The world’s first global compliance market for international aviation.

CORSIA is the Carbon Offsetting and Reduction Scheme for International Aviation — the first global market-based measure to address CO₂ emissions from international aviation. It was established by the International Civil Aviation Organization (ICAO), a UN specialised agency, and is codified in ICAO Annex 16, Volume IV to the Convention on International Civil Aviation. Operating in three phases (Pilot 2021–2023, First Phase 2024–2026, Second Phase 2027–2029), CORSIA requires participating airlines to monitor international CO₂ emissions, file verified Emissions Reports, and offset emissions above the 85%-of-2019 baseline by purchasing and cancelling CORSIA Eligible Emissions Units. From 2027, participation becomes mandatory for most ICAO Member States.

It depends which of the two CORSIA verifier roles is in scope. The canonical role is the operator-side verifier — the independent verification body that assesses an airline’s annual Emissions Report under ICAO Annex 16 Vol IV Chapter 3. Day-to-day work: review the airline’s Monitoring Plan, assess data sources and fuel-burn calculations, sample flights to test the reported CO₂ figures, confirm the Sectoral Growth Factor application, review the Emissions Unit Cancellation Report, and issue the Verification Report the airline submits to its State authority. The supply-side role overlaps with Verra Lead Assessor work — verifying that offset projects whose credits become CORSIA EEUs have been properly validated under their issuing programme. Othello’s bench operates both readings under Panit’s CORSIA Verifier credential, with adjacent Verra Lead Assessor credential covering the supply-side overlap.

Participation and EEU supply. Phase 1 (2024–2026) is voluntary but actively participated in — 130 ICAO Member States, eight approved EEU supply programmes, the first Emissions Unit Cancellation Report cycle covers the full three-year period. Phase 2 (2027–2029) is mandatory for most ICAO Member States — the participation switch is the key change. EEU supply tightens dramatically — only four programmes are fully approved for Phase 2 so far (American Carbon Registry, Architecture for REDD+ Transactions, Gold Standard, Verra VCS), narrowing buyer options. The 85%-of-2019 baseline persists through 2035 regardless of phase. IATA projects 146–236 million units of Phase 1 EEU demand; Phase 2 expected to grow further.

COVID-19. CORSIA’s original baseline was the average of 2019 and 2020 international aviation emissions — but the 2020 pandemic collapsed international air traffic Revenue Tonne Kilometres by roughly 60%, which would have set the baseline so low that operators would face massive offsetting obligations on what was effectively recovery growth. ICAO Assembly Resolution A42-22 reset the baseline to 85% of 2019 emissions through 2035 — a single-year anchor avoiding the pandemic distortion, set deliberately below 2019 (the 15% reduction is implicit in the “85%”). The baseline being below recent emissions is what produces a positive Sectoral Growth Factor and makes offsetting obligations commercially meaningful.

Thailand’s Premium T-VER (Thailand Voluntary Emission Reduction) programme — administered by TGO — is one of the eight ICAO-approved EEU programmes for CORSIA Phase 1. The “Premium” designation refers to a tightened set of T-VER methodologies that meet CORSIA’s Emissions Unit Eligibility Criteria, distinguishing them from standard T-VER credits used in Thai domestic markets. This is commercially significant for Thai-jurisdiction project proponents — domestic T-VER projects can be developed and verified for international airline-CORSIA buyer markets, with TGO providing the issuing-body authority and ICAO providing the procurement legibility. Othello operates both ends under Panit’s TGO CFO + CFP Auditor and CORSIA Verifier credentials. See /certifications/tgo/.

ISO 14064-3 is the technical methodology floor. ICAO Annex 16 Vol IV cross-references ISO 14064-3:2019 as the verification methodology standard, and ICAO Doc 9501 (the Environmental Technical Manual Vol IV) elaborates on how verification activities should be conducted consistent with both the ICAO Annex and the ISO methodology. A CORSIA verifier brings ICAO program-specific competence on top of ISO 14064-3 procedural discipline; Panit holds the CQI/IRCA ISO 14064 Lead Auditor credential alongside the CORSIA Verifier credential — meaning the underlying ISO competence is independently credentialled. See /certifications/iso-14064/.

The Sectoral Growth Factor (SGF) is the figure ICAO publishes annually that translates “the aviation industry’s emissions above baseline” into each operator’s offsetting obligation. Each year, ICAO calculates the SGF based on aggregate international aviation CO₂ data submitted by State authorities; airlines then apply the SGF to their own verified Emissions Report to determine how many CORSIA Eligible Emissions Units they must cancel. A positive SGF means net offsetting obligations; a negative SGF (theoretically possible if the sector contracts below baseline) means no offsetting obligation that year. Phase 1’s SGF for 2024 was the first non-zero SGF released, making the first EUCR cancellation cycle commercially material.

The Emissions Unit Cancellation Report (EUCR) is the airline’s evidence to its State authority that it has cancelled enough CORSIA Eligible Emissions Units to discharge its offsetting obligation for a given compliance period. For Phase 1, the EUCR covers the full 2024–2026 period and is submitted after the period closes; the verifier’s role is to confirm the operator has cancelled units from approved programmes, of approved vintages, in the correct quantity per the SGF-derived obligation. If the operator’s total offsetting requirement for Phase 1 is less than 3,000 tonnes CO₂, the operator is exempt from offsetting for that period — a de-minimis carve-out for smaller carriers. EUCR submission deadlines and templates are State-authority-specific within the ICAO Annex 16 Vol IV framework.

VCUs (and other EEUs) issued from 2021 onward require an Article 6 Authorized – International Mitigation Purposes label to be eligible for use towards CORSIA. The Paris Agreement’s Article 6 governs international transfer of mitigation outcomes between countries; the “Authorized” label confirms that the host country (where the project is located) has formally authorised the credit to be used for international purposes — including making the corresponding adjustment to its own NDC accounting. The label is what prevents double-counting between the host country’s national climate target and the airline-jurisdiction offsetting claim. Procurement panels at sophisticated buyers now check for the label before accepting CORSIA-bound credits. For Thai-origin T-VER Premium credits intended for CORSIA use, Article 6 authorisation runs through Thai government channels — adding a regulatory dimension that Othello’s bench navigates as part of the supply-side engagement.

CORSIA Verifier is the compliance-market anchor of Othello’s seven-credential ESG-assurance cluster, alongside AA1000AS ACSAP, ISO 14064 Lead Auditor, TGO CFO + CFP Auditor, Verra Lead Assessor, ICVCM CCP, and ISCC PLUS — all held by Panit Chancharoonpong. The aviation compliance market and the voluntary carbon market intersect: Thai-jurisdiction T-VER Premium projects can be developed for CORSIA use; Verra-issued VCUs are CORSIA-eligible with Article 6 authorisation; airline buyers need verified Emissions Reports under Annex 16 Vol IV and verified offset supply under Verra/T-VER program rules — and Panit’s credentials span all of these. Founded 2020 on US Government bilingual contracts under FAR-grade contractor verification, the firm’s procurement-grade audit-trail standard applies to CORSIA engagements the same way it applies to ATA-certified translation or 56-1 One Report disclosure. One engagement letter, one NDA from first email, one audit-trail Bangkok-side, twenty credentials behind it. Email [email protected] or call +66 02-859-2145.