Trading has started on NZX's debt and equity markets after issues with the derivatives market meant trading was unable to take place in the morning session.

The market open was pushed out to 12.45pm for the main stock board and Fonterra shareholders' market and 12.30pm for the debt market, the stock market operator said this morning.

NZX said it had resolved the problem with the derivatives market, and was working with its suppliers on what caused the issue, which related to a component of the derivatives market functionality.

"NZX is conscious of the impact of these delays on market participants, and we have been working with all parties during the morning to update on progress," it said.

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Last year, an internal mistake shut down the stock market for the better part of a day when an error was made during normal system testing. At the time, chief executive Mark Peterson was at pains to point out that the X-stream trading system wasn't at fault and was very stable.

The stock market operator introduced the Nasdaq system in 2014, which let it branch out into new securities trading such as derivatives and commodities.

NZX is upgrading the trading system as part of its five-year strategy to support secondary market growth and development. The new system is scheduled to go live in April or May next year.

- BusinessDesk