CBAM and Your Supply Chain: How to Get Emissions Data From Overseas Suppliers

Last updated: 30 June 2026*

The central compliance challenge for UK and EU importers facing CBAM is not registration, not certificate purchasing, and not understanding the regulatory framework in outline. It is a more immediate and practical problem: getting usable, accurate, verified emissions data from overseas suppliers who have no direct legal obligation to provide it, no domestic carbon pricing regime to align with, and frequently no established infrastructure for monitoring production-level greenhouse gas emissions.

Both the EU CBAM — now in its definitive phase from 1 January 2026 — and the UK CBAM launching 1 January 2027 are built on a foundational assumption: that importers can obtain installation-level embedded carbon data from their overseas producers. That assumption breaks down across much of the global supply base. Suppliers in China, India, Turkey, Egypt, and other major exporting nations operate in jurisdictions with no mandatory product-level carbon monitoring.

Asking a steel mill in Jiangsu province or a fertiliser producer in Odisha to report greenhouse gas intensity per tonne of product, in a format validated to EU or UK methodological standards, and verified by an accredited third party, is a request of significant technical complexity — and one they have no direct regulatory incentive to satisfy.

This article sets out exactly what data the regulations require, why the default value fallback is a costly one, what structural barriers compliance teams will encounter in supplier engagement, and what actions should be under way now.

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What CBAM Actually Requires From Overseas Suppliers

Both regimes require importers to declare the embedded greenhouse gas emissions in imported goods. The liability flows directly from those emission figures — but the regulations do not accept any emissions estimate. They require specific data, calculated to a defined methodology, at the level of the individual production installation.

EU CBAM: Verified Actual Data Mandatory From 2026

Under Regulation (EU) 2023/956, as amended by Regulation (EU) 2025/2083 (in force October 2025), EU importers must submit an annual CBAM declaration. The first declaration — covering goods imported during calendar year 2026 — is due by 30 September 2027.

Actual emissions data must be verified by an accredited third-party verifier before it can be used in the annual declaration. This verification requirement became mandatory for the definitive phase from 1 January 2026. During the transitional period (October 2023 to December 2025), unverified data and equivalent methods were permitted under defined conditions. That flexibility is closed.

What this means operationally: the overseas supplier must have monitored their production process using the EU methodology set out in Commission Implementing Regulation (EU) 2025/2547, had that data reviewed by an accredited verifier, and be prepared to share the resulting verified figures before the importer's declaration deadline.

The EU methodology defines specific system boundaries, greenhouse gas scope (CO₂ for most sectors; additionally N₂O for fertilisers; perfluorocarbons for aluminium), and calculation rules that do not align with domestic GHG accounting standards in most third countries or with widely-used protocols such as the GHG Protocol. A supplier with sophisticated sustainability reporting under established international standards cannot export their existing data directly into a CBAM declaration — they must recalculate using the EU's prescribed rules.

For complex goods — such as certain steel products where the final product incorporates precursor materials that are themselves CBAM goods — the data requirement extends up the supply chain. Emissions embedded in precursor materials must be separately accounted for, and where actual data is used for those precursors, separately verified.

UK CBAM: Actual Data Incentivised From Day One, No Transitional Period

The UK CBAM, established under the Finance Act 2026, takes effect from 1 January 2027 with no transitional reporting period. UK importers self-assess their liability and submit directly to HMRC. The first accounting period runs 1 January to 31 December 2027, with the return and payment due by 31 May 2028.

Under HMRC's draft secondary legislation — published February and April 2026, with a technical consultation closing 21 May 2026 — actual emissions data must be verified by a body accredited by an International Accreditation Forum (IAF) member such as the United Kingdom Accreditation Service (UKAS). Overseas accreditation bodies and verifiers are also within scope where overseas producers choose to have their data verified to UK standards.

For 2027, the UK CBAM will operate with a single default emissions value per commodity code with no country-of-origin differentiation. The feasibility of country-differentiated defaults is to be examined for years after 2027. Default values can be used for precursor goods even where actual data is used for the final product, but not the reverse: if default values apply to the final product, actual data cannot be used for precursors.

Side-by-Side: What Each Regime Requires

Requirement	EU CBAM	UK CBAM
Data type	Installation-level actual emissions (verified) or default values	Installation-level actual emissions (verified) or default values
Verification mandatory?	Yes — from 1 January 2026	Yes — from 1 January 2027
Verifier accreditation	IAF-member body; EU Delegated Regulation (November 2025)	Full member of Global Accreditation Cooperation Incorporated (Global ACI) under ISO Standards 17011:2017, 17029:2019 and 14065:2020 — per The Carbon Border Adjustment Mechanism (Emissions and Verification) Regulations 2026, page 7, point 13
Default values	Country- and product-specific; set in IR 2025/2621	Single value per CN code for 2027; no country differentiation initially
Indirect emissions (electricity)	In scope from 2026	Deferred to 2029 at earliest
Precursor data	Required for complex goods	Required; rules being finalised in secondary legislation
Greenhouse gases	CO₂; N₂O (fertilisers); PFCs (aluminium)	CO₂ across sectors; N₂O for fertilisers; PFCs for aluminium
Calculation methodology	IR 2025/2547	UK methodology in secondary legislation (being finalised)
First declaration deadline	30 September 2027 (covering 2026 imports)	31 May 2028 (covering 2027 imports)
Supplier portal available?	Yes — O3CI portal (voluntary, live since 31 December 2024)	No equivalent announced

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Why Default Values Are Not a Neutral Option

Both regimes are constructed so that default values carry a financial penalty above actual emissions. They are not neutral estimates. Default values are deliberately set at the upper range of emissions intensity for each product category, with an explicit markup to create a financial incentive for importers to obtain actual supplier data.

Under EU CBAM, default values published in Commission Implementing Regulation (EU) 2025/2621 carry a phased markup:

Year	EU CBAM Default Value Markup	Effect on Certificate Cost
2026	+10% above base default	Inflated costs begin; actual data clearly preferable for cleaner producers
2027	+20% above base default	Cost gap between actual and default widens materially
2028 onwards	+30% above base default	Full penalty rate; reliance on defaults becomes increasingly expensive

The financial consequence of this escalation is not abstract. For a large-volume importer of steel or aluminium relying on defaults across their portfolio, the difference between actual and default cost exposure can reach hundreds of thousands of euros per year on a single product line.

Analysis of fertiliser imports illustrates the scale: a 10,000-tonne urea shipment at default values could face approximately €430,000 in CBAM certificate costs, where verified actual data from a modern, gas-fed plant with N₂O abatement could reduce that figure by 40–50 per cent.

For UK importers, HMRC's policy summary confirms default values will be available and that many importers will rely on them in the early period. The policy design, however, characterises defaults as a fallback, not a steady-state approach. As UK ETS prices rise and indirect emissions enter scope from 2029 at the earliest, the financial argument for obtaining actual supplier data strengthens considerably.

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The Data Your Suppliers Must Provide

The European Commission has published the CBAM Communication Template for Installations — a standardised data collection template designed to facilitate the exchange of emissions information between non-EU producers and EU declarants. Use of the template is voluntary, but it covers all data elements required under the CBAM legislation and represents the most reliable framework for structuring supplier data requests.

The table below sets out the core data categories importers need from suppliers under the EU CBAM, with notes on UK CBAM applicability:

Data Category	Description	EU CBAM Required?	UK CBAM (2027)
Direct embedded emissions (SEE direct)	Specific direct GHG emissions per tonne of product at installation level (tCO₂e/t)	Yes	Yes
Indirect embedded emissions (SEE indirect)	Emissions from electricity consumed in production, based on applicable electricity emission factor	Yes	Deferred to 2029 at earliest
Embedded electricity	Electricity consumed per tonne of product (MWh/t)	Yes (for indirect calculation)	Not required until 2029
Production route	Specific process used (e.g. blast furnace, electric arc furnace, Haber-Bosch)	Yes	Yes — affects applicable default
Installation identification	Name, location, and operator details of the producing facility	Yes	Yes
CN code(s) of goods produced	Commodity codes of CBAM-covered goods at the installation	Yes	Yes
Reporting period	Calendar year for which data applies	Yes	Yes
Precursor data	Embedded emissions from input materials that are themselves CBAM goods	Yes (for complex goods)	Yes (rules being finalised)
Verification statement	Statement from a verifier accredited under Global ACI full membership (ISO 17011:2017, 17029:2019 and 14065:2020) confirming methodology compliance — UK CBAM requirement per The Carbon Border Adjustment Mechanism (Emissions and Verification) Regulations 2026	Yes — mandatory from 2026	Yes — mandatory from 2027
Carbon price evidence	Documentation of carbon price already paid in country of origin under eligible instrument	Where applicable	Where applicable

Suppliers are not legally required to use the EU Communication Template — they can provide data in other formats provided the underlying figures satisfy the regulatory requirements. Some producers prefer to supply data directly without the template to protect commercially sensitive process information. This is permissible under the regulation, but it places additional burden on the importer to ensure the data received maps correctly to the required fields.

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Structural Barriers to Getting the Data

The practical difficulty of CBAM supplier data collection is not simply a matter of sending a data request form. Several structural barriers compound the challenge in ways that a standard procurement or compliance process cannot easily resolve.

No Direct Legal Obligation on the Supplier

Neither the EU CBAM nor the UK CBAM places any direct regulatory duty on the overseas producer. The legal liability sits entirely with the EU or UK importer. A supplier who does not provide data faces no fine, no penalty, and no direct regulatory consequence. Their motivation to assist is commercial — the risk of losing business if the importer switches to a cooperative supplier, or the risk that defaults make trade uneconomic. That is meaningful leverage in competitive markets, but it is not the same as a regulatory obligation.

This asymmetry creates real friction, particularly for suppliers who receive data requests from multiple EU and UK customers, each presenting different templates and different levels of technical guidance, for a compliance obligation they do not formally share.

The EU Methodology Is Not the Global Standard

The EU CBAM calculation methodology defined in IR 2025/2547 does not align with the GHG Protocol, with national GHG inventory methods, or with Environmental Product Declarations or Product Carbon Footprint calculations. Even a supplier with mature sustainability reporting under ISO 14064 or the GHG Protocol cannot directly export their existing figures into a CBAM declaration. The system boundaries, allocation rules, and greenhouse gas scope differ.

For suppliers exporting to both the EU and the UK, this may mean operating two distinct calculation frameworks simultaneously — the EU methodology and whatever UK methodology is finalised in HMRC secondary legislation.

Third-Party Verification Adds Cost and Lead Time

Accredited verification is not a paperwork exercise. A qualified verifier must review the supplier's monitoring methodology, examine production records, and — in many cases — conduct a site inspection. For a supplier new to this process, the preparation phase alone is substantial.

Finding an accredited IAF-member verifier in markets such as India, Turkey, or Egypt adds further complexity. The cost falls on the overseas producer if they self-fund verification, or on the importer if they choose to support supplier verification as part of a commercial arrangement to reduce their certificate exposure. Either way, it adds cost and lead time that is absent when default values are applied.

Complex Goods Require Multi-Tier Data

For complex manufactured goods — certain steel products, aluminium alloys, and compound fertilisers — the data requirement is not satisfied by a single installation's figures. Embedded emissions from precursor materials must be accounted for, potentially across multiple countries and production technologies.

A steel product fabricator sourcing hot-rolled coil from a blast furnace operator, which in turn sources iron ore and coke from separate suppliers, faces a data aggregation challenge that can span multiple tiers of the supply chain. As the IISD has observed, calculating embedded emissions across multi-tier, multi-country supply chains poses significant and recurring challenges for data collection, verification, and consistency.

The O3CI Portal: What It Does and Does Not Solve

The EU's Operators of Third Country Installations (O3CI) portal — live since 31 December 2024 — allows non-EU installation operators to register, upload emissions data, and share it securely with specific EU declarants via EORI number. It replaces bilateral email exchange between individual importers and suppliers with a centralised platform where a supplier uploads once and shares selectively. That is a meaningful operational improvement.

However, the portal's limitations are equally important:

O3CI Portal Feature	Status
Registration as an EU CBAM operator	Available — voluntary
Upload of installation and emissions data	Available — voluntary
Secure sharing with specific EU declarants via EORI	Available
Third-party verification upload	Available from 2026
CBAM emissions calculations	Not available — portal does not perform calculations
Precursor data from upstream suppliers	Limited functionality for complex multi-tier chains
Equivalent UK portal	Not announced at time of publication

Use of the O3CI portal is voluntary. It does not reduce the underlying monitoring and calculation effort required of the supplier — it only simplifies transmission once that work is completed. For the majority of the global supply base that has not yet established CBAM-methodology monitoring at the installation level, the portal's existence does not advance compliance readiness.

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A Tiered Supplier Engagement Strategy

A uniform approach — sending the same data request to every supplier simultaneously — will not be effective. Compliance teams managing material CBAM exposure should operate a tiered engagement strategy based on the financial materiality of each supplier relationship and the realistic capacity of each supplier to respond.

Tier	Criteria	Recommended Approach	Target Outcome
Tier 1 — High-value, high-exposure	Suppliers whose goods generate the largest CBAM liability in your portfolio; cost gap between actual and default is greatest	Direct senior commercial engagement; data provision framed as a condition of the trading relationship; consider co-funding verification costs if financially justified	Verified actual emissions data by first declaration cycle
Tier 2 — Mid-volume with data capacity	Suppliers in jurisdictions with existing carbon pricing infrastructure (South Korea, EU, Canada, Brazil); producers with ISO 14064 or equivalent monitoring	Structured technical support via EU Communication Template; guidance on methodology alignment; joint verification planning	Verified actual emissions data within 6–12 months
Tier 3 — Lower-volume or limited capacity	Suppliers where CBAM exposure is lower or where the producer lacks monitoring infrastructure	Document engagement attempts; apply default values as interim position; set a longer timeline for data development	Default values short-term; actual data over a 12–24 month runway

The critical requirement for all tiers is to begin now. For UK importers, the period between mid-2026 and 31 December 2026 is the last meaningful window to establish data flows before the first compliance period begins. For EU importers already in the definitive phase, supplier monitoring must have been in place since 1 January 2026 to support the annual declaration due 30 September 2027.

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Sector-Specific Considerations

The data challenge is not uniform across sectors. The nature of the emissions, the complexity of the supply chain, and the sensitivity of the gap between actual and default values differ materially by product.

Sector	Key Emissions Driver	Multi-Tier Data Challenge	Actual vs Default Cost Sensitivity
Steel	Production route (blast furnace vs electric arc furnace)	High — fabricated products may involve multiple upstream producers	High — EAF steel can be significantly below blast furnace defaults
Aluminium	Electricity emission factor at the smelter; primary vs secondary production	Moderate for primary; lower for secondary scrap-based production	High — electricity source determines indirect emissions materially
Fertilisers	N₂O emissions; presence or absence of abatement technology	Lower — typically single-installation production	Very high — abatement technology can reduce emissions by 40–50% vs default
Cement	Process emissions from calcination; clinker-to-cement ratio	Lower — calcination is inherent to production chemistry	Moderate — process emissions are less variable than energy-related emissions
Hydrogen	Production method (grey, blue, green)	Lower for single-process producers	High — production method determines emissions intensity dramatically

Iron and steel accounted for approximately 69 per cent of EU CBAM-covered import volumes by quantity during the transitional period, making it the sector where supplier data engagement is most operationally significant.

For aluminium, the electricity source data from the smelter is a critical and often difficult-to-obtain input for indirect emissions under EU CBAM. For fertilisers, the verified presence of N₂O abatement technology at the production installation can produce a dramatically lower CBAM liability than the applicable default value — making supplier verification commercially very high-value for this sector.

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Record-Keeping Obligations

Both regimes impose record-keeping obligations that affect how supplier data must be stored and governed. Under UK CBAM, liable persons must retain records for a minimum of six years from the date of the relevant import. These records include the embedded emissions data used in liability calculations and — where actual data is used — the full chain of supplier evidence supporting those figures: the original production monitoring records, the verifier's statement, and the importer's return.

Compliance teams cannot treat supplier data as a transient submission. The evidence chain must be preserved, structured, and auditable. Competent authorities under EU CBAM have inspection powers that include verification documentation. HMRC will have equivalent powers under UK CBAM secondary legislation.

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The Procurement Dimension

CBAM changes the commercial calculus of sourcing decisions. Suppliers who provide verified, low-emission data reduce the importer's certificate cost. In commodity markets where margins are thin, that cost differential becomes a procurement criterion, not a compliance afterthought.

The logical consequence, as financial obligations escalate through 2028 and beyond, is that emissions transparency will factor into supplier qualification. Importers who build robust supplier data infrastructure early are positioned to source preferentially from verified low-emission producers. Suppliers who invest in verified emissions monitoring and engage proactively with CBAM data requests gain a commercial advantage in markets where buyers face regulatory pressure to reduce their certificate cost exposure.

For exporters in India, Turkey, Egypt, and other major supply countries — all facing significant CBAM exposure on their EU and UK-bound exports — this dynamic is already visible in how larger European buyers are structuring purchasing requirements and supplier audits.

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Key Dates and Deadlines

Date	Obligation
1 October 2023	EU CBAM transitional phase began — quarterly reporting only, no payments
1 January 2026	EU CBAM definitive phase — financial obligations begin; third-party verification of actual data mandatory
31 December 2024	EU O3CI portal went live for non-EU installation operators
1 January 2027	UK CBAM commences — first compliance period begins with no transitional phase
30 September 2027	First EU CBAM annual declaration due (covering 2026 imports)
31 January 2028	UK CBAM registration deadline for first-year importers
31 May 2028	First UK CBAM return and payment due (covering January–December 2027)
2029 at earliest	Indirect emissions (electricity) enter UK CBAM scope
2028 onwards	EU CBAM default value markup reaches 30% — full penalty rate

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Frequently Asked Questions

What is the difference between actual emissions data and default values under CBAM?

Actual emissions data is installation-specific information derived from direct monitoring of the production process, calculated according to the EU or UK regulatory methodology and verified by an accredited third party. Default values are standardised emissions intensities set by the regulator for each product category. Under the EU CBAM, default values carry a markup — 10 per cent in 2026, rising to 30 per cent from 2028 — above the base default to create a financial incentive for importers to obtain actual data. For cleaner producers, actual data also typically reflects lower emissions than the conservative default, delivering a further cost reduction.

Are overseas suppliers legally required to provide emissions data for CBAM?

No. Neither the EU CBAM nor the UK CBAM places any direct legal obligation on the overseas producer. The legal liability rests with the EU or UK importer. Suppliers provide data on a commercial basis, motivated by the risk that non-cooperative suppliers lose business to those who can offer verified data and a lower landed cost. This asymmetry of obligation is one of the most significant structural barriers in practice.

What is the O3CI portal and do my suppliers need to use it?

The O3CI (Operators of Third Country Installations) portal is a section of the EU CBAM Registry, live from 31 December 2024. It allows non-EU installation operators to upload their emissions data and share it securely with specific EU declarants via EORI number. Use is voluntary. It simplifies data transmission but does not perform CBAM calculations and does not reduce the underlying monitoring and verification effort. There is no equivalent UK portal at the time of publication.

What verification is required for supplier emissions data?

Under the EU CBAM definitive phase (from 1 January 2026), actual emissions data must be verified by an accredited third-party verifier before use in an annual declaration. Under UK CBAM (from 1 January 2027), actual data must be verified by a body that is a full member of Global Accreditation Cooperation Incorporated (Global ACI) under ISO Standards 17011:2017, 17029:2019 and 14065:2020, as defined in The Carbon Border Adjustment Mechanism (Emissions and Verification) Regulations 2026, page 7, point 13. Default values do not require third-party verification but carry a financial penalty. The EU verifier accreditation framework is set out in a Commission delegated regulation published November 2025. UK accreditation requirements are being set out in secondary legislation.

What should I do if my supplier cannot provide verified emissions data?

Apply the applicable default value for the relevant product and country of origin, document the engagement attempt thoroughly, and use the runway before your next reporting deadline to develop a path to actual data. For high-volume supply relationships where the cost gap between actual and default is material, assess whether commercially structured data support — co-funding verification or providing technical assistance — is justified by the certificate cost saving. In some cases, sourcing decisions will need to be reviewed as financial obligations escalate.

Does the UK CBAM require the same emissions data as the EU CBAM?

The two regimes share the same underlying logic but are distinct regulatory frameworks with different methodologies. The UK CBAM covers only direct emissions from 2027, with indirect emissions deferred to 2029 at the earliest. The UK methodology is being finalised in secondary legislation. Importers should not assume that EU-verified data automatically satisfies UK CBAM requirements without verifying alignment with final HMRC guidance when published.

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References and Sources

• European Commission – Regulation (EU) 2023/956 — CBAM Basic Regulation

  Date: May 2023

  URL: eur-lex.europa.eu

• European Commission – Regulation (EU) 2025/2083 — CBAM Simplification and Strengthening Amendment

  Date: October 2025

  URL: eur-lex.europa.eu

• European Commission – Commission Implementing Regulation (EU) 2025/2621 — Default Emissions Values

  Date: December 2025

  URL: eur-lex.europa.eu

• European Commission – Commission Implementing Regulation (EU) 2025/2547 — Embedded Emissions Calculation Methodology

  Date: December 2025

  URL: eur-lex.europa.eu

• European Commission – Commission Implementing Regulation (EU) 2025/2546 — Verification Principles

  Date: December 2025

  URL: eur-lex.europa.eu

• European Commission – CBAM Registry and Reporting — O3CI Portal Guidance

  Date: January 2025

  URL: taxation-customs.ec.europa.eu

• European Commission – CBAM Communication Template for Installations

  Date: Updated 2023–2026

  URL: taxation-customs.ec.europa.eu

• European Commission – EUR-Lex CBAM Transitional Period Review Report

  Date: 2025

  URL: eur-lex.europa.eu

• HMRC / HM Treasury – Finance Act 2026 — UK CBAM Primary Legislation

  Date: 2026

  URL: parliament.uk

• HMRC – Carbon Border Adjustment Mechanism: Policy Summary

  Date: April 2026

  URL: gov.uk

• HMRC – Draft Regulations: CBAM (Emissions and Verification) — Technical Consultation

  Date: April 2026

  URL: gov.uk

• HMRC – Factsheet: Carbon Border Adjustment Mechanism

  Date: November 2025

  URL: gov.uk

• UK Government – EU Carbon Border Adjustment Mechanism — Guidance for UK Exporters

  Date: April 2026

  URL: business.gov.uk

• International Carbon Action Partnership (ICAP) – EU Adopts Simplifications of CBAM Rules Ahead of 2026

  Date: October 2025

  URL: icapcarbonaction.com

• S&P Global – EU CBAM Committee Approves Revised Default Benchmark Carbon Intensity Values

  Date: December 2025

  URL: spglobal.com

• PwC – The EU CBAM: Implications for Supply Chains

  Date: 2026

  URL: pwc.com

• IISD – EU Carbon Border Adjustment Mechanism Is Set to Get Bigger

  Date: January 2026

  URL: iisd.org

• O'Melveny – How the EU's New Default Emissions Values Under CBAM Impact US Exporters

  Date: January 2026

  URL: omm.com

• Deloitte UK – The UK CBAM: What Businesses Need to Know to Get Ready

  Date: 2025

  URL: deloitte.com

• HMRC | The Carbon Border Adjustment Mechanism (Emissions and Verification) Regulations 2026 | 2026 | assets.publishing.service.gov.uk/media/69d630e745510a54bcccad8f/The_Carbon_Border_Adjustment_Mechanism__Emissions_and_Verification.

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*Correction 30 June 2026: The verifier accreditation requirement for UK CBAM has been updated to reflect the precise definition in The Carbon Border Adjustment Mechanism (Emissions and Verification) Regulations 2026, page 7, point 13.

Disclaimer

This article is published by CBAM Journal, operated by Sekason Research Limited, for information purposes only. It does not constitute legal, financial, tax, or regulatory advice. Regulatory requirements under both the EU CBAM and UK CBAM continue to evolve; readers should verify the current position against official sources including GOV.UK, HMRC, and the European Commission CBAM portal before taking compliance decisions. Sekason Research Limited accepts no liability for actions taken or not taken on the basis of this article.

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