On 27 August 2026, the European Commission published a 146-page manual for the Installation Operators and Accredited Verifiers Portal. Two verifier access guides followed on 28 August. The documents explain how non-EU operators, accredited verifiers and authorised declarants will exchange emissions information through the Carbon Border Adjustment Mechanism (CBAM) Registry.

The release documents the access, registration and permission sequence required before verified actual emissions can reach an authorised declarant.

The Commission calls the module the Operators of Third-Country Installations (O3CI) Portal. A non-EU producer can enter installation and annual emissions information once, then make the relevant data available to EU customers through the Registry without circulating the full underlying dataset to every importer.

Verifier registration has three stages

A verifier must first obtain CBAM accreditation from an EU national accreditation body. It then requests technical access to O3CI through EU Access. Commission approval of that request provides a working login but does not register the organisation as a verifier in the Registry.

The firm must submit a separate business-registration request inside O3CI. The national competent authority in the Member State where the verifier is accredited assesses the application. Supporting documents include the accreditation certificate, company registration and evidence that the applicant can represent the firm.

Only after that approval does the organisation appear as a registered accredited verifier. The portal also separates administrator and ordinary-user permissions: an administrator can submit registration and collaboration requests, while an ordinary user cannot complete those actions. Verifier firms therefore need an available administrator before onboarding installations.

An active collaboration controls access to installation data

A registered operator can add its installations and prepare annual emissions records covering production routes, goods, direct and indirect emissions, and any carbon price effectively paid in the country of production. The Registry applies format and plausibility checks, but a saved record is not a verified record.

The operator and verifier must establish an active collaboration in O3CI before the verifier can view the installation information. Either party may initiate the request, and the other must accept it. An engagement letter or email exchange does not create this Registry permission.

Only one verifier can have an active collaboration with an installation at a time. If the operator changes verifier, the existing collaboration must be removed before the replacement can become active. The collaboration grants access; it does not confirm that the emissions have passed verification.

The verifier must still assess the installation boundary, production routes, source data, controls and calculations. Our analysis of the Commission's CBAM verification and accreditation guidance examines those assurance requirements, including evidence, materiality and site visits.

Operators, verifiers and declarants need aligned Registry records

An authorised declarant retrieves shared operator information through the Emissions area of the CBAM Registry. The declarant must first give its Economic Operators Registration and Identification (EORI) number to the supplier outside the Registry. An operator may therefore have completed its installation record without connecting it to the correct EU customer.

The Commission expects accredited verifiers to issue the first verification reports in January 2027. The authorised declarant will need the correct verified information for the annual CBAM declaration covering 2026 imports, due by 30 September 2027.

Before verification begins, importers should confirm that each supplier can identify the installation and production route behind the imported goods. Operators should complete O3CI registration and annual records, while verifier firms should finish both technical access and business registration. The active collaboration should then be checked in the portal before evidence review starts.

The European Commission's CBAM Registry page contains the portal manual and verifier access guides.