Once enacted, there follows a negotiation period on the terms of the UK s relationship that can last up to two years.
One in five are considering moving some of their operations outside of the UK and just one per cent will bring operations back.
The founder and chief technology officer of British tech success Alfresco Software John Newton illustrated the uncertainty UK firms now face.
These include investigating the opening of offices in Ireland and to think finance.
It warned on investment, particularly in tech and R, and in regional funding that will now disappear without the EU.
"Many businesses in the science and technology sectors receive EU research funding, while in poorer regions Local Enterprise Partnerships feed EU money to small business through loans and grants.