Bonjour Thibaut,
How nice that you are planning a trip to our island! 😊
The passport number seems to be a required field in the Passenger Locator Form, since it will be mentioned in the receipt you will receive after completing it. You can find more information on how to fill it in
here.
I would encourage you to contact the authorities per mail (
passengerlocatorform@plf.ie) or to get in touch with your airline or ferry company for more details.
I would be glad to help you if you need some advice about visiting the island. ☘
J'espère que ces informations vous seront utiles.
Bonne journée,
Sophie