Carbon Border Adjustment Mechanism (CBAM) — Definition and GHG Accounting Context
For two decades the EU gave carbon-intensive industries free Emissions Trading System allowances to stop them relocating production to countries with no carbon price — a workaround that blunted the price signal it was meant to send. CBAM is the instrument that lets the EU withdraw those free allowances without triggering the relocation it feared.
CBAM puts a carbon price on imports equal to the price a domestic producer would have paid under the EU ETS — so the carbon cost of a tonne of steel is the same whether it is made in Duisburg or imported from outside the bloc.
The Carbon Border Adjustment Mechanism (CBAM) is an EU carbon tariff that charges importers for the greenhouse gas emissions embedded in six carbon-intensive goods — iron & steel, aluminium, cement, fertilisers, hydrogen, and electricity — mirroring the carbon cost paid by EU producers under the EU Emissions Trading System. A transitional reporting phase ran 2023–2025; the definitive phase, with purchasable CBAM certificates, began in 2026.
Definition and Legal Basis
CBAM was established by Regulation (EU) 2023/956 of the European Parliament and of the Council of 10 May 2023. It is a climate measure in the form of a border levy: an importer bringing a covered good into the EU customs territory must account for the greenhouse gas emissions released during that good’s production and surrender a corresponding number of CBAM certificates, each representing one tonne of CO₂-equivalent. The certificate price is tied to the EU ETS auction price, so the border charge tracks the domestic carbon price rather than sitting apart from it.
The stated purpose is to prevent carbon leakage — the displacement of emissions (and production) to jurisdictions with weaker climate policy. As the EU withdraws the free ETS allowances that historically shielded its heavy industry from international competition, CBAM applies the equivalent cost to imports, so decarbonisation inside the bloc does not simply export the emissions abroad. The mechanism covers direct embedded emissions from the production process and, for some sectors, indirect emissions from the electricity consumed in production.
CBAM is a declarant obligation under customs and trade law, not a corporate GHG inventory line. The embedded-emissions figure an importer reports to CBAM is conceptually adjacent to a Scope 3 Category 1 (purchased goods) figure — both concern emissions embedded in purchased inputs — but the two are calculated under different rules, expressed against different boundaries, and must not be treated as interchangeable. This distinction is developed in the Common confusions section below.
CBAM answers one question: what would this import have cost in carbon if it had been produced under the EU ETS? The importer pays that difference at the border. It is a price-equalisation instrument — its job is to remove the cost advantage of importing from an uncapped jurisdiction, not to raise revenue or to measure a company’s own carbon footprint.
The Six Covered Sectors
At the start of the definitive period, CBAM applies to six carbon-intensive product groups, identified in Annex I of Regulation (EU) 2023/956 by their Combined Nomenclature (CN) codes — the EU’s customs classification. Scope is defined by CN code, not by broad sector name, so within each group only the listed goods are captured. The mechanism was deliberately launched on the sectors with the highest carbon-leakage risk and the most emissions-intensive production; the Commission is empowered to extend coverage to further goods over time.
| Sector | Example goods (CN-classified) | Direct emissions | Indirect emissions |
|---|---|---|---|
| Iron & steel | Pig iron, crude steel, flat & long products, tubes, some downstream articles (screws, bolts) | Covered | Covered |
| Aluminium | Unwrought aluminium, bars, rods, profiles, wire, plates, foil | Covered | Covered |
| Cement | Cement clinker, Portland/aluminous cements, calcined clays | Covered | Covered |
| Fertilisers | Nitric acid, ammonia, urea, nitrogenous & mixed fertilisers | Covered | Covered |
| Hydrogen | Hydrogen gas | Covered | Covered |
| Electricity | Imported electrical energy | Covered | n/a (electricity is the good) |
Sectors and goods per Annex I, Regulation (EU) 2023/956. “Direct” = process and combustion emissions at the production installation; “indirect” = emissions from electricity consumed in production. Precise scope is set by CN code — consult the current Annex I for the definitive list.
How the Charge Is Calculated
The CBAM charge for a consignment reduces to a chain of three quantities: how much was imported, how carbon-intensive its production was, and the gap between the EU carbon price and any carbon price already paid at origin.
Certificates due = Embedded emissions × (CBAM certificate price − Carbon price already paid at origin)
Embedded emissions = Quantity imported (t) × Specific embedded emissions (tCO₂e/t of good)
Two features of this chain are frequently missed. First, the origin carbon price deduction: if a verified carbon price has already been paid in the country of production, the importer deducts it, so CBAM only collects the difference up to the EU price — it is an adjustment, not a double charge. Second, the CBAM certificate price is not fixed; it is set from the EU ETS auction price, so the border cost moves with the domestic carbon market.
Worked micro-example
An importer brings 100 tonnes of crude steel into the EU and uses the applicable default specific embedded-emissions value of 2.1 tCO₂e per tonne (illustrative default; the value in force is set per country and CN code by the CBAM Implementing Regulation). No carbon price was paid at origin. Assume a CBAM certificate price of €75/tCO₂e (illustrative; the live price tracks the EU ETS auction price).
| Step | Calculation | Result |
|---|---|---|
| Embedded emissions | 100 t × 2.1 tCO₂e/t | 210 tCO₂e |
| Origin carbon price paid | — (none) | €0 |
| CBAM charge | 210 tCO₂e × €75/tCO₂e | €15,750 |
Illustrative arithmetic with hardcoded inputs — not a live quotation. The default emission factor and certificate price shown are placeholders for the mechanism; the operative values are set by the CBAM Implementing Regulation and the EU ETS market respectively. To run a declaration with current values, use the EU CBAM calculator.
Transitional vs Definitive Period
CBAM was introduced in two stages so that importers and third-country producers could build the data pipelines before any money changed hands.
A reporting-only phase. Importers of covered goods filed quarterly CBAM reports declaring the embedded emissions of their imports, but surrendered no certificates and paid no charge. The purpose was data collection and methodology familiarisation. Simplified and default-value-based reporting was permitted during this window to ease the transition.
The financial obligation begins. Importers must be authorised CBAM declarants, submit an annual CBAM declaration of verified embedded emissions, and purchase and surrender CBAM certificates to cover them. In parallel, the free EU ETS allowances for the covered sectors are phased out on a published schedule, so the CBAM obligation rises as the free-allocation cushion falls.
The reporting mechanics of both phases — quarterly transitional reports and the annual definitive declaration — are procedural rather than definitional, and are covered in the EU CBAM methodology.
Default Values vs Verified Emissions
An importer can report embedded emissions two ways, and the distinction is the single most consequential choice in a CBAM declaration.
- Verified actual emissions. The embedded-emissions figure is calculated from the third-country producer’s own installation data, following the CBAM monitoring rules, and verified. This is the preferred and, in the definitive period, generally required basis where actual data is obtainable.
- Default values. Where actual, verified data cannot be established, the importer uses default emission factors published by the Commission — set per country and CN code, and expressed in tonnes of CO₂-equivalent per tonne of good. Defaults are intentionally conservative so that they do not reward the absence of data; a producer with genuinely lower emissions is disadvantaged by falling back on a default.
CBAM default values exist for the case where verified producer data is unavailable — they are a compliance backstop, not a convenient substitute for engagement with suppliers. Because defaults are set conservatively, systematically defaulting inflates the declared embedded emissions and therefore the certificate cost. The commercial incentive runs toward obtaining verified actual data from producers, exactly as the mechanism intends. These default values are also regulatory records tied to a specific Implementing Regulation — they are not a general-purpose emission-factor set and should not be repurposed as Scope 3 factors in a corporate inventory.
CBAM and the EU ETS
CBAM cannot be understood in isolation from the EU Emissions Trading System, because it is engineered as the ETS’s mirror at the border. The ETS caps and prices the emissions of installations inside the EU; CBAM applies an equivalent price to the emissions embedded in imports of the same goods. The CBAM certificate price is derived from the ETS auction price, and the phase-out of free ETS allowances for the covered sectors is matched to the phase-in of the CBAM obligation, so that domestic producers and importers face converging carbon costs rather than a cliff edge in either direction.
The two are complementary instruments, not alternatives: the ETS handles the internal carbon price, CBAM handles the border. A full account of the trading system, allowance auctioning, and free-allocation phase-down belongs to the EU ETS reference — this page defines CBAM and links to it rather than reproducing it.
Common Confusions
- CBAM embedded emissions are not a Scope 3 factor. A CBAM declaration reports emissions embedded in imported goods under trade-law monitoring rules against a customs boundary. A Scope 3 Category 1 figure reports value-chain emissions under the GHG Protocol against an organisational boundary. They overlap in subject matter but diverge in method, boundary, and purpose — a CBAM default value dropped into a Scope 3 inventory is a category error.
- Default value ≠ actual emissions. Defaults are a conservative fallback for missing data, not a neutral estimate. Reporting on defaults typically overstates embedded emissions relative to verified actuals, raising the certificate cost — see Default values vs verified emissions above.
- EU CBAM ≠ UK CBAM. The United Kingdom is introducing its own, separate Carbon Border Adjustment Mechanism on a different timetable and with a distinct design. Goods and obligations do not transfer between the two regimes; an importer into the UK follows the UK CBAM rules, not these. This page defines the EU mechanism.
- The charge is a difference, not a gross levy. A carbon price verifiably paid in the country of production is deducted, so CBAM collects only the gap up to the EU price. Ignoring the origin-price deduction overstates the liability.
Related Terms, Standards, and Tools
Frequently Asked Questions
CBAM is an EU carbon tariff that charges importers for the greenhouse gas emissions embedded in certain carbon-intensive goods — iron & steel, aluminium, cement, fertilisers, hydrogen, and electricity. Established by Regulation (EU) 2023/956, it makes imports carry a carbon cost equivalent to the price EU producers pay under the EU Emissions Trading System, so that decarbonising EU industry does not simply push emissions and production abroad — a problem known as carbon leakage.
At the start of the definitive period, CBAM covers six sectors: iron & steel, aluminium, cement, fertilisers, hydrogen, and electricity. Coverage is defined precisely by Combined Nomenclature (CN) customs codes in Annex I of Regulation (EU) 2023/956, so within each sector only the listed goods are in scope. The European Commission can extend coverage to additional goods over time.
CBAM had two phases. The transitional period (2023–2025) was reporting-only — importers filed quarterly reports on embedded emissions but paid nothing. The definitive period began in 2026: importers must be authorised CBAM declarants, submit an annual declaration of verified embedded emissions, and purchase and surrender CBAM certificates to cover them. In parallel, free EU ETS allowances for the covered sectors are phased out on a published schedule.
The number of CBAM certificates an importer must surrender equals the embedded emissions of the goods (quantity imported × specific embedded emissions in tCO₂e per tonne) multiplied by the difference between the CBAM certificate price and any carbon price already paid in the country of production. The certificate price tracks the EU ETS auction price. If a carbon price was verifiably paid at origin, it is deducted, so CBAM collects only the gap up to the EU price. To run a declaration with current values, use the EU CBAM calculator.
No. CBAM embedded emissions are reported under trade-law monitoring rules against a customs boundary, for the purpose of calculating a border charge. A Scope 3 Category 1 figure reports value-chain emissions under the GHG Protocol against an organisational boundary, for the purpose of a corporate inventory. The two concern related subject matter — emissions embedded in purchased goods — but are calculated differently and are not interchangeable. In particular, CBAM default values are conservative regulatory fallbacks and should not be reused as Scope 3 emission factors.