Vocus said the due diligence was likely to take a number of weeks and it had granted EQT the access to enable it to put forward a formally binding proposal.
"The board notes that there is no certainty that this process or the indicative proposal will result in an offer for Vocus," the statement said.
"Vocus shareholders do not need to take any action in response to the indicative proposal at this time. Vocus will update shareholders, in accordance with the company's continuous disclosure obligations, in due
This came shortly after reports said a bid was being made for Vocus by the American equity firm Kohlberg Kravis Roberts.
Vocus has been hit by the ever-decreasing margins of its broadband business as the NBN Co has made it difficult for RSPs to turn a profit. Its retail business was written down by about $1 billion in 2017.
The company said it had appointed UBS as its financial adviser and Allens as legal adviser.
In October 2016, a plot to oust Vocus chief executive Geoff Horth led to the departure of Spenceley and fellow board member Tony Grist. Vocus shares slumped to a 13-month low after the incident.
Another big fall, by more than a quarter, occurred in November the same year and saw $874 million wiped off its value after it shared its first guidance to expected earnings along with its new acquisitions, NextGen Networks, M2 Group and Amcom.
In May 2017, Vocus issued its second profit warning in six months, leading to another big fall in share prices, this time by 30%. Soon after, there were reports that Vocus was looking at selling off its data centres.