On Jan. 8, IEX issued circular on market wide circuit breaker testing.
IEX issued notice on Information Circular 2025-0003 on the mandatory participation in market wide circuit breaker (MWCB) testing for certain designated members.
MWCB Testing
Pursuant to IEX Rule 11.280(i), members who meet designation criteria for mandatory participation in testing of backup systems per IEX Rule 2.250, designated members.
Now required to participate in at least one scheduled MWCB test each year.
Members must verify participation in test by attesting that they are able to receive and process MWCB halt messages from the securities information processors (SIPs).
Also, must verify they can receive and process resume messages from the SIPs following a MWCB halt, and market data from the SIPs relevant to MWCB halts.
And, send orders after Level 1/2 MWCB halt in a manner consistent with usual trading.
Testing year consists of 4 quarters immediately following quarter in which IEX determined that a member contributed a meaningful percentage of IEX overall volume.
2025 Testing Year for member that is determined Q1 2025, Apr. 1 to Mar. 31, 2026.
After test concludes, participating members are required to complete attestation.
Testing Schedule
2025 testing schedule is Saturday, Apr. 5, 2025 for failover, MWCB Level 1/2 Test #1.
Jul. 26, 2025, for failover, MWCB Level 1/2 Test#2; Sep. 13, 2025, for dedicated MWCB Level 1, 2, and 3; and Dec. 6, 2025, for failover, MWCB Level 1 and 2 Test #3.
