Q14: Extra data seems required. Isn’t it too complex?

The fuel data is available from the already obligatory fuel receipts (so called Bunker Delivery Notes).
That's enough.
In the new refund version, no extra data is required.

Previous alternative based on final destination of goods

The following description is shown for historical reasons. It also demonstrates the simplicity and advantages of the currently preferred, refund version.
In the previous version, the levy was only to be paid at lower than 100% level once the ship demonstrated that it was entitled to the reduced rate through the selected responsibility measure (such as the ship’s ratio of delivered cargo to Annex I countries). We understand that this single number can be extracted from the cargo data available for the ship charterers without much effort.

This additional measure will not even be required for many ships. The majority of oil tankers and cargo ships would pay either 100% or 0% in a given period, as they are typically bound for a single destination, either to an Annex I or non Annex I country/countries (for instance a tanker chartered to transport crude oil from the Gulf to the USA).

For container ships, the responsibility measure could be the share of full containers destined to Annex I countries (expressed in TEUs). This information is available from the systems operated by the liners, as the destination of container is practically always known. For the very limited number of “ghost containers”, this loophole is expected to be fixed in the near future, mainly for supply chain security reasons. Implementation for liners would be made easier thanks to the high use of ICT systems and very high concentration in the sector (16 companies comprise 80% of the sector).