Northern Ireland business, freight and farm organisations have highlighted a litany of problems within the first week of the operation of the Northern Ireland Protocol, pointing to a lack of information for traders and poor preparedness, especially among companies in Britain exporting goods to Northern Ireland.
The House of Commons Northern Ireland Affairs Committee heard evidence of food consignments being prevented from crossing to Northern Ireland because of a poor understanding of the paperwork required.
There have also been instances of GB suppliers preferring not to ship food products to Northern Ireland retailers.
On one occasion, a haulage firm was forced to resort to YouTube to work out what paperwork was required when bringing food consignments into Northern Ireland, the committee heard.
Overall, the testimony of the Northern Ireland Retail Consortium, Freight NI and the Ulster Farmers' Union painted a picture of a lack of preparedness and official information, compounded by confusion over what the grace periods, agreed by the EU and UK in December, actually entailed.
The effects have so far been cushioned by a light touch approach by Northern Ireland and EU officials operating at northern ports, and the low volumes of trade due to the traditionally slow start to the year, the impact of the Covid pandemic, and the fact that many importers had stockpiled goods in December, witnesses said.
The committee was hearing evidence from Aodhán Connolly, CEO of the Northern Ireland Retail Consortium, Seamus Leheny, policy manager for Freight NI, and Victor Chesnutt, president of the Ulster Farmers' Union.
The committee heard of grave concerns that when trade flows reach their normal levels in the third week of January then there could be significant problems.
Gregory Campbell, DUP MP for East Londonderry, told the committee: "We need to understand the scale of the likely problem six to eight months from now."
DUP MP Ian Paisley described the Protocol as an "unmitigated disaster" and said it should be "removed" by invoking Article 16, as the Protocol was proving to be an impediment to UK trade.
Article 16 states that if application of the Protocol leads to persistent "serious economic, societal or environmental difficulties" then either side could unilaterally take "appropriate safeguard measures".
Chair of the Committee Simon Hoare MP said the idea of invoking Article 16 just days into the operation of the Protocol would be "slightly eccentric".
Aodhán Connolly told the committee that official government guidance on moving parcels had only been issued the day before the Protocol took effect on January 1.
Issues such as VAT rules and Rules of Origin were "very confusing" for traders, especially for car dealers, he told the committee.
There were unforeseen legal consequences, such as who paid for costs caused by delays, if such costs were not written into the contract.
Mr Leheny told the committee everything was "last minute" and there had been significant upheaval.
One company had informed him that one customs declaration, for a consignment entering from GB, had taken 12 hours to process.
He said a customs clearance centre was supposed to be manned by 70 staff, but over the opening weekend only four staff had been on duty.
Mr Leheny highlighted the problem of "groupage", whereby a lorry travelling to the UK would traditionally make multiple pick ups.
Because each consignment needed a customs declaration this was not causing significant concerns, as was the fact that lorries containing food products could no longer engage in groupage because the container had to be sealed with the first collection.
He told the committee that many companies in Great Britain were simply not aware of the new obligations required by the Protocol to complete customs declaration and to pre-notify the movement of food products to the EU's TRACES system, which monitors the movement of food products and live animals into the EU.
As a result, a large manufacturer had to prevent 15 food lorries from travelling to Northern Ireland because it had not completed customs formalities.
The committee heard that operators had misunderstood that the grace periods of three and six months for certain food products only meant the waiving of Export Health Certificates (EHCs) for products of animal origin, and did not mean that companies were exempt from customs declarations, or TRACES pre-notifications.
Mr Chesnutt said that Northern Ireland livestock farmers were heavily dependent on grain for animal feed, and supplies had previously come thanks to the EU-Ukraine free trade agreement.
However, because of Brexit, there was a quota implication for such grain and maize imports and as a result Northern Ireland livestock companies would be hit by up to £2m (€2.2m) in tariffs.
This is because such imports into Northern Ireland were at risk of crossing the border into the Republic. A potential rebate system for livestock owners to recoup the tariffs had not yet been set up.
Mr Connolly told the committee that the EU and UK should continue discussions via the so-called Joint Committee, set up under the Withdrawal Agreement, in order to extend grace periods and to create a long term workable solution.