2On August 24, 2026, the European Commission published the Guidance on CBAM Verification and Accreditation for Verifiers and National Accreditation Bodies. The 141-page guidance explains how verifiers should assess monitoring plans and emissions reports for installations outside the EU during the definitive phase of CBAM, as well as the accreditation, independence and competence requirements they must meet.
The guidance covers monitoring plans, risk analysis, data sampling, site visits, materiality assessments, verification reports and verifier accreditation. Although it is not legally binding, it provides a clearer picture of how the EU expects CBAM verification to be implemented.
For exporters, the message is clear:
CBAM verification is not simply a check of the final emissions figure. It is a systematic examination of production boundaries, accounting methods, measuring instruments, source data, supply-chain information and internal controls. Whether a company’s actual emissions data will be accepted by the EU depends not merely on submitting an operator’s emissions report, but on whether the complete evidence chain behind that report can withstand verification.
01 Why Has the EU Issued Dedicated CBAM Verification Guidance?
CBAM has moved beyond transitional-period data reporting into its definitive phase, in which CBAM certificates must be purchased and surrendered. Embedded emissions are no longer only a disclosure figure; they directly affect the compliance cost borne by importers.
If an EU importer wants to use actual emissions data supplied by a producer outside the EU, those data must comply with CBAM calculation rules and be verified by a suitably qualified verifier. For the same goods, the use of actual data rather than default values may produce a materially different compliance cost. The EU therefore needs a consistent answer to a practical question: what makes company-submitted actual emissions data truthful, complete and suitable for compliance? That is the immediate reason for the guidance.
The European Commission states on the first page that the document is explanatory and has no legal force. Where the guidance differs from formal EU legislation, the legislation and the official text published in the Official Journal of the European Union prevail.
02 What Does CBAM Verification Actually Examine?
Many companies may assume that CBAM verification only checks whether emissions per tonne of product have been calculated correctly. The guidance makes clear that the scope goes far beyond the final result.
Verifiers are expected to examine whether:
• the company’s monitoring plan complies with the CBAM methodology;
• the monitoring and calculation methods actually used are consistent with the monitoring plan;
• the reporting-period data are complete, including installation boundaries, production processes and emission sources; precursor, direct-emissions and indirect-emissions data; and the data needed to allocate process emissions, such as heat inputs and outputs, waste-gas flows, and electricity production and consumption;
• the data are accurate, including fuel and material quantities, carbon content, emission factors, net calorific values, biomass fractions, heat and electricity flows, precursor quantities and the validity of related precursor verification reports;
• data-processing and calculations for embedded emissions and free allocation are correct;
• the company’s data-control system operates effectively; and
• the operator can provide evidence showing how its data-flow activities, control system and supporting procedures are designed and operated, and how monitoring and reporting are improved.
Verifiers may trace figures back to source records, compare internal and external data, recalculate results, perform trend analyses, conduct interviews and observe activities on site. For example, energy-purchase invoices may be reconciled with meter readings; output may be compared with design capacity, energy consumption and historical trends; and laboratory reports, calibration records, inventory ledgers and spreadsheet formulas may all be inspected.
CBAM verification therefore checks not only the result, but also the methodology, data sources and evidence chain behind it. Even where a final figure appears correct, missing source data may prevent the verifier from obtaining sufficient evidence. Incorrect boundaries or omitted emission sources may constitute non-conformities and affect the verification opinion.
03 How Is CBAM Verification Conducted?
A complete CBAM verification engagement generally includes:
• a pre-engagement assessment of scope, project risk, competence, independence and expected verification time;
• strategic analysis and risk analysis to identify areas susceptible to material misstatement;
• preparation of a verification plan, testing plan and data-sampling plan;
• process analysis through data tracing, cross-checking, recalculation, trend analysis, interviews and on-site observation;
• correction of identified misstatements and non-conformities by the operator;
• independent review of the verification work and report; and
• issuance of the verification report and opinion.
｜First, the monitoring plan is the starting point.
The guidance repeatedly describes the monitoring plan as the cornerstone or starting point of CBAM verification. It is effectively the company’s operating manual for CBAM emissions monitoring and accounting. It should explain how installations and production processes are defined; which emission sources, fuels, materials and precursors are involved; where each data item comes from; which meters and testing methods are used; how emissions are allocated to processes and products; how missing data are handled; and how data review, equipment calibration and document control are performed.
Unlike EU ETS verification, CBAM verification assesses not only whether the company followed its monitoring plan, but also whether the plan itself complies with the CBAM methodology. During a company’s first CBAM verification, the plan will generally be assessed in full. Significant changes to the installation, energy supply, production route, precursor sources or calculation method should trigger an update and may require reassessment.
｜Second, physical site visits are generally indispensable.
Site visits are used to confirm that installation and production-process boundaries match the monitoring plan; emission sources, material flows and technical connections are complete; measuring instruments exist and operate properly; monitoring and internal-control procedures are implemented in practice; and documents are consistent with actual site conditions.
Under strict conditions, a physical site visit may be replaced by a virtual visit or waived in a particular year. For example, where a physical visit was performed in the previous reporting period, no material changes have occurred, the verifier understands the monitoring and reporting system, and all necessary evidence can be obtained remotely, a virtual visit may be possible in the following year. Where physical visits were completed in each of the two preceding periods and other risk controls are met, a visit may be waived in the third year.
The guidance gives two typical sequences: physical in year one, virtual in year two and physical in year three; or physical in years one and two, followed by a waiver in year three. Virtual visits and waivers cannot be combined. If remote procedures do not produce sufficient evidence, a physical visit is still required. For Chinese producers undergoing CBAM verification for the first time, on-site verification will therefore usually be difficult to avoid.
｜Third, precursor data may become a major verification challenge.
For complex goods, embedded emissions include both the attributed emissions of the production process and the embedded emissions carried by relevant precursors. If a company wants to use actual emissions data for purchased precursors, the verifier must confirm that the precursor producer has supplied a verification report for the corresponding production year; the report contains a positive opinion; the issuing verifier held valid CBAM accreditation at the time; the accreditation scope covers the relevant sector; and the data used by the company exactly match the precursor verification report.
If these points cannot be demonstrated or corrected before verification is completed, the verifier will require the relevant actual precursor data to be replaced with EU default values. Precursors of the same type from different producers, countries or production years should in principle be combined using a quantity-weighted average. Assigning a particular source to a specific production process requires sufficient logistics and management evidence.
Verification is therefore extending upstream through precursor supply chains. Even if a downstream company’s own data are complete, untraceable precursor sources or the absence of a valid report matching the installation, year and product may force the use of EU default values.
｜Fourth, the verification outcome determines whether actual data may be used.
The guidance describes four broad outcomes:
(1) Satisfactory verification: no material misstatement is present and a positive opinion may be issued. A report with no issues is issued without comments; one containing non-material misstatements, non-material non-conformities or improvement recommendations may be issued with comments.
(2) Uncorrected material misstatement: if the operator fails to correct it before the report is issued, the verifier provides a negative opinion.
(3) Limitation of scope: where key source data are missing, the monitoring plan is incomplete or the operator fails to provide sufficient information, the verifier cannot obtain the necessary evidence and the result is negative.
(4) Inability to obtain reasonable assurance: where issues such as uncalibrated equipment or missing controls create substantial uncertainty and additional testing still cannot establish that the report is free from material misstatement, a negative opinion is also issued.
Once a negative opinion is issued, the actual data concerned cannot be used for CBAM reporting. The authorised CBAM declarant or downstream producer must instead use default values. The immediate consequence is therefore not simply a need for corrective action: actual emissions data lose their eligibility for use, potentially increasing compliance cost and affecting customers’ sourcing decisions.
｜Fifth, verification must be planned well in advance.
The reporting period for a CBAM installation emissions report is the calendar year, from January 1 to December 31. Final verification cannot be completed before the reporting year ends, but companies should not wait until the following year to begin preparing.
The guidance recommends engaging a verifier early in the reporting year so that monitoring-plan assessment, strategic analysis, risk analysis and some on-site work can begin in advance. Authorised CBAM declarants must submit the annual CBAM declaration by September 30 of the following year. Because importers must consolidate data across products and suppliers, complete internal quality reviews and purchase CBAM certificates, the guidance notes that they will generally seek to receive verification reports by mid-August at the latest.
Mid-August is not a statutory verification deadline; it is a practical recommendation linked to the September 30 filing deadline. For complex goods involving precursors, the timetable may be even tighter because upstream precursors must be verified before downstream products can use their actual emissions data.
Companies planning to use actual data for purchased precursors should contact suppliers early, confirm when data and verification reports will be delivered, and set a clear internal cut-off date—for example, the end of May. If a valid report matching the precursor installation, production year and product is still unavailable by that date, the company may need to use the corresponding EU default value for the reporting period to avoid delaying its own verification.
04 What Should Exporters Do Now?
Companies can begin preparing in at least four areas.
｜1. Establish a CBAM-compliant monitoring plan as soon as possible
Define installation boundaries, production processes, emission sources, precursors, measuring instruments, calculation methods, data flows and control procedures. A monitoring plan should not be a one-off document prepared for verification; it should be embedded in day-to-day production and data management, with clear responsibilities for collection, review and corrective action.
｜2. Conduct a verification gap analysis in advance
Review source records, measuring instruments, calibration records, inventory management, calculation formulas and document versions using the logic of a future formal verification. Where data gaps are identified, determine alternative sources and calculation methods under the monitoring plan and retain a complete calculation trail and supporting evidence.
｜3. Integrate precursor management into supply-chain management
Identify which purchased materials are CBAM precursors and confirm actual emissions data, production years, installation information and verification arrangements with suppliers. It is not enough to obtain a report containing an emissions figure; the company must be able to obtain a valid verification report corresponding to the specific installation, year and product.
｜4. Define the boundary between consulting and verification responsibilities early
Building a CBAM accounting system and conducting independent third-party verification require appropriate separation of responsibilities. Companies should clarify each party’s role at the start of the project to avoid conflicts of interest that could prevent completed accounting or verification work from being recognised by the EU.
What companies need for CBAM is not a temporary emissions spreadsheet, but a carbon-data management system that operates continuously, traces figures back to source documents and withstands on-site verification. Drawing on its global mainstream databases and localised emission-factor library, Carbonstop provides end-to-end CBAM services covering monitoring-plan preparation, data collection and governance, embedded-emissions accounting, verification gap analysis, report generation and third-party compliance support. These services help companies in steel, aluminium, cement, fertilisers and other sectors identify data risks early and reduce the risk of being forced to use default values because of missing precursor information, non-compliant methods or an incomplete evidence chain.
Carbonstop is also developing a carbon-management self-assessment tool to help companies understand their current foundation and identify gaps. More detailed guidance will be released when the tool becomes available.
Note: This article is based on the European Commission’s Guidance on CBAM Verification and Accreditation for Verifiers and National Accreditation Bodies, published on August 24, 2026. The guidance is explanatory and not legally binding. Specific requirements concerning CBAM accounting, verification, accreditation, default values and annual declarations are governed by formal EU legislation, texts published in the Official Journal of the European Union and the latest guidance from the competent authorities.
