Scope 3 reporting: which rule actually applies to you

Where Scope 1 and Scope 2 stop

“Scope 3” is an accounting boundary from a voluntary standard, while your reporting duty comes from UK law and FCA rules that each draw their own line across it.

That mismatch is why the honest answer to “do I have to report Scope 3?” is four different answers depending on what kind of organisation you are.

And most Scope 3 mistakes are boundary mistakes made two steps earlier, in Scope 1 and Scope 2.

The test the GHG Protocol applies is ownership or control of the emitting source, and it is applied to the source, not to the activity [3].

The test is the source, not the activity

A car your company owns and fuels burns Scope 1 fuel.

The same journey in an employee’s own car is Scope 3, because you do not own or control the vehicle — even where you paid for every litre.

A leased vehicle you operate falls in Scope 1 or 2; one you do not operate falls in Scope 3 category 8, upstream leased assets [3].

Your electricity has a Scope 3 tail

Electricity you buy is Scope 2, but the transmission and distribution losses on the way to you, and the extraction and refining of the fuel that generated it, are Scope 3 category 3 [3].

That last one catches people out constantly: your electricity has a Scope 3 tail, and it is usually the easiest material category to calculate because the factors are published.

If you are still settling the first two boundaries, start with Scope 1, 2 and 3 emissions explained, then come back — a Scope 3 inventory built on an unsettled Scope 1 boundary double-counts or drops whole categories.

The fifteen categories

The GHG Protocol Corporate Value Chain (Scope 3) Standard defines exactly fifteen categories — eight upstream, seven downstream — and they are mutually exclusive by design so that nothing inside one company’s inventory is counted twice [3].

UK SRS S2 adopts that taxonomy rather than inventing its own [2].

Not every category will be material to you, and the Standard does not ask you to report all fifteen — it asks you to assess all fifteen and disclose the material ones, with your reasons for the rest.

Select a category below for its boundary and where its data usually comes from.

Two categories dominate most non-financial inventories: category 1 (purchased goods and services) and category 11 (use of sold products).

For banks, insurers and asset managers, category 15 (investments) is usually larger than everything else combined — see financed emissions.

For the concept of Scope 3 itself, with worked examples by category, see the Scope 3 emissions guide; for the standard that defines them, see the GHG Protocol.

Which Scope 3 rule applies to you

Four questions, and the answer is one of four genuinely different duties — not four shades of the same one.

This computes from what you tell it; nothing is sent anywhere.

The four duties, written out

Everything the component above can tell you is also here, in plain text, because a fact that only exists inside a script is a fact nobody can quote.

A secondary listing under UKLR 14 or 15 sits outside the full obligation: the FCA proposes a statement naming the sustainability requirements that apply in your home jurisdiction instead [5].

If you are unsure whether UK SRS reaches you at all, the scope question is answered properly on UK SRS thresholds.

The Scope 3 that SECR already makes mandatory

Almost every UK guide says some version of “Scope 3 is not required under SECR”. For large unquoted companies and LLPs that is wrong, and the government guidance says so in the word “mandatory”.

The Environmental Reporting Guidelines set out what each scope requires, regime by regime [6].

Its Scope 3 row reads, verbatim:

“Mandatory for large unquoted companies and LLPs to disclose energy use and related emissions from business travel in rental cars or employee-owned vehicles where they are responsible for purchasing the fuel. Other Scope 3 emissions voluntary, but strongly encouraged where this is a material source of emissions.”

Environmental Reporting Guidelines, March 2019, scope table [6]

The same document’s inclusion list repeats it: “Fuel used in personal/hire cars on business use (including fuel for which the organisation reimburses its employees following claims for business mileage)” [6].

This is commonly called the grey fleet — vehicles your people drive on your business that your company does not own.

What the regulation actually says

The statutory hook is narrower than most summaries suggest.

Schedule 7 Part 7A paragraph 20D(1)(b) of the 2008 Regulations, as inserted by SI 2018/1155, requires emissions “resulting from activities for which the company is responsible involving … the consumption of fuel for the purposes of transport” [7].

The test is responsibility for buying the fuel, not ownership of the vehicle — which is exactly why the grey fleet is caught.

And the Protocol calls it Scope 3 too

And it is unambiguously Scope 3 in the Protocol’s own words: category 6 (business travel) covers “automobile travel (e.g., business travel in rental cars or employee-owned vehicles other than employee commuting to and from work)” [3] — the identical phrase the Guidelines use.

So the correct sentence is: Scope 3 is largely voluntary under SECR, except for the grey-fleet slice of category 6, which is mandatory for large unquoted companies and LLPs.

The full SECR picture, including thresholds and the intensity ratio, is on the SECR reporting guide.

UK SRS S2, Appendix C, paragraph C4

The Scope 3 transition relief is in UK SRS S2, and it is worth reading rather than paraphrasing — because what it does not say matters more than what it does.

It is in S2, and it is often cited to S1

It is frequently miscited as “UK SRS S1 Appendix C4”.

That paragraph does not exist: UK SRS S1’s Appendix C is Sources of guidance and runs C1 to C3 only, and S1’s transition provisions are in Appendix E [1].

The Scope 3 relief reads, in full:

“C4 An entity that applies this Standard is not required to disclose its Scope 3 greenhouse gas emissions (see paragraph 29(a)) which includes, if the entity participates in asset management, commercial banking or insurance activities, the additional information about its financed emissions (see paragraph 29(a)(vi)(2) and paragraphs B58–B63A).”

UK SRS S2, Appendix C, DBT, 25 February 2026 [2]

What C4 does not say

There is no time limit in it.

That omission is deliberate, and you can see it by reading the paragraphs on either side.

C1 grants relief from comparatives “in the first annual reporting period” [2].

C3 permits a non-GHG-Protocol measurement method “in the first annual reporting period in which an entity applies this Standard” [2].

C4 uses no such phrase.

Instead, C6 makes the availability of C3 and C4 “subject to any rules, requirements, regulations or legislation … determined by the Financial Conduct Authority” [2].

So the standard grants an open-ended relief and hands the FCA the job of closing it — which is what CP26/5 proposes to do.

C5: you never have to rebuild the year you skipped

C5 adds a quieter benefit: an entity using C3 or C4 “is permitted to continue to use those reliefs for the purposes of presenting information as comparative information in subsequent reporting periods” [2].

You do not have to retrospectively build the year you were excused from.

The rest of the standard the relief sits inside — the four pillars, scenario analysis and the other metrics and targets — is covered on UK SRS S2.

Every date that matters

Two of these dates are law, one is a publication, and the rest are proposals in a consultation that has closed but not yet concluded.

Treating the last group as settled is the most common error in UK Scope 3 planning right now.

The full cross-regime picture is on the UK SRS timeline.

What an “explain” has to actually say

Comply-or-explain is not a softer mandate that hardens later. Under the FCA’s proposal it is the permanent end state for listed-company Scope 3.

CP26/5 is explicit: “Even once the transition reliefs end, listed companies in these categories would report against UK SRS S2 Scope 3 provisions on a ‘comply or explain’ basis” [5].

That is a materially different planning assumption from “mandatory in 2028”, and it is the opposite of what most summaries say.

But the explain is not a free pass, because its contents are prescribed.

Where a company chooses to explain, the FCA proposes to require it to [5]:

Why the paragraph list is the hard part

Paragraph-level identification is the demanding part.

“We do not currently report Scope 3” does not satisfy it; naming the S2 paragraphs you are not meeting, and a dated plan to meet them, does.

Using the relief keeps your compliance statement. Explaining might not.

This is the sharpest practical distinction on the page, and it comes from two documents that have to be read together.

Paragraph 73A: the relief is free, the climate-only provision is not

UK SRS S1 paragraph 73A deals with what the reliefs cost you.

An entity using S1’s climate-only provision (E3) “is not permitted to assert compliance with UK SRS S1” [1].

But an entity using one or more of the three provisions — S1 E3, S2 C3, S2 C4 — “is not prevented from asserting compliance with UK SRS S2, but it shall disclose its use of those provisions alongside its statement of compliance” [1].

So taking the Scope 3 relief does not cost you your UK SRS S2 compliance statement.

You disclose that you took it, and you remain compliant.

Explaining is not the same as being excused

Choosing to explain after the relief expires is a different matter.

CP26/5 warns: “by opting to ‘explain’ rather than to ‘comply’ in relation to Scope 3 emissions, an issuer may not be able to state compliance with the UK SRS” [5].

The practical consequence is a cliff edge in 2028 that has nothing to do with penalties: a company that drifts from “relief” to “explain” without building capability may quietly lose the ability to claim compliance in its annual report.

Deciding what is material — and disclosing how you decided

UK SRS S2 sets no numeric threshold, which is a design choice rather than an oversight [2].

The Standard requires you to assess all fifteen categories and disclose the material ones, together with the process by which you decided [2].

Screen everything cheaply before measuring anything expensively

The GHG Protocol recommends a screening assessment first — rough spend-based or industry-average estimates across all fifteen — before spending anything on primary data [3].

The Standard’s own criteria for prioritising are size, influence, risk, stakeholder expectation, outsourcing and sector guidance [3].

A category can be excluded where it is small, offers little reduction opportunity and is not relevant to your business model — provided the exclusion is disclosed and justified [3].

The 1% rule of thumb is not in any standard

The 1% convention some consultancies quote appears in no standard: it is a rule of thumb, and presenting it as a regulatory threshold is a mistake an assurance provider will find.

Where double materiality applies to you instead, that is a different assessment entirely — see double materiality assessment.

Why Scope 3 is hard — the UK’s own evidence

The UK government asked, and 184 organisations answered.

DESNZ ran a Call for Evidence on Scope 3 in the UK reporting landscape from 19 October to 14 December 2023, and published its analysis in May 2024 [10][11].

It is the best UK-specific dataset on this subject and it is almost never cited.

Six named data problems

So the principle is not seriously contested — the practice is.

Complex data requirements were raised by 65 respondents, the single most frequent theme, resolving into six named problems [11]:

On cost, respondents named internal staff time (39 responses), external audit and verification (31) and data collection and IT (18) [11].

On benefit: transparency and reputation (33), identifying emission hotspots for targeted reduction (29), and benchmarking against peers (10) [11].

The five tiers of data, and the obligation to climb them

The GHG Protocol sets a preference order for data, and UK SRS S2 turns your position in it into a disclosure [2][3].

The obligation is not only to report the mix but to publish a plan to improve it, with timelines [2].

That converts supplier engagement from an initiative into a disclosed commitment you will be measured against next year.

The practical move is not to lift everything by one tier — it is to lift the two or three largest categories to tier 1 and leave the rest honestly labelled.

Category 15 and financed emissions

For asset managers, commercial banks and insurers, category 15 is not one of fifteen categories — it is the inventory.

UK SRS S2 paragraphs B58 to B63A set additional requirements for financed emissions, and Appendix C4 explicitly extends the Scope 3 relief to cover them [2].

That second point is easy to miss and financially significant: a bank taking the C4 relief is excused its financed emissions in the same breath as the rest of its Scope 3.

PCAF is the method, and it scores its own data

The measurement standard is PCAF’s Global GHG Accounting and Reporting Standard, whose third edition was published in December 2025 [8].

The attribution method allocates a counterparty’s emissions to you in proportion to your financial exposure — outstanding amount over the counterparty’s total enterprise value or property value, applied to their emissions [8].

PCAF also requires a data quality score from 1 to 5 for each asset class, so the weakness of the underlying data is disclosed rather than buried [8].

Why your lender wants your SECR number

There is a feedback loop worth naming: a bank’s PCAF score improves when its borrowers report their own emissions, which is why lenders increasingly ask for SECR or UK SRS S2 data in covenants.

Deeper treatment of the asset classes and attribution factors is on uksrs.finance.

Getting data out of suppliers

Category 1 is the largest category for most non-financial organisations and the one you control least.

The sequence that works is the one the GHG Protocol recommends: screen first, then spend money only where the screening says it matters [3][4].

Expect refusals, and plan for them: the DESNZ evidence names confidentiality as a distinct barrier from capability [11].

A supplier that will not send a number will often confirm a method, and a confirmed method beats an unexplained estimate at assurance.

Freight, travel and the categories that move

Four of the fifteen categories are about moving things, and they are the ones most often misallocated.

Category 4 is upstream transportation and distribution — goods coming to you, and third-party logistics you pay for [3].

Category 9 is downstream transportation and distribution — distribution of what you sell, where you are not paying for the freight [3].

Travel versus commuting

Category 6 is business travel, and category 7 is employee commuting; the dividing line is the journey’s purpose, not its mode [3].

Sea freight, and why it is not in your SECR figure

Sea freight is a common case because it is high-volume, low-intensity and usually subcontracted, which puts it in category 4 or 9 rather than in your SECR transport figure [6].

The Environmental Reporting Guidelines are explicit that subcontracted goods transport is outside the mandatory SECR energy figure and may be reported separately as Scope 3 [6].

So a logistics-heavy business can have a very large Scope 3 and a small mandatory SECR number, which is not an inconsistency — it is the two boundaries doing different jobs.

Factors, tools and data providers

Two things determine whether a Scope 3 number survives scrutiny: the factor you used, and whether you can still say which version it was a year later.

For UK activity data, the DESNZ conversion factors are the default tier-3 source and are republished annually [11].

What UK reporters actually use

Respondents to the DESNZ Call for Evidence named the factors, GHG Protocol guidance, Environmental Product Declarations, RICS whole-life carbon assessments, ecoinvent, employee travel surveys, and environmentally extended input-output models as their working sources [11].

That list is a reasonable procurement checklist: a tool that cannot ingest at least the factors, EPDs and an EEIO model will not cover a full inventory.

Version the factor, not just the number

Version the factor, not just the number.

An assurance provider will ask which year’s factor produced a given tonne, and a spreadsheet that overwrote last year’s cannot answer.

Platform selection, including what to ask vendors about audit trails, is covered on carbon reporting software.

Public sector Scope 3

UK public bodies sit under a different instrument, and reading SECR guidance at them produces the wrong answer.

Which instrument applies

Central government departments and their arm’s-length bodies report under HM Treasury’s Sustainability Reporting Guidance, which sets its own boundary and its own required disclosures [13].

That guidance directs bodies in SECR scope to align with the Environmental Reporting Guidelines for the SECR elements, so the two interlock rather than replace each other [6][13].

Procurement is the public-sector lever

The practical difference is procurement: a public body’s largest Scope 3 category is almost always category 1, and it has contractual leverage over suppliers that a private company does not.

This page treats the public sector as a boundary case rather than its subject; the obligations above are written for companies and LLPs.

Assurance readiness

No UK rule currently compels assurance over Scope 3 — but the FCA proposes to compel you to say whether you obtained it [5].

Where a company states it has assurance, the proposal requires it to name the assurer, the standard applied and the level obtained [5].

The benchmark standard is ISSA (UK) 5000, the FRC’s sustainability assurance standard, effective for engagements covering periods beginning on or after 15 December 2026 [9].

It is profession-agnostic: assurance practitioners need not be statutory auditors [9].

What an assurance provider actually asks for

The gap between a self-reported Scope 3 figure and an assurable one is almost always documentation rather than arithmetic.

Limited versus reasonable assurance

Limited assurance concludes that nothing came to the practitioner’s attention suggesting material misstatement; reasonable assurance is a positive opinion and a great deal more work [9].

Most first-year Scope 3 engagements are limited, and are still enough to expose a missing calculation trail.

Wider assurance context is on sustainability assurance.

Finding a verification body

There is no statutory register of Scope 3 verifiers, which is the honest answer to a question people ask expecting a list.

The FRC operates an interim register of sustainability assurance practitioners as the market develops [9].

How to filter the market

Beyond that, the practical filters are: does the practitioner work to ISSA (UK) 5000, have they assured value-chain data rather than only Scope 1 and 2, and will they do a dry run before the first reporting period.

A dry-run engagement in a year when nothing is mandatory is the cheapest way to find out that your calculation trail is a spreadsheet nobody can reconstruct.

Ask for the finding letter, not just the opinion — the findings are where next year’s work is written down.

Base years, acquisitions and restatement

A Scope 3 target is meaningless without a base year, and a base year is fragile the moment the company changes shape.

UK SRS S2 paragraph B34, incorporating S1’s paragraph B11, requires recalculation of base year emissions on a significant event or significant change in circumstance [2].

What a transaction does to the boundary

Acquisitions expand the organisational boundary and disposals contract it, and the GHG Protocol requires the same boundary across all categories [3].

Set the recalculation policy before the first transaction rather than after, because writing the threshold once the answer is known is the thing an assurance provider is trained to look for.

Where the change is material, restate and disclose the restatement rather than quietly rebasing [2].

All of that reduces to one question you can answer today.