July 2026. Both groups get a one-year deferral on Scope 3, but that deferral has already expired for Group 1 reporters. They're disclosing their value chain emissions right now.

And here's the maths that matters for every small supplier: Scope 3 emissions are, on average, 26 times larger than a company's operational emissions, according to CDP's 2024 supply chain report. For a construction company or a retailer, purchased goods and services (Category 1) often make up 50% to 80% of their total Scope 3 footprint. Your customer can't report their emissions without reporting yours.

They have two choices. Estimate your emissions using spend-based industry averages — which makes their numbers look worse because averages assume everyone is average. Or get actual data from you — which is more accurate, looks better to auditors, and (this is the bit that should get your attention) gives them a reason to keep you on the approved supplier list.

Right now, only 15% of corporates have set Scope 3 supply chain targets, and just four in ten actively engage their suppliers on climate data. But that's changing fast. The companies reaching out to you are the early movers. The rest will follow once Group 2 reporting hits and they realise they can't file their AASB S2 disclosures without supplier data.

What they're actually asking for

The email your customer sent probably looks intimidating. But strip away the jargon, and the data request usually boils down to five things.

Your annual electricity consumption in kWh, broken down by state. This is your Scope 2. Pull it from your electricity bills. If you're in NSW, each kWh carries an emission factor of 0.64 kg CO2-e. Victoria is 0.78. South Australia is 0.22. These are the 2025 NGA Factors published by DCCEEW — the numbers the GHG Protocol and AASB S2 expect you to use for location-based reporting.

Your fuel consumption — diesel, petrol, LPG — in litres. This is your Scope 1. Fleet vehicles, generators, forklifts, anything with an engine you own or control. The NGA Factors workbook has emission factors for each fuel type. Diesel is roughly 2.68 kg CO2-e per litre (combustion only). Petrol is about 2.29.

Your natural gas consumption in GJ. Also Scope 1. If your business uses gas for heating, cooking, or industrial processes, your gas bill has the GJ figure. The emission factor is around 51.4 kg CO2-e per GJ for natural gas distributed in a pipeline.

Your total emissions in tonnes CO2-e. This is the sum. They want a single number for Scope 1, a single number for Scope 2, and ideally the emission factors and methodology you used. Don't overthink methodology — for most small businesses, this means "we used NGA Factors 2025 applied to activity data from utility bills and fuel records."

Whether you have a reduction target or plan. This one is optional for now. But it's increasingly appearing in tender evaluation criteria. South Australia's Department for Infrastructure and Transport already requires suppliers to disclose product-level carbon footprints and outline reduction actions. Queensland's new procurement policy from January 2026 puts even more weight on sustainability credentials.

That's it. No one is asking a 40-person electrician for a lifecycle assessment or a TCFD scenario analysis. They're asking: how much electricity and fuel did you use last year, and what does that convert to in CO2-e?

How to produce a basic emissions profile (even if you've never done this)

We're not going to pretend this is trivial. But it's not as hard as the sustainability consulting industry wants you to believe.

For a small business with one or two office locations and a vehicle fleet, you can produce a credible emissions profile in a day. Maybe two if your filing is messy. Here's the honest version of what that involves.

Gather 12 months of utility bills. Electricity, gas, water if requested. You need the consumption figures, not the dollar amounts. The kWh number on your electricity bill. The GJ number on your gas bill. If you can't find physical copies, most retailers (AGL, Origin, EnergyAustralia) have 12-month usage summaries in their online portals.

Gather 12 months of fuel records. If your fleet uses fuel cards, pull the annual statement. If not, your accounts payable probably has the invoices. You need total litres by fuel type. Don't stress about splitting it by vehicle — total litres is enough for a first pass.

Apply NGA Factors. Multiply each activity by its emission factor. The NGA Factors 2025 workbook is a free download from DCCEEW. Table 1 has electricity factors by state. Table 3 has stationary energy factors (gas). Table 4 has transport fuel factors. The workbook is an Excel file. You can do this calculation in a spreadsheet.

Sum it up. Add your Scope 1 (fuel + gas combustion) and Scope 2 (electricity) totals. Report in tonnes CO2-e.

For a worked example: a 30-person business in Melbourne consuming 120,000 kWh of electricity, 500 GJ of natural gas, and 40,000 litres of diesel across its fleet would report roughly 93.6 tonnes from electricity (120,000 x 0.78 / 1000), 25.7 tonnes from gas (500 x 51.4 / 1000), and 107.2 tonnes from diesel (40,000 x 2.68 / 1000). Total: about 226.5 tonnes CO2-e.

That's not a perfect number. We haven't accounted for refrigerant losses, waste, or business travel. But it covers 80-90% of a typical small business footprint, and it's backed by published government emission factors. That makes it credible. It's a starting point your customer can actually use instead of a spend-based estimate.

What "good enough" looks like — and what doesn't

Here's where we'll be direct, even if it's uncomfortable for us as a carbon accounting software company to say: for a small supplier responding to a first-time data request, a spreadsheet is probably fine.

Seriously. If you've got fewer than five sites and a dozen utility accounts, a well-structured spreadsheet with NGA Factors applied correctly is a legitimate response. Your customer's sustainability team will be relieved they got actual data instead of radio silence.

What's not good enough:

  • Guessing. "We think our emissions are about 200 tonnes" with no supporting data. Your customer needs to show their auditor where the number came from. "The supplier estimated" is not a methodology.
  • Using the wrong emission factors. We've seen suppliers grab a random number from Google and apply a US EPA factor to Australian electricity. NSW grid electricity at 0.64 kg CO2-e/kWh is very different from the US national average. Use NGA Factors. They're specifically designed for Australian reporting.
  • Dollar-based estimates when activity data exists. If your customer asked for kWh and you send them dollar spend, they'll convert it to emissions using a spend-based factor that makes your footprint look bigger than it actually is. Activity data (kWh, litres, GJ) always produces a more accurate — and usually lower — result.

We'll be honest about the limitation too. We're still figuring out the best way to help very small businesses (under 20 staff) respond to these requests efficiently without it costing them more than the data is worth. The tooling for this part of the market isn't great yet — not ours, not anyone's. Most carbon accounting software is built for the entity doing the reporting, not the entity being asked for data by someone else.

This is a competitive advantage if you move early

NettZero put it bluntly in a recent piece: "AASB S2 is not just a compliance standard for big business; it is a procurement standard for everyone else." That's exactly right.

Large companies are rewriting their tender documents. Sustainability criteria are showing up in RFPs that never had them. And the early data from CDP shows something telling — companies that engage their suppliers on emissions are almost seven times more likely to have a 1.5C-aligned transition plan. Those are the companies that are going to increasingly favour suppliers who can hand over data without a three-month back-and-forth.

Think about it from the procurement manager's perspective. They've got 200 suppliers. Forty of them respond with actual emissions data. The other 160 either don't respond or send something unusable. When contract renewal time comes and they need to cut their supplier list — who do you think survives?

This doesn't mean you need to become a sustainability company. It means you need a basic emissions profile, updated once a year, that you can share when asked. If you can produce that in a format your customer's system can ingest — even better.

At Carbonly, we're building features specifically for this use case: one-click emissions sharing that lets a small supplier produce a verified emissions profile and share it directly with a customer. We use AI to extract consumption data from your actual utility bills — the messy, inconsistent PDFs that no template-based system can read — and apply current NGA Factors automatically. But whether you use our platform, another tool, or a spreadsheet, the important thing is having a number you can defend.

What to do this week

Don't wait for the next data request to figure this out. Here's a realistic plan for a small business that's never tracked emissions.

Pull your last 12 months of electricity, gas, and fuel records into one folder. That's Monday's job. Download the NGA Factors 2025 workbook from DCCEEW. That's five minutes on Tuesday. By Wednesday, you can have a basic emissions number.

Then respond to your customer. Send the data, note the emission factors you used, and offer to update annually. That email alone puts you ahead of most of their supply chain.

Because here's what nobody says out loud: the bar is low right now. Most small suppliers aren't responding at all. Producing even a basic, defensible emissions figure makes you exceptional. That won't last — within two years, it'll be table stakes. But right now, it's a genuine differentiator.

And it might just be the thing that keeps your biggest contract.

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