UPDATE 2-Australia's Nuix share price collapses after second revenue warning

* Downgrades revenue and contract value for 2nd time

* Shares fall over 19%, trading at less than half IPO price

* Uncertainty is regarding precise timing of contracts - CEO (Recasts, updates with share price, CEO comment)

SYDNEY, May 31 (Reuters) - Australian software provider Nuix Ltd’s value plunged over 19% on Monday after the company downgraded its fiscal 2021 revenue forecast for a second time, citing uncertainties related to expected sales to existing and new customers.

The downgrade is the latest blow to Macquarie Group-backed Nuix, which has faced criticism over its accounting policies and whose shares have lost over half their value since its listing in December.

The company cut its expected FY21 pro-forma revenue range to A$173 million to A$182 million ($133.4 million-$140.3 million), from the A$180 million to A$185 million downgraded forecast it provided in April.

It also downgraded its outlook range for annualised contract value - a key metric - to A$165 million to A$172 million, from the A$168 million to A$177 million it said it expected a month ago. The latest range is 14% to 17% lower than the company’s guidance in its Dec. 4 prospectus.

Nuix’s capital raising and listing, managed by its part-owner Macquarie Group and Morgan Stanley, was the nation’s second-largest in 2020. With a 30% stake, Macquarie remains Nuix’ largest shareholder.

Its shares skyrocketed soon after the listing but are now trading at less than half its A$5.31 IPO price.

“We understand the importance of meeting financial forecasts,” Nuix CEO Rod Vawdrey said in a statement.

“There’s a near-term level of uncertainty regarding the precise timing, shape and scope of some large and anticipated customer contracts coming to fruition in the next few weeks.”

The company expected to capture most of the revenue currently under negotiation with those customers either by financial year-end or early in the new financial year, he added.

“We remain confident in the long-term outlook for the company,” he said.

Nuix’s governance and the quality of its financial accounts have been criticised by the media and proxy advisory firms that have questioned its revenue recognition policies for multi-year contracts.

The company has terminated a consultancy agreement with co-founder Tony Castagna, who is the subject of a police investigation over possible breaches of the Corporations Act.

The company left its earnings guidance unchanged. ($1 = 1.2970 Australian dollars) (Reporting by Paulina Duran in Sydney and Soumyajit Saha in Bengaluru; Editing by Stephen Coates)