GHG Protocol and ISO’s Consolidated Corporate Standard: What Companies Should Do Before 2028

The announcement is more than a standards rebrand

 

On 29 July 2026, the Greenhouse Gas Protocol confirmed what had been signalled for ten months: it and the International Organization for Standardization will stop maintaining two separate corporate carbon accounting standards and publish one.

The distinction between this and the September 2025 partnership announcement matters more than it first appears. The 9 September 2025 agreement was an intention. It named ISO’s 1406X family and the GHG Protocol’s corporate standards and said the two organisations would harmonise them. It set no scope and no dates. The July 2026 update names the exact documents being folded together, describes the shape of the result, and attaches a schedule: one integrated public consultation in Q2 2027, publication in Q4 2028.

It also carries a cost that has gone largely unremarked. A public consultation draft of the GHG Protocol’s revised Corporate Standard was originally due in the second quarter of 2026. It has been shelved in favour of the unified draft a year later. Companies that have been waiting since 2022 for a revised Corporate Standard will now wait until at least 2029 to report under one.

Two organisations are not merging. ISO is a membership body of 177 national standards organisations; the GHG Protocol is a WRI–WBCSD initiative that appointed its first chief executive, Tim Mohin, only in April this year. Each ratifies separately, and the development plan sets out how. Once the Independent Standards Board approves a draft, it goes concurrently to the GHG Protocol Steering Committee for ratification and to ISO/TC 207/SC 7 for approval, which requires a two-thirds majority of permanent members with no more than a quarter of votes cast against. Asked by Heatmap News what happens if one body approves and the other does not, Mohin said he did not believe that would be the outcome, and while the thresholds for approval are set out in detail, the plan describes no procedure for what follows a failed vote.

 

READ MORE GHG Protocol and ISO to Merge Carbon Accounting Standards Into One The full announcement, the Scope 2 consultation results and the AMI multi-statement proposal

 

What is actually being combined

 

The consolidated standard will absorb four GHG Protocol workstreams and one ISO standard:

• Corporate Accounting and Reporting Standard (2004): the underlying document for Scope 1 and organisational boundaries
• Scope 2 Guidance (2015): purchased electricity, steam, heat and cooling
• Corporate Value Chain (Scope 3) Standard (2011): the fifteen upstream and downstream categories
• Actions and Market Instruments workstream: launched in 2024, no published standard yet
• ISO 14064-1:2018: organisation-level quantification and reporting

 

The standard development plan released alongside the announcement calls the result Corporate Standard Version 3.0 and splits it in two. Part one covers general requirements and the physical greenhouse gas inventory. Part two covers actions and market instruments. The plan states that either part may be subdivided further.

One line in that document deserves more attention than it has had, because the implementation guidance is expected to be published after the consolidated standard itself, on timelines the plan lists as still to be determined. That deferred guidance is not a minor appendix, since it comprises a new Corporate Standard Guidance, version 2.0 of both the Scope 2 and Scope 3 guidance, and a first Actions and Market Instruments guidance. Standards carry the requirements, while guidance carries the worked examples, the allocation rules and the answers to the questions preparers actually have. If the standard lands in Q4 2028 and its guidance follows at an unnamed later date, the practical clarity companies are waiting for arrives after the headline date, not on it.

Read the publication dates in that list again. The document governing corporate carbon accounting is twenty-two years old. The Scope 3 Standard is fifteen and has never been formally revised. This is the first structural rewrite of corporate emissions accounting since 2011, not a version bump.

A parallel piece of work sits alongside it. A joint working group is merging ISO 14067 with the GHG Protocol Product Life Cycle Standard into a single product-level standard, partly to support carbon border adjustment mechanisms. The GHG Protocol received more than 450 applications from over 50 countries for places on that group, which met in mid-July 2026, though no timeline for the resulting standard has been published.

 

Why companies have needed two approaches

 

ISO 14064-1 and the GHG Protocol Corporate Standard cover the same territory. Both define organisational boundaries, both require inventories built on accuracy, completeness, consistency and transparency, and ISO 14064-1’s content was itself derived from the GHG Protocol. The duplication between them is therefore not conceptual but operational, and it shows up in three places.

• Terminology. ISO 14064-1’s 2018 edition renamed “operational boundaries” as “reporting boundaries” and classifies indirect emissions into five categories rather than the Scope 2 and Scope 3 split most teams work in, so mapping one to the other is manual, repeated annually, and a common source of restatement.
• Assurance expectations. ISO 14064-1 is designed to be verified against ISO 14064-3 and slots into an existing ISO 14001 environmental management system, which is why organisations already running certified management systems tend to default to it.
• Access. Every GHG Protocol standard is a free download, while ISO 14064-1:2018 costs CHF 196 a copy from the ISO store.

 

Regulation then pulls in both directions, because California’s SB 253 requires emissions reporting in conformance with the GHG Protocol, with the first Scope 1 and 2 filings now due 10 November 2026 after CARB deferred the original August deadline. The ESRS application guidance for E1 tells preparers they shall consider the GHG Protocol and can also consider ISO 14064. A multinational with an ISO-certified subsidiary in Asia and a California filing obligation therefore ends up running two vocabularies across one dataset, which is the duplication the consolidation removes.

 

RELATED EVENT Reuters Sustainability Europe 2026 London, 20–21 October 2026 · 400+ sustainability, finance and procurement leaders on regulatory uncertainty and Scope 3 data

 

The difficult questions have not disappeared

 

Scope 2 is where this gets tested, and the results published on 29 July should temper expectations.

The consultation ran from 20 October 2025 to 31 January 2026 and drew close to 1,100 responses from 56 countries. On the proposal to require hourly matching of contractual instruments for large organisations, 70 per cent of the 909 respondents who answered gave little or no support and 22 per cent were in favour. On deliverability, which would require clean generation to be plausibly deliverable to the point of consumption, 59 per cent of 875 respondents were opposed and 30 per cent supportive.

Companies, industry groups and consultants made up 62 per cent of respondents, against 13 per cent from NGOs and academia. It is tempting to read the result as capture, and tempting is not the same as correct. The GHG Protocol’s own summary records that NGOs and academia were split on hourly matching, and that NGOs, government institutions, reporting programmes, academics, consultants and data providers all showed plurality support for deliverability. The disagreement runs deeper than cost. One camp holds that the market-based method allocates procurement decisions and therefore needs no physical link to consumption. The other holds that a claim to use clean electricity should track when and where that electricity was generated, or it finances nothing that would not have been built anyway.

In July, the Independent Standards Board declined to choose. It asked the technical working group to develop multiple market-based reporting approaches reflecting different theories of change, and that group reconvenes in person in September.

That is the most consequential line in the entire announcement, and it has been reported as a footnote. A standard that ships with more than one permitted market-based method is not a common global language for emissions accounting. It is a harmonised container holding an unresolved argument, and comparability between two companies on the same grid will depend on which method each selected. Plan for that outcome, because it is now the likeliest one.

Two further questions remain open and deserve to be asked publicly before Q2 2027. Neither organisation has said what the co-branded standard will cost; free access has been central to the GHG Protocol’s reach, and CHF 196 is not a rounding error for a supplier in an emerging market being asked for product-level data. And the two bodies operate on different transparency settings. The GHG Protocol publishes its working group membership and most meeting minutes. ISO does not name its technical committee experts, and Heatmap has reported that minutes of the joint product working group will be held on ISO’s non-public repository, with only summaries shared.

There is also a competitor. Carbon Measures, launched in October 2025 with ExxonMobil, BASF, Nucor, Mitsubishi Heavy Industries and Global Infrastructure Partners among its founding members, promotes product-level accounting that passes emissions liability down the value chain to customers. Its members describe it as complementary; NewClimate Institute and the Columbia Center on Sustainable Investment have called it a distraction from Scope 3 responsibility. Either way, its existence puts a clock on the consolidation. A harmonisation process that takes until 2029 to bind leaves a long window for an alternative to establish itself.

 

What different business functions should prepare for

 

• Sustainability teams. Boundary definitions and emission categories will change even where the underlying numbers do not. Budget for a mapping exercise and a restatement of at least one base year.
• Finance and audit. SB 253 limited assurance begins in 2027. A standard built alongside ISO’s verification family will raise expectations for internal controls, data traceability and evidence retention well before 2028.
• Procurement. The product-level standard, not the corporate one, is what will reach suppliers. Questionnaires, product carbon footprints and CBAM-adjacent data requests all sit downstream of it.
• Energy teams. Power purchase agreements signed this year will be assessed against criteria that do not yet exist. A legacy clause for existing contracts drew broad support in the consultation, but consultation support is not a rule.
• Software providers and their buyers. Configurable methodologies, method-level audit trails and the ability to run two market-based calculations in parallel move from nice-to-have to procurement criteria.

 

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Five things worth doing before the consultation opens

 

• Map where each standard is used today, entity by entity and report by report. Most groups do not actually know which subsidiaries report under ISO 14064-1 and which under the GHG Protocol.
• Document methodological choices while the reasoning is still fresh. An inventory management plan written in 2026 is evidence in 2029; one reconstructed in 2029 is guesswork.
• Preserve calculation histories, inputs and emission factors, not only reported totals. Restatement is a data problem before it is a methodology problem.
• Avoid hard-coding reporting systems around a single Scope 2 outcome. Multiple permitted approaches are now the probable design.
• Prepare to respond to the Q2 2027 consultation, and bring an operational view rather than a lobbying position. The last round was answered overwhelmingly by preparers, and the standard-setters noticed.