About 40 lorries a day will be subject to new Irish Sea border checks when they enter Northern Ireland from Great Britain, NI's chief vet has said.
Robert Huey's staff in the Department for Agriculture will be responsible for carrying out these checks.
Dr Huey has been outlining new guidance for traders about what they need to be prepared for when the changes come.
The checks will start on 1 January when the Brexit transition period ends.
At that point Northern Ireland will still be in the EU's single market for goods while the rest of the UK leaves.
That will mean new paperwork, processes and checks for moving food products from GB-NI, although some of these will be phased in.
Dr Huey urged anyone involved in food or animal trade to read the guidance published by his department.
He said: "While some of the new processes will be phased in over time, many of them start immediately - therefore people should read these guides as soon as they can.
"It is clear how complex the food, animal and plant supply chains are and these documents explain how to navigate the changes.
Dr Huey had already indicated that the food industry will not face penalties for non-compliance with new rules during the first week of 2021.
But he has reiterated that after that, the approach to compliance will be tougher.