Goods are flowing effectively between Great Britain and Northern Ireland, the Government said.
The end of the transition period has produced deep-seated structural problems which will not be quick to resolve, the Road Haulage Association (RHA) has said.
The Government must intervene with extra cash before jobs are lost at freight companies, the industry warned.
A UK Government spokesperson said: “Goods are flowing effectively between Great Britain and Northern Ireland and there is no disruption at Northern Ireland ports.
“The grace periods for businesses moving goods between GB and NI are in operation and working well.
“We are aware of specific issues related to moving mixed food loads, known as groupage, and new guidance is coming soon following a successful trial with industry.
“To ensure that traders have the support they need to adapt to the new practicalities, we have set up the £200m trader support service which provides free advice and support to businesses of all sizes.
“We are committed to working with industry and the Northern Ireland Executive to address any issues that arise.”