BT, Edinburgh International Conference Centre and Apex Hotels are among firms supporting the City Region deal.
The six councils behind the bid claim it will lead to more jobs and improve infrastructure across the Lothians, Fife and the Borders.
It will now be submitted to the UK and Scottish governments.
Edinburgh Chamber of Commerce, Marketing Edinburgh and universities and colleges in the region have also leant their support to the deal.
It is being led by East Lothian, the City of Edinburgh, Fife, Midlothian, Scottish Borders and West Lothian councils.
If the bid is successful, they hope to build new housing, generate jobs and improve connectivity through transport links and the internet.
They believe it could also generate an additional £3.2bn worth of private sector investment.
Andrew Burns, the leader of the City of Edinburgh Council, said: "I am delighted that we have now reached this key milestone and look forward to discussing our proposals in more detail with both governments in the coming months.
"In negotiating this deal, we want to build on our key sector strengths of knowledge, culture and technology."
He added: "Our ambition is to achieve a step change in economic performance for the economies of the region, Scotland and the UK and we are delighted that to date almost 100 businesses have registered their support.
"In addition to this the academic community in the region are also on board. The joint working of public, private and the third sector is crucial to the success of this deal."
A bid to secure £1bn of funding for Edinburgh and the south east of Scotland has won the backing of almost 100 businesses.