If your procurement team has filled in a Carbon Reduction Plan questionnaire, or your ESG (environmental, social and governance) team has been asked by a customer for supply-chain emissions data, you already know most businesses struggle to produce real numbers for this paperwork.
Digital activity- your website, your cloud services, your email and ad platforms – produces emissions. Most of it sits in your Scope 3 (emissions from your supply chain rather than your own operations), the hardest category to measure and the one procurement panels and ESG teams are now starting to ask about. This guide to carbon reporting sets out, plainly, what the current rules actually require, who they reach, and how to build a digital carbon report that holds up when someone checks it.
What is digital carbon reporting?
Digital carbon reporting is the practice of measuring, recording and disclosing the greenhouse gas emissions produced by your digital activity: the energy used to load your website, run your cloud infrastructure, send your email and serve your online advertising, along with the data centres and networks behind them.
Done properly, it is repeatable rather than a one-off estimate. It gives you a baseline, a method you can defend under questioning, and a way to show progress over time. For a business answering to a procurement panel or an ESG team, that is the difference between a claim and evidence.
What UK carbon reporting rules actually require
Three separate mechanisms get blurred together in most commentary on this topic. They reach different companies, in different ways, and conflating them is where most carbon reporting advice goes wrong.
PPN 006: a government contract threshold, not a blanket rule
If you are bidding for a UK central-government contract, the relevant instrument is Procurement Policy Note 006 (PPN 006).
This guidance, published by the Cabinet Office, applies to in-scope central government contracts in excess of £5 million, including VAT, per annum.
Bidding suppliers must provide a Carbon Reduction Plan when responding to an in-scope procurement, confirming commitment to achieving Net Zero by 2050, detailing current emissions, and setting out the environmental management measures in place.
This is a condition of participation on a specific contract size, not a general legal duty on every UK business. If you are not bidding for a central-government contract above that threshold, PPN 006 itself does not reach you directly. If you are, it is one of the few places in UK carbon reporting where the requirement, and the threshold that triggers it, is named precisely and checkable at source.
SECR: large companies’ own Scope 1 and 2 obligation
The Streamlined Energy and Carbon Reporting (SECR) regime is set out in The Companies (Directors’ Report) and Limited Liability Partnerships (Energy and Carbon Report) Regulations 2018 (SI 2018/1155).
SECR applies to UK quoted companies, and to “large” unquoted companies or LLPs that meet at least two of: turnover above £36 million, balance sheet total above £18 million, or 250 or more employees.
SECR requires Scope 1 (combustion of fuel or gas) and Scope 2 (purchased electricity) reporting; it does not mandate Scope 3 reporting.
Two things matter for a supplier reading this guide. First, that threshold sits well above typical SME size, so most smaller suppliers are outside SECR as a direct obligor. Second, the pressure you may feel from a larger customer to supply your own emissions data is not SECR’s legal text reaching into your business. It is that customer choosing, often informally, to ask its suppliers for data to build a fuller picture voluntarily.
The EU sustainability directive: indirect pressure, and narrower than it was
The European Commission’s corporate sustainability reporting page sets out the starting point: EU rules require large companies and listed companies to publish regular reports on the social and environmental risks they face, and on how their activities impact people and the environment. Those rules sit in the Corporate Sustainability Reporting Directive (CSRD). A large customer with that obligation may ask you for figures to help complete its own report.
That scope has since been cut back. The Commission’s Omnibus simplification package of 26 February 2025 proposed to apply the CSRD only to the largest companies, those with more than 1,000 employees, and to ensure that reporting requirements on large companies do not burden smaller companies in their value chains. The European Parliament and the Council reached political agreement on the simplification omnibus on 9 December 2025. The amending law is Directive (EU) 2026/470, so check its final thresholds against the legal text rather than the proposal before you rely on them.
An ordinary UK SME supplier is not the company this directive is aimed at. If it reaches you at all, it is because one of your customers is obligated and is asking you for data, not because it names you.
Why Scope 3 is where most of this sits
Across all three mechanisms, the hard part is the same: most digital emissions are Scope 3, meaning they sit in your supply chain rather than on your own meter. Your hosting provider, your CDN and your SaaS tools all contribute.
The GHG Protocol describes its Corporate Value Chain (Scope 3) Standard, released in 2011, as the only internationally accepted method for companies to account for value chain emissions. Users of the standard can account for emissions from 15 categories of Scope 3 activities, both upstream and downstream of their operations.
It is worth being precise about what this standard is: a voluntary accounting method that a reporting company chooses to use, not a body that requests data from anyone itself. A customer that asks you for Scope 3 figures is acting on its own reporting duty, structured around this standard’s categories, not on a request from the standard itself.
For the detail on where digital Scope 3 boundaries sit and what a website audit can honestly measure, see our guide to Scope 3 emissions in digital services.
Producing a digital carbon report that holds up
You do not need a sustainability department to do this well. These steps produce a report a procurement panel or an ESG team can check.
1. Map your digital footprint
List everything that runs online: your website, hosting, cloud storage, email platform, advertising accounts and any apps or tools your team uses daily. You cannot measure what you have not mapped, and this inventory is the backbone of everything that follows.
2. Measure your website’s emissions
Your website is usually the most visible and most fixable part of the picture. Measure its page weight and the carbon produced per visit, then multiply by your monthly traffic. A professional website sustainability audit does this accurately and flags the heaviest pages, where the quickest reductions live. For the fuller picture of what a website carbon footprint assessment covers, see our dedicated guide.
3. Choose a recognised framework
Pick an established methodology rather than inventing your own. The GHG Protocol is the global standard for Scope 3 accounting broadly, and the Sustainable Web Design model (SWDM), currently on Version 4, is widely used for estimating website emissions specifically. Using a recognised framework means your numbers can be compared and checked by whoever is reading your report.
4. Turn the data into a report your audience can check
A procurement panel or an ESG team needs plain language, not a spreadsheet of unexplained figures: total carbon per year, the trend against your baseline, and the method you used, named. State clearly whether a figure is modelled or measured, since the two answer different questions. Modelled carbon, from tools built on frameworks such as SWDM, is a sound benchmark. A tender response or an ESG report more often expects figures built from your own measured page weight and real traffic.
5. Set a reduction target, tied to specific actions
A report without a target is just a number. Commit to a measurable reduction over a defined period, then tie it to specific actions: lighter pages, more efficient hosting, fewer third-party scripts.
6. Report on a regular cadence
Digital carbon reporting only builds trust when it is consistent. Repeat the measurement quarterly or annually so you can show progress against a baseline rather than a single snapshot, and catch the slow creep of page bloat before it erodes earlier gains.
Carbon Delta: the before-and-after figure procurement and ESG teams actually want
What a tender panel or an ESG team usually wants is not a single carbon figure but a measured change: the difference between the site you had and the one you have now. A website sustainability audit produces exactly this, called a Carbon Delta: before-and-after data on page weight and carbon per page view, exportable directly into an ESG digital reporting framework or a formal tender response.
That is the difference between stating “we are reducing our emissions” and showing the measured amount by which you have. Our websites emit up to 83% less CO₂ than Website Carbon’s published global average of about 0.36g per page view, performing at 0.06g to 0.20g per page view. A Carbon Delta gives you the same kind of evidenced figure for your own site, rather than borrowing ours.
Common digital carbon reporting mistakes to avoid
Three errors trip up most first attempts. The first is measuring once and never again, which leaves you with a stale figure that proves nothing to a panel checking for a trend. The second is ignoring Scope 3, which leaves out the largest share of most organisations’ digital emissions. The third is overclaiming, where a modest reduction gets dressed up as carbon neutrality or an unqualified net zero claim the evidence does not support. For a procurement panel or an ESG team doing due diligence, honest, modest, repeatable numbers consistently beat an impressive claim they cannot verify.
If you would rather have the measurement handled for you, a structured audit removes the guesswork and gives you a Carbon Delta you can hand straight to a tender panel, a client or a board. For the wider context behind why this matters to a growing business, see our guide to digital sustainability for UK businesses. You can talk to Agnikii Digital about a digital carbon report built around your business.