Business groups are warning the UK and EU to urgently reach a deal on Brexit.
Only 37% of British Chamber of Commerce members that trade with Ireland, are preparing for possible changes at the border - compared to 59% of firms in the North.
Northern Ireland Chamber, Chambers Ireland and the British Chambers of Commerce are jointly calling on politicians to move quickly to reach an agreement.
Chambers Ireland Chief Executive Ian Talbot says firms need to know what is going to happen so they have time to adjust.
"It's absolutely imperative that we get some degree of certainty within the next two months about what's going to happen next March," said Mr Talbot.
"The ideal for us would be that the right building blocks are put in place to ensure we have the transition period that gets us out to December 2020.
"Even that may not be enough but at least it buys some time for companies to plan properly."
Meanwhile, Tánaiste Simon Coveney is hosting the government's first Brexit ready roadshow at Páirc Uí Chaoimh in Cork this morning.
The exhibition will bring together the major state agencies under one roof to give businesses advice on Brexit.
It is open between 9am and lunchtime.
Simon Coveney says he will give an update on negotiations at the start of the event, which is the first of a number to take place around the country this month.
"We're starting in Cork in Páirc Uí Chaoimh, then we're moving to Galway, then we're moving to Monaghan, then we're moving to Dublin so it's a big roadshow involving a lot of the agencies in the State
"It is really worth your while if you're a small business - figuring out how you're going to prepare for Brexit - to come along and listen to the experts."