Is Scope 3 Reporting Mandatory? What the GHG Protocol Says

The short answer is that it depends entirely on which rulebook binds you — and the two most common answers you will hear are both right, for different readers. Under the GHG Protocol Corporate Standard itself, Scope 3 reporting is optional. Under the European Sustainability Reporting Standards and under IFRS S2, it is a required disclosure. Finance teams get caught out because the frameworks that reference the GHG Protocol impose more than the GHG Protocol does.

What the GHG Protocol Corporate Standard actually requires

The Corporate Standard is unambiguous in its own words. Chapter 4 states:

Companies shall separately account for and report on scopes 1 and 2 at a minimum.

And on the next breath, in the same chapter:

Scope 3 is an optional reporting category that allows for the treatment of all other indirect emissions.

Chapter 6, under the heading for identifying Scope 3 emissions, describes the exercise as an optional step. So a company reporting against the Corporate Standard alone, with no other obligation in play, meets the standard by reporting Scopes 1 and 2 and nothing more.

That is the whole of the Protocol’s own position. It is worth stating plainly because a great deal of published commentary asserts the opposite, and because the separate Corporate Value Chain (Scope 3) Accounting and Reporting Standard, released in 2011, is frequently misread as making Scope 3 compulsory. It does not. It governs how to account for Scope 3 if a company chooses to, or is required to by something else.

Where Scope 3 does become mandatory

ESRS E1 under the CSRD

ESRS E1 paragraph 44 requires the undertaking to disclose, in metric tonnes of CO2 equivalent, its gross Scope 1 emissions, its gross Scope 2 emissions, its gross Scope 3 emissions, and its total GHG emissions. Scope 3 is not an optional limb of that list; it sits alongside the other two.

The application requirements then send the preparer back to the Protocol. AR 39 opens by telling the undertaking that, when preparing the information required by paragraph 44, it shall:

consider the principles, requirements and guidance provided by the GHG Protocol Corporate Standard (version 2004).

AR 39 also sets the gas coverage: CO2, CH4, N2O, HFCs, PFCs, SF6 and NF3, with additional greenhouse gases considered where significant.

Granularity comes from paragraph 51, which requires disclosure for each significant Scope 3 category — that is, each category that is a priority for the undertaking — with the application requirements directing a screen across all fifteen categories to establish which those are. So the obligation is not merely a single aggregate Scope 3 number; it is a screened, category-level disclosure.

IFRS S2

IFRS S2 takes a different route to a similar place. Paragraph 29(a)(i) requires the entity to disclose its absolute gross greenhouse gas emissions generated during the reporting period, expressed in metric tonnes of CO2 equivalent. Paragraph 29(a)(ii) then requires the entity to measure those emissions in accordance with the Greenhouse Gas Protocol: A Corporate Accounting and Reporting Standard (2004), unless a jurisdictional authority or an exchange on which the entity is listed requires a different measurement method.

So under IFRS S2 the Protocol is not merely something to consider — it is the prescribed measurement methodology, with a jurisdictional carve-out.

This changed in December 2025. The ISSB issued Amendments to Greenhouse Gas Emissions Disclosures, effective for annual reporting periods beginning on or after 1 January 2027, with earlier application permitted. The amendments allow entities to limit Scope 3 Category 15 to financed emissions and exclude derivatives; extend the jurisdictional relief from the GHG Protocol measurement method so that it can apply to part of an entity rather than only the whole; introduce a parallel relief for using global warming potential values other than those in the latest IPCC assessment; and replace the mandatory six-digit GICS classification for financed emissions by industry with a choose-and-justify approach.

The fifteen Scope 3 categories

Where Scope 3 is required, the structure comes from the Scope 3 Standard. Eight upstream categories: purchased goods and services; capital goods; fuel- and energy-related activities not included in Scope 1 or Scope 2; upstream transportation and distribution; waste generated in operations; business travel; employee commuting; and upstream leased assets. Seven downstream: downstream transportation and distribution; processing of sold products; use of sold products; end-of-life treatment of sold products; downstream leased assets; franchises; and investments.

A sixteenth category, for other value chain activities, is under consideration in the current revision of the Scope 3 Standard. It is draft material, not standard text.

Scope 2 has a conditional requirement too

A parallel point that catches people out: the Scope 2 Guidance of January 2015 requires dual reporting, but conditionally. Where a company has operations in markets that provide product- or supplier-specific contractual data, it must report Scope 2 two ways — once on the location-based method and once on the market-based method — and label each result. Where a company has operations only in markets without such data, a single location-based result is reported. The guidance adds that not having contractual data for every site does not of itself cause noncompliance.

So neither “Scope 2 always needs two numbers” nor “Scope 2 needs one number” is right on its own.

What this means in practice

The practical test is not “does the GHG Protocol require Scope 3?” but “what am I reporting under?” An in-scope CSRD undertaking has a Scope 3 disclosure obligation with category-level granularity. An entity applying IFRS S2 has a Scope 3 disclosure obligation and a prescribed measurement methodology. A company voluntarily reporting against the Corporate Standard has neither, and is fully compliant reporting Scopes 1 and 2 only.

For finance teams the consequence is that the data architecture question — supplier spend data, logistics data, product use assumptions — is driven by the disclosure framework, not by the Protocol. And because the Protocol is itself mid-revision, and mid-revision, with a consolidated draft standard estimated for Q2 2027 and publication for Q4 2028, the methodology layer is not static either.

A note on sources

The GHG Protocol quotations above are from the Corporate Standard’s own text. The ESRS quotations are taken from EFRAG’s Knowledge Hub rendering of the delegated act rather than from the Official Journal text of Commission Delegated Regulation (EU) 2023/2772; EFRAG drafted the standards, so this is not third-party commentary, but it is not the Official Journal either. The pages used are a post-Omnibus amended version, and ESRS E1 is itself subject to a live amendment process, so the paragraph references should be checked against the version that applies to your reporting period.

Frequently asked questions

Is Scope 3 mandatory under the GHG Protocol? No. The Corporate Standard requires Scopes 1 and 2 at a minimum and describes Scope 3 as an optional reporting category.

Is Scope 3 mandatory under the CSRD? Yes. ESRS E1 paragraph 44 lists gross Scope 3 emissions as a required disclosure, with category-level disclosure for significant categories under paragraph 51.

Does IFRS S2 require Scope 3? Yes, and it also prescribes the GHG Protocol Corporate Standard as the measurement method, subject to a jurisdictional carve-out that the December 2025 amendments widened.

Do I have to report all fifteen categories? Under ESRS E1 the requirement is to screen all fifteen and disclose the significant ones, not to report every category in full.

Build your sustainability reporting expertise with Learnsignal

Scope boundary decisions, the required-versus-optional distinction and the interaction between the Protocol and the disclosure frameworks are exactly the areas where reporting goes wrong. Our CPD courses on sustainability and climate reporting work through them with the standards open. You may also find our guides to carbon accounting and Scope 3 emissions, IFRS S1 and S2 and CSRD compliance useful. The primary texts are published by the GHG Protocol.