Crombie said forming one body would allow greater capacity to deliver more to members, the businesses they served and the Kiwi and Australian economies.
Tim Gullifer, ICAA president, said the timing was right for a new institute.
"In a global environment we need to stay ahead and the One New Institute would give us the scale and strength we need; a larger more sustainable body with increased policy formulation and advocacy capability as well as greater global influence."
Last December, NZICA brought former Fonterra chief executive Craig Norgate on board to oversee the potential merger.
Norgate said at the time he would head the 33,000 member organisation for around 12 months to "sort the future of the institute out".
The vote will be held from October 1 through to November 1 and if members vote in support of the proposed merger, implementation is expected to begin next year.