ISSB, CSRD, GRI and California SB 253 compared for US companies

These four are often listed together, but only two are frameworks in the strict sense. SB 253 is a state law that asks for emissions numbers, and CSRD is an EU directive that carries its own standards. The table is as checked on 2026-10-16.

ISSB. The ISSB issued IFRS S1 and IFRS S2 in June 2023, effective for annual periods beginning on or after January 1, 2024. Use is a matter for each jurisdiction: the IFRS Foundation's April 2026 Advisory Council update counts more than 40 that had decided to use ISSB Standards or were taking steps to introduce them as of the end of March 2026, and the United States is not on that list. The SEC stayed its own 2024 climate rule on April 4, 2024, voted on March 27, 2025 (Press Release 2025-58) to end its defense of it, and published a proposal to rescind it on June 3, 2026 (91 FR 33296). No final rescission had been adopted as of 2026-10-16.

CSRD. Directive (EU) 2026/470 (Omnibus I) has been in force since March 18, 2026. It limits reporting to undertakings above EUR 450 million of net turnover and an average number of employees above 1,000 during the financial year, and for non-EU groups it keeps the Article 40a route through an EU subsidiary above EUR 200 million or a branch, for financial years starting on or after January 1, 2028. Member states must bring the amendments into law by March 19, 2027.

GRI. The GRI Universal Standards 2021 came into effect for reporting on January 1, 2023 and help organizations of any size report their effects on the economy, the environment and people.

SB 253. CARB's regulation took effect October 12, 2026 and its first Scope 1 and Scope 2 report is due on or before November 10, 2026 for entities above $1 billion that do business in California. The SB 253 and SB 261 comparison has the full dates.

Three older names still turn up. TCFD disbanded in October 2023 and the IFRS Foundation says its recommendations are fully incorporated into the ISSB Standards. SASB Standards cover 77 industries and are now the ISSB's responsibility. The Climate Disclosure Standards Board was consolidated into the IFRS Foundation in 2022.

Materiality decides what goes in the report, so it is where the frameworks diverge most. Financial materiality asks what could reasonably be expected to affect the company's cash flows, access to finance or cost of capital. IFRS S1 uses that lens, and IFRS S2 applies it to climate.

Double materiality adds a second question: what effect the company has on people and the environment. ESRS 1 describes impact materiality (actual and potential positive and negative impacts connected with the company's business) and financial materiality (sustainability-related risks and opportunities that affect the company), and a topic is reported if it is material on either view. GRI is built around the impact view and addresses a wide audience, beyond investors.

A short illustration. A manufacturer's water use may be immaterial to its investors because the plants are in water-rich regions, yet material on an impact view because the same plants draw from a stressed aquifer used by a town. Under ISSB the topic might not be reported. Under ESRS or GRI it probably would be. SB 253 sidesteps the question for emissions: the statute asks for Scope 1 and Scope 2 outright, and CARB staff's 2027 concept would allow exclusions only where an omission could not reasonably be expected to influence users of the disclosure, with an explanation. The materiality assessment is management's judgment under every framework.

IFRS S2 requires a company to disclose absolute gross Scope 1, Scope 2 and Scope 3 emissions in metric tonnes of CO2 equivalent, measured under the GHG Protocol Corporate Standard (2004) unless a jurisdictional authority or exchange requires another method. Its Scope 2 figure is location-based, with information about any contractual instruments. The ISSB's December 2025 amendments to the emissions disclosures, effective for periods beginning on or after January 1, 2027, add reliefs for Scope 3 category 15 and for the measurement method and GWP values.

SB 253 asks for Scope 1 and Scope 2 in 2026, with Scope 3 from 2027 on a schedule CARB is writing. Staff concepts presented on July 21, 2026 would require five Scope 3 categories (purchased goods and services, fuel and energy-related activities, waste, business travel and employee commuting) and would require both location-based and market-based Scope 2.

ESRS E1 covers climate change within the topics a company finds material, and a non-EU group report under Article 40a is a group-level report. GRI leaves the choice of topic standards to the reporter.

The shared base is the GHG Protocol. That is also the part in motion. The GHG Protocol held public consultations on Scope 2 between October 20, 2025 and January 31, 2026, and its consultations page expects a draft consolidated Corporate Standard for public consultation in the second quarter of 2027. Until then, the 2004 and 2015 texts are the published ones.

Assurance is where the regimes differ most in timing, and it is the part Finbryn leaves to independent providers under every one of them. GRI's page that we checked sets no assurance rule, so a customer who asks for assured GRI reporting should name the engagement it expects.

• SB 253. The statute calls for limited assurance over Scope 1 and Scope 2 starting in 2026 and reasonable assurance from 2030, but CARB's September 1, 2026 guidance accepts the 2026 filing with or without it. Staff concepts would require limited assurance from an independent third party for reports submitted in 2027.
• CSRD. Reports carry a limited assurance opinion from a statutory auditor or another authorised firm. Omnibus I postponed the deadline for the Commission to adopt limited assurance standards to July 1, 2027 and removed the requirement to adopt reasonable assurance standards.
• ISSB. IFRS S1 and S2 set disclosure requirements. Any assurance requirement is set by the jurisdiction that adopts them.

In every case the assurance provider is independent of the company and of its preparers, and a preparer's schedules are evidence for it, never a substitute. Finbryn prepares files in which each figure traces to a source document, which is what a provider tests from.

Choosing is rarely a free choice. The useful question is who is asking, and the answer usually points to one framework.

1. A California law. If counsel confirms the company is an SB 253 reporting entity, CARB's format comes first, because that one has a legal date. Use the GHG Protocol basis and keep the methodology note.
2. A parent in an ISSB jurisdiction. The group's template governs. The US entity supplies IFRS S2 data tied to its books. See ISSB reporting support.
3. An EU subsidiary or branch. Counsel in the member state decides whether CSRD applies and from which year. The group collects ESRS data. See CSRD readiness.
4. A customer or lender. Their questionnaire names its basis, usually the GHG Protocol. Build the inventory once and answer from it.
5. No one is asking. A company reporting voluntarily can choose. ISSB suits an investor audience, GRI suits a wider stakeholder audience, and either can start from the same Scope 1 and Scope 2 inventory.

None of these requires picking a winner. Two or three can apply at once, and the data work is the same.

Most of the work is shared. A single build covers:

• Boundary. Entities and sites, with the consolidation approach (equity share, financial control or operational control). Match it to whoever files. SB 253 tests revenue and doing business entity by entity but allows parent-level filing, and IFRS S2 follows the group's reporting boundary.
• Activity data. Fuel, refrigerant, electricity and spend, tied to invoices and the general ledger.
• Factors and GWP values. A register of each factor's source, edition and vintage. EPA's January 2025 Emission Factors Hub uses IPCC AR5 values of 28 for methane and 265 for nitrous oxide, and a framework or customer may name a different vintage.
• Scope 2 on both methods. Location-based and market-based, labeled, because the GHG Protocol asks for both and SB 253's staff concepts propose both. IFRS S2 requires the location-based figure with information on contractual instruments.
• A methodology note. Estimates, exclusions and changes since the last period.

From that file, each framework takes a cut: the CARB submission, the IFRS S2 emissions schedule, the ESRS E1 data points, or the customer questionnaire. The differences are in boundary, materiality, Scope 3 scope and assurance, not in the Scope 1 and Scope 2 arithmetic. The GHG inventory page shows the arithmetic with EPA's factors.

Finbryn prepares inventories, calculations, data schedules and report drafts for management to approve. It gives no legal advice on which regime applies, because that is for counsel, and it does not provide assurance or verification, because an independent assurance provider does that. It does not submit reports on a company's behalf and never says that a report meets a framework. What it leaves behind is the same under each framework: a boundary memo, activity data schedules tied to source documents, a factor register, a methodology note, draft report sections and a data request list for the group teams that own the inputs. The ESG and climate reporting hub lists the four services and what each one delivers.