NZX is taking legal action over its purchase of the Australian Clear Grain Exchange business two years ago.
The stock market operator alleges breach of warranty and other claims from the $6.4 million deal.
The suit is against Ralec Commodities, Ralec Interactive, Grant Thomas, Dominic Pym and other related parties.
The size of the claim has not yet been determined.
When it purchased the business in 2009 as part of its push into agricultural commodities trading, NZX said the Melbourne-based exchange would provide some of the technology and expertise needed to help build a dairy futures plans here.