On 17 December 2025, the European Commission (EU) published a set of provisionally documented draft acts for consultation, with the objective of finalising the detailed rules governing the definitive phase of the Carbon Border Adjustment Mechanism (CBAM), which will apply from 1 January 2026. These documents include draft implementing acts, technical guidance on methodologies for calculating embedded emissions, and emission factors applicable to goods within the scope of CBAM.
Although these drafts do not yet constitute legally binding final legislation, they provide a reliable indication of how CBAM will operate in practice during the definitive phase. For non-EU operators, including manufacturers in Vietnam, this period represents a critical transition from the transitional reporting period to a full compliance regime involving the purchase and surrender of CBAM certificates.
The following sections highlight the key elements that companies should prioritise when preparing their CBAM compliance strategies.
During the definitive phase, the EU will publish default values for embedded emissions by CN code and product category, differentiated by country of origin. These default values may only be applied where the producer is unable to provide verified actual embedded emissions at installation level.
Importantly, for CBAM goods other than electricity, default values will be subject to an upward adjustment (mark-up). This policy design serves to:
As a result, reliance on default values generally leads to higher declared embedded emissions and therefore a higher number of CBAM certificates to be surrendered. For installations with relatively low greenhouse gas (GHG) intensity, early investment in MRV systems can substantially reduce long-term CBAM compliance costs.
From 2026 onwards, all actual embedded emissions used for CBAM declarations must be verified by an accredited verifier. This represents a fundamental departure from the transitional period, during which reporting was largely informational.
Companies will be required to prepare a comprehensive emissions documentation package, consisting of the following core components:
Operator’s Emission Report is prepared by the non-EU installation and quantifies the embedded emissions of CBAM goods based on installation-level activity data and measurements or calculations. It constitutes the primary source document for verification and for CBAM declarations submitted by the EU importer.
This marks a shift away from the use of the Communication Template (Excel format) applied during the transitional period. Instead, producers must compile a structured OER, supported by transparent calculation files and auditable data sources.
While the draft acts do not prescribe a single mandatory template, they define in the annexs about the minimum content framework that must be met for CBAM purposes.
This document provides a concise overview of the key parameters derived from the OER, facilitating efficient data exchange with the authorised CBAM declarant and reducing iterative clarification requests.
Although it cannot replace the OER, this summary is strongly recommended in practice, as it allows EU importers to rapidly assess scope, system boundaries, assumptions, and material data sources before engaging with the full documentation set.
These documents describe how embedded emissions are monitored and calculated, including: installation and system boundaries; production routes and relevant processes; emission sources; calculation-based or measurement-based methodologies; activity data collection procedures; data quality assurance and control (QA/QC); treatment of data gaps; and measures to prevent double counting of emissions, etc.
The monitoring plan functions as the installation’s emissions management framework, while the monitoring report presents period-specific results derived from that plan.
The draft acts explicitly require that documentation be sufficiently detailed to allow a verifier to trace calculations, reproduce results, and assess data reliability. In practice, this documentation forms the backbone of a GHG management system, supporting not only CBAM compliance but also broader decarbonisation, ESG, and supply-chain transparency objectives.
Where a producer supplies CBAM goods to multiple EU importers, the draft rules allow and encourage the preparation of declarant-specific addenda.
This approach limits the disclosure of commercially sensitive or personal data to only the relevant authorised CBAM declarant. These addenda may be submitted as annexes for verification purposes and used solely to demonstrate compliance with the CBAM obligations of the specific importer concerned.
According to the draft provisions, embedded emissions associated with precursors used in the production of CBAM goods must be included in the total embedded emissions.
Operators may choose between:
Where the actual data are used, producers must demonstrate full traceability, transparency, and third-party verification information, including ones about the origin of precursors, production periods, emission determination methodologies, and valid verification statements. Failure to meet these requirements will result in default values being applied.
Under CBAM, the EU importer bears primary legal responsibility for compliance. Where imports of CBAM goods exceed 50 tonnes, the importer must obtain the status of an authorised CBAM declarant.
Non-EU producers, including those in Vietnam, do not submit data directly to the CBAM Registry. Instead, they provide verified embedded emissions data and supporting documentation to EU importers and cooperate with accredited verifiers throughout the verification process. Based on this information, the authorised CBAM declarant submits the CBAM declaration and purchases and surrenders CBAM certificates corresponding to the declared embedded emissions.
For verification, the draft rules require a mandatory on-site visit in the first year of verification. In subsequent years, verification may be conducted remotely or without a site visit under specific conditions; however, at least one on-site visit is required every two years.
From 2026 onwards, the price of CBAM certificates will be linked to the quarterly average reference price of allowances under the EU Emissions Trading System (EU ETS). While EU importers are responsible for purchasing and surrendering certificates, the associated costs may be contractually shared with non-EU producers through commercial agreements.
Message from GreenCIC
From 1 January 2026, CBAM will move decisively beyond a reporting obligation and become a real carbon cost at the EU border. For exporters, this is not only a compliance challenge—it is also a strategic turning point. Companies that prepare early will be able to control CBAM costs, strengthen their negotiating position with EU buyers, and protect long-term market access, while those that delay risk higher carbon charges, reduced competitiveness, and loss of commercial opportunities.
GreenCIC partners with Vietnamese enterprises to turn CBAM compliance into a competitive advantage. With a deep understanding of CBAM rules, EU ETS linkages, and practical implementation at installation level, we support companies in moving from uncertainty to readiness with confidence. Our CBAM advisory services include:
Analysis and compilation – GreenCIC, December 2025
greencic@greencic.vn
