Tea companies here say they are braced for Brexit bureaucracy and supply problems at ports, which one warned could result in rising consumer prices.
hompson's Tea and SD Bell's, family firms founded in the nineteenth century, bring in raw materials from Great Britain and overseas.
Under the terms of the Northern Ireland Protocol, from January 1 they will have to complete customs declarations for goods imported from Great Britain.
Robert Bell, the owner of SD Bell & Co, said: "If these administrative hurdles cause further delay, there will be cost to the consumer because I'll have to buy things in earlier and in greater volume to mitigate any potential delays we incur.
"The customer will end up having to bear some of the cost and I will too."
He said he was also concerned about bottlenecks at ports in England. Gridlock at Felixstowe in Suffolk has already been delaying shipments of tea tins from China, he explained.
Aodhan Connolly, director of the Northern Ireland Retail Consortium, said the firms' predicament demonstrated the integrated nature of supply chains.
"It's not just an integrated supply chain on this island, it's an integrated supply chain on these islands," he added.
"What I can say with some certainty is that prices will be up. To mitigate that, we have to make sure they don't go up too far."
Ross Thompson, director of Thompson's Tea in Belfast, said he had stockpiled "corridors of hundreds of metres of tea" and large volumes of teabag paper. "We have tea chests piled 20-feet high," he added. He said that while imports of tea leaving India and Kenya would be unaffected by Brexit, he had concerns about continuity in supply of packaging materials from England.
"We're building up materials so that in case of disruption, confusion or congestion at ports, we have enough to tide us over in difficult times," he added.
Mr Thompson said that a million of his company's teabags were being consumed every day in lockdown Northern Ireland.
"We were staggered by the amount of continuous purchasing and we're relieved we were able to keep up," he said.
He said the company had absorbed rising costs during Covid rather than pushing up prices.
"We were concerned about lockdown at our growing regions. Lockdown in Assam, our favourite area for growing, affected the crop badly for about six weeks," he said.
"Prices soared to record highs, but we still decided to purchase our normal requirements to have consistency and decided to absorb those within our costs."
He said Thompson's had also doubled normal stock of its fresh tea leaves in preparation for the future, adding: "Brexit could be really smooth, but blockages or serious delays could deny us materials we require from England.
"We've built stocks of teabag paper because we worry about delays, which could bring some cost implications.
"We feel we have coped and will do our best to absorb that, but interruption of supply is huge concern. It's the most unusual set of challenges we've gone through since 1896."
Separately, companies have been warned to prepare now for the end of the transition period.
Speaking at a webinar hosted by business advisory firm Grant Thornton, Lee Squires, the company's head of indirect tax, said that regardless of whether a deal was reached, businesses must be ready for checks on goods.