What corresponding adjustments under Article 6 are, how they prevent double counting, when they apply to blue carbon, and how buyers check them.
Suppose a Cambodian mangrove project restores a hectare of canopy and sells the carbon credit to a European airline. Cambodia wants that tonne to count toward its own climate pledge, since the removals happened on its territory. The airline wants the same tonne to neutralize its flight emissions. Both claims are plausible. Both cannot be true — if they were, the atmosphere would see one tonne of removal while the ledger claimed two.
The corresponding adjustment is the Paris Agreement's fix for exactly this problem: an accounting entry that moves a tonne out of the selling country's books whenever it moves into someone else's. It's the least glamorous and most consequential plumbing in international carbon accounting — and if you buy blue-carbon credits, you need to understand when it applies to you. This article explains the mechanism without the acronyms-first jargon that buries most explainers. It builds on our guides to double counting and Article 6 in blue carbon.
Under the Paris Agreement, every country reports its emissions and removals through a national inventory and tracks progress against its climate pledge, the nationally determined contribution (NDC). If a country transfers a mitigation outcome abroad — sells it — but keeps it in its own inventory count, the same tonne chases two pledges. That is double counting at the international level, distinct from (but stacking with) the registry-level double selling and double use covered in our double-counting explainer.
A corresponding adjustment is a bookkeeping entry made by the transferring country in the emissions balance it reports toward its NDC. When the country authorizes a mitigation outcome for international transfer — making it an "internationally transferred mitigation outcome," or ITMO — it agrees to:
The tonne is counted once, by the acquirer. The adjustment doesn't change what physically happened in the atmosphere; it determines whose climate ledger gets to claim it. Think of it as a foreign-exchange settlement for carbon: the value moves, the accounts are updated on both sides, and ownership is unambiguous.
Importantly, authorization is a choice the host country makes per project or activity. Many blue-carbon projects operate without any Article 6 authorization — their credits are never ITMOs, their host countries never adjust, and the credits cannot legally be counted toward another country's NDC. Whether that's a problem depends entirely on what you want to claim.
Applying an adjustment requires three things to line up:
1. Authorization. The host country issues a formal authorization, typically to the project developer, stating that the credits will be used toward another party's NDC or for "other international mitigation purposes" (a category created to cover voluntary-market and aviation uses).
2. Tracking infrastructure. Authorized credits are serialized and tracked through the Article 6 database and the international registry, interoperating with the national and private registries where the credits are actually issued, transferred and retired. The plumbing still being completed matters less than the discipline: serial numbers, transfers and retirements reconciled across systems.
3. Reporting and adjustment. In its biennial transparency report, the host country includes the authorized transfers in its "structured summary" and applies the adjustment when computing progress toward its NDC.
There's one genuinely subtle design decision buried in that last step. NDCs come in different shapes: some are single-year targets (net emissions in 2030), others span multiple years. To keep adjustments comparable, the Paris rulebook lets countries either apply adjustments every year on an indicative multi-year trajectory, or average everything and adjust in the target year. The choice is disclosed upfront in the country's accounting methodology. For credit buyers this is mostly deep plumbing, but it matters if you're assessing a host country's capacity: single-year NDCs with complicated adjustments applied in one year concentrate the accounting risk.
Here's the decision tree that actually matters for buyers.
Scenario A: compliance use toward an NDC. If a country or a covered entity needs your credit to count toward a national target — e.g., an airline under a domestic scheme counting toward national aviation emissions — the credit must be authorized and adjusted. Unadjusted credits simply don't count. This is the original Article 6 use case.
Scenario B: CORSIA aviation offsetting. The international aviation offsetting scheme requires corresponding adjustments for credits used to meet its obligations. Airlines buying blue-carbon units for CORSIA need adjustment without exception.
Scenario C: voluntary corporate claims. This is the contested middle. If a corporation voluntarily offsets emissions with an unadjusted blue-carbon credit, is that double counting? Strictly, the tonne is being claimed against the corporation's inventory and remains in the host country's NDC progress — two ledgers, one atmosphere. Many integrity initiatives now argue that high-integrity "compensation" claims should use adjusted credits, while "contribution claims" — where the buyer funds mitigation without claiming it against their own footprint — are coherent without adjustment.
The emerging practical consensus, reflected in buyer guidance and the positions of major integrity bodies, is:
Our article on Article 6 and the ocean covers the policy structure behind this; the short version is that the voluntary market is increasingly bifurcating into adjusted and unadjusted shelves, priced differently.
Coastal blue carbon raises two issues land-based credits don't face as acutely.
Not all blue carbon is in the national inventory. A country's NDC accounting only captures what its inventory captures. Mangroves, tidal marshes and seagrasses appear in inventories where countries have applied the IPCC Wetlands Supplement; many have not. If a mangrove host country doesn't inventory its mangrove carbon, what exactly is being adjusted? Registries and standards resolve this differently — some require evidence that the underlying pool is covered by the host NDC before allowing voluntary "Article 6-ready" labeling. For kelp carbon, which sits outside current inventory methods altogether, the corresponding adjustment is currently a hypothetical instrument: there's nothing in the host inventory to adjust against, which is one reason the kelp policy gap matters beyond bureaucratic completeness.
Tenure and authorization are entangled. To authorize a transfer, a government must have something like ownership of the carbon rights being transferred. In coastal zones with overlapping customary tenure, that precondition can be contentious; our piece on sea country carbon rights covers the stakes.
Corresponding adjustment status is verifiable, not a matter of trust:
If a seller can't produce the letter or the registry annotation, the credit is unadjusted — price and claim accordingly.
No. Retirement prevents a credit from being used twice in market transactions; a corresponding adjustment prevents the underlying tonne from being counted twice between countries. They're separate fixes for separate layers of double counting, covering what our double-counting explainer calls the ownership and claims dimensions.
Typically yes. Adjusted credits are scarcer, demand growing regulatory and corporate appetite, and host countries may charge for authorization. Expect a premium — and treat price parity between adjusted and unadjusted listings as a signal to look harder.
In principle yes, in practice it's project- and country-specific, and retroactive authorization can be slow. Don't buy unadjusted credits on the assumption they'll be adjusted later.
Not automatically. If the buyer makes a contribution claim — funding mitigation without netting it against their own footprint — no double claim occurs, whatever the adjustment status. The problem is claims, not accounting entries alone.
Mostly outside the adjustment conversation, since kelp carbon isn't yet in national inventories — so there's no national ledger entry to adjust. If and when inventory methods extend to macroalgae, the mechanism would apply like any other pool. Until then, honest labeling and conservative claims do the work adjustment can't.
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