Australian dealmakers are battling to rescue A$38 billion ($24 billion) worth of mergers that have been terminated or challenged by regulators and shareholders.

The value of these deals is equivalent to about 40% of the year’s A$96 billion in announced transactions targeting Australian companies, according to data compiled by Bloomberg.

Many of the takeover proposals were abandoned or challenged in the second half of this year as concerns have mounted over higher borrowing costs and an uncertain economic outlook. That includes three of the nation’s top five deals this year, most prominently the A$19.4 billion takeover of Origin Energy Ltd. by a Brookfield Asset Management-led group.

While data on withdrawn or terminated deals are yet to register the decline as many deals are still being fought out, the pattern marks a clear change from the boom in mergers two years ago. M&A volume has slowed to about A$144 billion this year, less than half of an all-time high of A$379 billion in 2021, data compiled by Bloomberg shows.

Megadeals face a unique set of problems as they need longer completion time, exposing them to more scrutiny as well as changing markets, according to Phil Breden, a Sydney-based partner at law firm Ashurst LLP.

“Deals continue to be done, but deals take longer,” he said. “Where you have a long period between signing and closing, keeping that deal on track can be challenging, whether from general market conditions or changes specific to the target or the bidder.”