Revenue is to start providing key Brexit advice for transport companies and their drivers who are transporting goods to, from or through the UK after Brexit.
Revenue said the information will be vital in helping truck drivers avoid congestion and delays for trucks coming into, and moving out of, Irish ports.
From tomorrow, Customs officers will be talking with and providing information to truck drivers in Dublin and Rosslare Ports to ensure they understand and are aware of the changes that Brexit will mean for their journeys.
Customs officers will talk with truck drivers as they wait to get the ferry, and will also be available onboard a number of sailings.
Lynda Slattery, Head of Revenue's Brexit Policy Unit, said it is crucially important that truck drivers are aware of, and understand, what they will need to do and what paperwork they will have to provide at check-in, before boarding the ferry.
She said this will ensure that trucks can move through Irish ports with minimum disruption and delay.
"If a truck driver does not have the right documentation, then he or she will not be allowed to board the ferry and will be delayed, perhaps for a considerable time," the Revenue official cautioned.
Ms Slattery said it is especially important for drivers arriving on ferries into Ireland to know where they need to go if the goods they are transporting need to be checked by Customs.
Revenue has produced a leaflet that sets out how the process will work, she said.