Chartered accountants on both sides of the border are concerned about the future of a smooth post-Brexit customs regime between the EU and UK.
Some 87% of respondents to a survey carried out by the Chartered Accountants of Ireland said that the Republic of Ireland's trade relationship with the UK would be badly affected.
Even if the outcome of Brexit talks between the UK and the EU results in free trade, there will still be customs controls applied.
Customs duties will typically add anything between 2-50% to the cost of imports and exports between Ireland and the UK.
Brian Keegan, director of Public Policy for Chartered Accountants Ireland, said that sensible and practical solutions can be found to minimise disruption to business.
"The arrangements will be between the UK and the EU rather than specifically between the UK and Ireland," he said.
"The best we can hope for is a series of arrangements between the UK and the EU which will defer the disruption of these customs arrangements, or mitigate them as much as possible.
"It may be possible, for instance, to extend the two-year Brexit negotiation deadline from the point of view of Customs, to have transition arrangements which might go a further five years."