- Opening Single Price Auction and Single Open: The existing five-group opening sequence will be replaced with an Opening Single Price Auction (OSPA) followed by a unified Open in a randomised auction time window. This will mean all equities and ETFs open at the same time, within a 30-second to 60-second range between 9:59:45am and 10:00:00am AET.
- Post Close Trading Session: Introduces a new lit-order trading period following the Closing Single Price Auction (CSPA), allowing execution at the established closing price. The Post Close trading session will commence at 4:11:00pm and end at 4:21:50pm AET.
- Closing Single Price Auction Enhancements: Enables securities with late-breaking announcements to participate in closing auctions while maintaining Post Close session eligibility.
The ASX trading platform is schedule for a comprehensive upgrade which is expected to go-live on Monday the 23rd of June. There are a number of key changes, particularly to the market open and close phases.
Opening Single Price Auction (OSPA) and Single Open:
The opening single price auction window initiates at 9:59:00am with a 15-second randomisation period, ensuring fair order matching across all equity instruments. Continuous trading commences between 9:59:45am and 10:00:00am, compressing the previous 15-minute staggered open into a maximum 60-second auction window following which all equities and ETFs open for trading simultaneously.
- Permitted Actions: Order cancellations are allowed during OSPA
- Prohibited Actions: New order entry and order amendments are not allowed during OSPA, to maintain auction integrity
- Price Determination: The ASX’s existing imbalance-driven pricing algorithm remains unchanged, prioritising maximum executable volume at equilibrium prices.
- What this means for you: During this phase, Market to Limit orders will be rejected. Any new limit orders and amendments will queue until the market (or security) moves to Open status.
Opening Single Price Auction for Cash Markets
Post Close Trading Session State (Post_Close):
The Post Close session introduces a new lit-order trading session following the CSPA, operating from 4:11pm to 4:21:30pm. This session allows participants to enter new orders and amend existing orders, provided they are at the CSPA price.
- Post Close Price: All orders must match the Closing Single Price Auction to be considered for execution. Limit orders entered outside closing price will be entered at Preopen (7am) the following trading day.
- Order Types permitted: Limit orders will be allowed at the CSPA price, provided a CSPA price exists. Limit orders away from the CSPA price will be entered at 7am on the following trading day. Market to limit orders are allowed and can trade at the CSPA price, provided a CSPA price exists. If the security did not participate in CSPA, and no closing price exists then Market to limit orders will fail and Limit orders will be entered at 7am the following trading day.
- Priority Carryover: Orders unfilled during CSPA retain queue priority, incentivising participation in the primary auction.
- What this means for you: During this phase, Market to Limit orders will be rejected. Any new limit orders and amendments, which are away from the CSPA (or where there is no CSPA), will queue until the following morning.
Session States and Post Close Summary
