Service Release 15 (SR15) in ASX Trading Platform: Complete Guide
Service Release 15 (SR15) represents a transformative update to the ASX trading platform, scheduled for implementation in May 2025. This release introduces five critical enhancements aimed at streamlining market operations, improving price transparency, and modernizing trading protocols. Key changes include the elimination of the Opening Auction stagger, the introduction of a Post Close trading session, refinements to Company Sensitive Price Announcement (CSPA) handling, simplification of trade reporting codes, and the phased replacement of legacy protocols with modern FIX-based systems. These modifications are designed to align ASX market dynamics insights with global best practices while addressing long-standing participant concerns about auction efficiency and post-trade liquidity.
What is Service Release 15 (SR15)?
Service Release 15 (SR15) is a comprehensive upgrade to the ASX trading infrastructure, marking the exchange's most significant operational overhaul since the introduction of ASX Trade in 2016. The release targets inefficiencies in auction mechanisms, enhances post-close liquidity opportunities, and modernizes data dissemination protocols. SR15's development followed extensive consultation with market participants, regulators, and technology vendors, reflecting a collaborative approach to addressing systemic challenges.
Key Components of SR15
The release consolidates five strategic initiatives:
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Removal of the Opening Auction Stagger: Replaces the fragmented five-group opening sequence with a unified randomized auction window, reducing market fragmentation during pre-open phases.
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Post Close Trading Session: Introduces a 10-minute, lit-order trading period following the Closing Single Price Auction (CSPA), allowing execution at the established closing price.
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CSPA Enhancements: Enables securities with late-breaking announcements to participate in closing auctions while maintaining Post Close session eligibility.
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Trade Code Simplification: Rationalizes 12 legacy block and late trade codes into two standardized categories, reducing compliance complexity.
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Protocol Modernization: Initiates the sunsetting of OMNet infrastructure with FIX 5.0 SP2 adoption and a new multicast Market Data Feed (MDF).
Implementation Timeline
ASX has structured the SR15 rollout across four critical milestones:
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IWT 1 (April 12, 2025): Initial industry-wide testing of core auction changes.
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IWT 2 (May 3, 2025): Final dress rehearsal during ASX's Business Continuity Planning weekend.
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Go-Live Readiness (May 10, 2025): Production environment finalization.
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Go-Live (May 12, 2025): Full production deployment, excluding FIX Order Entry and MDF, which follow in Q3 2025.
How Will the Opening Auction Stagger Changes Work?
The existing five-tiered opening auction structure, which staggered different instrument classes across 15-second intervals, has been replaced by a unified Open Single Price Auction (OSPA) mechanism. This change addresses longstanding concerns about market fragmentation and information leakage during pre-market phases.
New Opening Auction Structure
The OSPA window initiates at 9:59:00 AM with a 15-second randomization period, ensuring fair order matching across all equity instruments. Continuous trading commences between 9:59:45 AM and 10:00:00 AM, compressing the previous 15-minute staggered open into a maximum 60-second auction window. Notably, index derivatives (options and warrants) retain their 9:49:45 AM open to align with SPI Futures, while Single Stock Options (ETOs) begin at 10:00:05 AM to accommodate volatility hedging.
Operational Constraints During OSPA
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Permitted Actions: Order cancellations, trade reporting, and cancel-on-disconnect functionality remain active.
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Prohibited Actions: New order entry and order amendments are suspended to maintain auction integrity.
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Price Determination: The ASX's existing imbalance-driven pricing algorithm remains unchanged, prioritizing maximum executable volume at equilibrium prices.
What is the New Post Close Trading Session?
The Post Close session introduces a 10-minute, lit-order continuum following the CSPA, operating from 4:10:30 PM to 4:21:00 PM. This session allows participants to trade residual interests at the established closing price, effectively extending price discovery while maintaining market stability.
Trading Mechanics and Constraints
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Price Fixing: All orders must match the CSPA-derived closing price; deviant orders face immediate rejection.
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Order Types: Limit, Sweep Limit, Market-to-Limit (MTL), and Sweep MTL orders are permitted, with Block Trades (deal source 90/91) allowed but Late Trades prohibited.
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Priority Carryover: Orders unfilled during CSPA retain queue priority, incentivizing participation in the primary auction.
The session automatically cancels if no valid closing price exists, preventing erroneous trading in illiquid securities.
How Will CSPA Enhancements Handle Sensitive Announcements?
SR15 introduces nuanced handling for securities issuing market-sensitive announcements during the CSPA's Pre-No Reference (PRE_NR) phase. Previously excluded from closing auctions, these securities now enter a dedicated mini-auction at the conclusion of their PRE_NR period, followed by immediate transition to Post Close trading.
Key Process Improvements
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Extended PRE_NR Window: The PRE_NR pause extends from 11:00 minutes to 11:30 minutes, accommodating late disclosures.
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Price Continuity: Securities benefit from Post Close liquidity even after delayed announcements, reducing forced unwinding by market makers.
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Systematic Handling: ASX's trading engine automatically manages state transitions, eliminating manual intervention requirements.
What Changes Are Coming to Block and Late Trade Codes?
SR15 rationalizes Australia's complex trade reporting regime, replacing 12 legacy codes with four standardized identifiers. This simplification reduces compliance overhead while maintaining regulatory visibility.
Code Restructuring
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Block Trades: Legacy S1/S2/S3 codes consolidate into SC (Special Crossing), with automated ASIC tier checks.
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Late Trades: L1-L5 codes collapse into LT (Late Trade) and L5 (Late Put Through), aligning with ASIC's surveillance priorities.
Market participants must update matching engines to parse new deal sources 90-91 for Post Close transactions.
What Protocol Updates Are Included in SR15?
ASX initiates its OMNet decommissioning roadmap with SR15, introducing FIX 5.0 SP2 for order entry/drop copy and a new ITCH-like Market Data Feed (MDF). These changes cater to low-latency participants while maintaining backward compatibility.
Migration Timeline
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FIX Drop Copy: Available in CDE+ from December 18, 2024, with production deployment coinciding with SR15 go-live.
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FIX Order Entry/MDF: Testing commences June 2025, targeting Q3 2025 production release.
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OMNet Retirement: Scheduled for SR16 (2026), completing the protocol modernization.
What Other Changes Are Included in SR15?
Trading Halt State Reconfiguration
The Trading Halt session state now persists through end-of-day ADJUST phases, restricting order actions to cancellations and passive amendments. This prevents erroneous order entry during volatile market closes.
CSPA Cancellation Flexibility
Post-uncross order cancellations are now permitted during CSPA, providing participants greater control over residual exposures. These improvements align with data-driven investment strategies that increasingly rely on precise auction mechanics.
Testing and Preparation for SR15
ASX has staggered testing timelines across CDE+ environments:
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Auction Changes: Available since April 17, 2024.
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Post Close/CSPA: Live since June 26, 2024.
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Trade Codes: Released August 21, 2024.
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FIX Drop Copy: Accessible from December 18, 2024.
Participants must validate system readiness against ASX's 78-page technical specification documents and complete mandatory IWT attestations.
Frequently Asked Questions About SR15 Implementation
Are IWT Sessions Mandatory?
Market participants are required to participate in at least one Industry-Wide Testing (IWT) event prior to the SR15 go-live date. This requirement ensures all systems can properly handle the new trading mechanisms, particularly the unified opening auction and Post Close session. While the FIX Drop Copy functionality remains optional for the initial go-live, ASX strongly recommends participation in all three scheduled IWT weekends to identify potential issues early in the testing cycle.
Is the Go-Live Date Confirmed?
While May 12, 2025 remains the target implementation date for SR15, ASX has emphasized that the actual go-live depends on market readiness as demonstrated through IWT results. The exchange has committed to a stable, risk-measured release approach, prioritizing system integrity over rigid timelines. Broad participation in testing events is crucial to ensure all market segments are prepared for the transition.
Where Can I Find More Information?
Comprehensive documentation is available through the ASX Equity Market Working Group webpage, including technical specifications, test scenarios, and implementation guides. Market participants can also engage directly with ASX through bilateral discussions, their Technical Account Manager, or Customer Technical Support via email at cts@asx.com.au or equities@asx.com.au.
Conclusion
SR15 represents ASX's most ambitious market structure reform in a decade, addressing critical gaps in auction efficiency, post-trade liquidity, and protocol modernity. By aligning with global standards like FIX and adopting randomized auction timing, ASX enhances its competitiveness while reducing participant operational burdens. Successful implementation hinges on industry-wide collaboration during testing phases, particularly in validating the new Post Close and CSPA workflows. Market participants should prioritize system updates and staff training to capitalize on SR15's liquidity opportunities and avoid transitional risks. These changes ultimately support long-term market strategies and enhance the exchange's position within global digital transformation trends. For more comprehensive investment insights on how these changes might affect trading strategies, market participants should consult with their brokers and technical advisors.
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