All non-EU flagged vessels will need a declaration of entrance, either oral or written, when coming from abroad into the EU.
Now the moment a non-EU vessel enters EU waters, the clock starts ticking and it may only remain in the EU for a period of 18 months, after which the vessel must leave the EU and obtain a stamp from a non-EU country port as proof of its departure from the EU.
Export and re-import formalities will be required for non-EU registered yachts applying for the Return Goods Relief regime.
For Superyachts refits, Inward Processing Relief (IPR) have been able to suspend payment of customs duties when goods, components or raw materials are imported for processing and subsequently re-exported outside the EU.
The TPA allows non-EU flagged, non-EU owned vessels to benefit from VAT exemption on refit works they carry out within an agreed window

