Shipping companies working on EU ETS compliance regularly encounter several system names: THETIS-MRV, MOHA and the Union Registry.
THETIS-MRV is the key system entry point for completing EU MRV reporting and submitting EU ETS emissions data. It is used mainly for monitoring plans, emission reports and company-level emissions data. Holding and finally surrendering EUAs, by contrast, is done through the Union Registry and a MOHA account.
Put simply: THETIS-MRV answers the question of how emissions data is reported and verified; MOHA and the Union Registry answer the question of where allowances are held and how surrender is completed.
1. What is THETIS-MRV?
THETIS-MRV is the online system operated by EMSA to support implementation of the EU MRV regime. As EMSA explains, the MRV rules require shipping companies to report emissions data and related information for large ships calling at EU/EEA ports, with verifiers confirming the reported data. THETIS-MRV provides system support for companies, verifiers, flag states and other parties involved.
With shipping brought into the EU ETS, the role of THETIS-MRV has expanded further. It serves not only traditional MRV emissions reporting but also connects with company-level emissions reporting and the calculation of allowances to be surrendered under the EU ETS.
2. Step one: configure company and ship information
Before a monitoring plan or emission report can be created, a company first has to complete basic configuration in THETIS-MRV.
This typically covers the company account, user permissions, adding ships to the fleet, periods of responsibility and the link to the verifier. Only once it is clear which company is responsible for which ship and during which period can work continue on monitoring plans, emission reports and company-level aggregation.
EMSA likewise treats system configuration as preparatory work that comes before drafting monitoring plans and generating emission reports in THETIS-MRV.
For a shipping company this step is more than "opening an account". If ship management responsibility, the ISM company, ship ownership relationships or management periods are unclear, subsequent reporting and company-level aggregation may all be affected.
3. Step two: submit and maintain the monitoring plan
The monitoring plan is the basis for all later emissions reporting.
A company must prepare a monitoring plan for each ship under its responsibility, setting out how fuel consumption, voyages and time at berth will be monitored, which emission calculation methods are used and where the underlying data comes from. The monitoring plan must be submitted to an independent accredited verifier for assessment and, following that assessment, submitted to the responsible administering authority. EMSA states that shipping companies should submit the monitoring plan for each ship to an accredited verifier for assessment and then to the responsible administering authority.
It is worth noting that a monitoring plan is not "submit once and leave unchanged". If fuel types, emission sources, monitoring methods, data flows or management responsibility change, the company should assess promptly whether the monitoring plan needs to be updated.
This matters in particular because, from 2026, the maritime element of the EU ETS also covers CH₄ and N₂O. Ships using fuels such as LNG need to pay close attention to whether the monitoring plan still matches actual fuels and emissions.
4. Step three: record or upload voyage, port and emissions data
Throughout the reporting year, companies need to record and manage data on voyages, time at berth, fuel consumption and emissions on a continuous basis.
THETIS-MRV allows companies to record voyage and port emissions, and this data then forms the basis for creating MRV/ETS emission reports and FuelEU reports.
In practice, this step determines the data quality of the annual report. Whether voyage boundaries are clear, whether emissions at berth are complete, whether fuel data is traceable and whether periods of responsibility are accurate all affect the ship-level emission report and the company-level aggregation that follow.
Companies should therefore not leave data entry and clean-up until shortly before the reporting deadline, but maintain the relevant records as part of day-to-day operations.
5. Step four: create and submit the annual ship-level emission report
After the end of the reporting year, the company creates the annual emission report for each ship on the basis of monitoring data and submits it for verification.
Since 2025, companies must submit the annual emission report for the previous reporting period for each ship under their responsibility by 31 March each year. The administering authority may require earlier submission, but not before 28 February.
This report answers one main question: how much did this ship emit during the previous reporting period.
Where a ship is sold, changes manager or changes company during the reporting period, a partial emission report may also be required. EMSA's tutorials explain specifically how, within the MRV/ETS legal framework, a partial emission report is created and submitted when a ship moves from company A to company B within the same reporting year.
When creating reports in the system, companies should therefore pay particular attention to periods of responsibility and data boundaries, so that a change of company or handover of a ship does not blur the scope of the report.
6. Step five: produce the company-level emission report
Under EU ETS compliance, once ship-level reports are complete, a company-level emission report or company-level aggregated emissions data must also be produced.
EMSA notes that, from 2025, by 31 March each year shipping companies must also submit a company-level emission report for ships within the scope of the ETS Directive, aggregating the data used for ETS purposes at company level and having it verified to the verifier's satisfaction.
One way to look at it is this:
The annual ship-level emission report answers "how much did this ship emit"; the company-level emission report answers "how much EU ETS compliance emission does this company have to account for".
Company-level emissions data is an essential basis for calculating EUA requirements and completing surrender by 30 September. If ship-level data is incomplete, periods of responsibility are unclear, or there are issues with the scope of company-level aggregation, both allowance calculations and procurement arrangements will be affected.
7. One point to note: THETIS-MRV is not the surrender system for EUAs
THETIS-MRV covers monitoring, reporting, verification and submission of company-level emissions data. Surrendering EUAs, however, does not take place in THETIS-MRV.
After verified emissions data has been produced and submitted in THETIS-MRV, the company still has to calculate the quantity of EUAs to be surrendered on the basis of in-scope EU ETS emissions and the applicable compliance ratio for the year, and then hold and surrender the allowances through the Union Registry and MOHA.
Across the full compliance chain, THETIS-MRV handles the data side, while MOHA and the Union Registry handle the allowance account and surrender side. The two must connect, but their functions are distinct.
Conclusion
EU ETS compliance in shipping is not a single action within one system. It is a complete loop, running from data submission in THETIS-MRV through to allowance surrender in MOHA and the Union Registry.
If you have requirements relating to annual EU ETS compliance planning, EUA procurement or allowance demand calculations, you are welcome to contact Tecway Maritime.
References
- European Maritime Safety Agency, THETIS-MRV
- European Maritime Safety Agency, THETIS-MRV Tutorials – Companies
- European Maritime Safety Agency, FAQ MRV Regulation
- European Maritime Safety Agency, MRV Regulation