Yes, there must always be a pre-notification.
The document type depends on the route and the customs procedure chosen:
- Will your goods be shipped directly from the Netherlands to Ireland?
Then you are transporting Union goods to another Union country. Then use document type ICT (union transaction).
- Will your goods be unloaded in the UK and then go to Ireland by truck?
Your goods then go to a non-EU country. Consult with your customs agent about the customs regime under which you will have the goods transported.
It is customary to have the goods transported under customs transit from the Netherlands to Ireland. In this case you use document type TT1 (Regulation external through Union transit).
For further explanation, please refer to the manual for use of document types for export.