CBAM Registry and O3CI operator portal: what's what
The CBAM Registry is where EU declarants file. O3CI is the free portal for non-EU operators to share data. Here's how they fit together.
Published 19/10/2026 · Facts checked on 2026-10-18
Answer box
The CBAM Registry is the EU-side system where authorised declarants register, file declarations, and surrender certificates. The O3CI operator portal is a module of the Registry that lets non-EU installation operators register for free and share emissions data with their EU declarants.
Who uses which
- EU importer / indirect customs rep → CBAM Registry.
- Non-EU installation operator → O3CI (optional).
- National competent authorities → Registry (admin side).
Is O3CI mandatory for suppliers?
No. Non-EU suppliers can share data via O3CI, or by sending the Commission’s communication template directly, or by using software like CBAMWorks. The important thing is that the data reaches the EU declarant in a form the declaration can use.
Where CBAMWorks helps
- For importers: declaration-ready exports plus a verifier-ready file.
- For suppliers: we help you prepare the numbers correctly, then export the communication template (or data compatible with O3CI, planned).