Tuesday, April 23, 2019

Equity Trader Alert #2019 - 34
Reminder: Nasdaq, BX and PSX Market-Wide Circuit Breaker Testing Opportunity on Saturday, June 8, 2019


  • Industry Announcement

Markets Impacted:

Contact Information:


In coordination with other market participants, on Saturday, June 8, 2019, The Nasdaq Stock Market, Nasdaq BX and Nasdaq PSX will be conducting a full-day test of all three Market-Wide Circuit Breaker (MWCB) breach levels (7%, 13% and 20%) with a simulated next day 9:30am opening. Firms are encouraged to test their ability to receive all messages associated with MWCB, including decline status, halt and resume messages. Firms will also be able to participate in re-opening auctions following the MWCB halts.

June 8, 2019 MWCB Test Script

Part 1: Day 1 Test Timeline
7:00am Nasdaq, BX and PSX pre-market sessions begin
9:30am Nasdaq Opening Cross
9:35am MWCB Level 1 breach, followed by 15 minutes mandatory pause
9:50am Re-opening from MWCB Level 1 breach
10:15am MWCB Level 2 breach, followed by 15 minutes mandatory pause
10:30am Re-opening from MWCB Level 2 breach
10:55am MWCB Level 3 breach and shutdown for “day”
11:25am Conclusion of Day 1 (Part 1 of test)

There will be a break between 11:30am – 2:30pm for markets to shut down and reset their systems to simulate the next day opening.

Part 2: Day 2 Test Timeline

Nasdaq pre-market session begins (simulated 4:00am)

Note: Prior to 2:30pm, Nasdaq will send to the UTP SIP the trading action “H” (Halt) and Reason Code “MWC0” in all Nasdaq-listed names. This will be immediately followed by trading action message with the action code of “Q” (Quote Only) followed by a “T” (Trade Resumption). The “MWC0” code indicates that the stocks are still halted, but clarifies that it is not due to another Level 3 event that day and instead is a carryover from the previous day.

2:35pm BX pre-market session begins (simulated 7:00am)
2:40pm PSX pre-market session begins (simulated 8:00am)
3:00pm Nasdaq Opening Cross (simulated 9:30am)
3:30pm End of test

Note: System timestamps and timestamps represented on messages will not be altered during simulations and will reflect the actual date/time of the test.

2019 Failover/Market-Wide Circuit Breaker Test Schedule

As a reminder, the SIPs have established the following additional Failover/MWCB Saturday test opportunities:

  • August 17, 2019 (SIP Failover; MWCB Level 1 & 2)
  • December 7, 2019 (SIP Failover; MWCB Level 1 & 2)

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