Some 42% of all firms that trade across the Irish border are already reporting a negative 'Brexit' impact on sales.
That is according to the latest InterTradeIreland Business Monitor.
While 38% cite that Britain's exit from the EU has impacted negatively on investment decision-making within their firm.
There have also been additional negative impacts on supply chains and logistics for more than a quarter of exporters to date.
Source: InterTradeIreland
But it also found that 41% of all firms trading across the border are growing - with 30% are experiencing rapid growth in sales, compared to 18% that do not export.
The figures for the third quarter of 2018 show trade has remained resilient over the past quarter, reflected in the number of companies continuing to grow.
Source: InterTradeIreland
Meanwhile a skills shortage is an issue that is being felt more specifically by certain types of businesses and certain sectors.
Over one in five (26%) of businesses are experiencing difficulty recruiting, but this rises to 36% for large businesses and 29% and 31% in the construction and professional services sector respectively.
Some 41% of larger firms say there are skills shortages within their sector.
Rising costs of overheads and increasing energy costs are also a significant factor for firms - with 51% reporting it as an issue.
Source: InterTradeIreland
Aidan Gough is the director of strategy and policy at InterTradeIreland.
"The figures from our latest Business Monitor are supported by InterTradeIreland's latest research which shows that SMEs that export, including cross-border traders have significantly better outcomes across a range of key indicators including turnover, employment and productivity.
"Goods firms exporting across the border have 9% higher levels of productivity than firms that don't export beyond their local market, moreover turnover is almost 100% higher and employment is almost doubled.
"Expanding participation in cross-border trading makes an important contribution to the individual performance of the firm and to the wider economy."
