Nasdaq Texas amends Rule 4121 to lock Level 3 halt resumption at 4 a.m. ET

Nasdaq Texas, LLC filed a proposed rule change on September 25, 2026 (File No. SR-NasdaqTX-2026-048) to amend Equity 4, Rule 4121, which governs the resumption of trading after a Level 3 market-wide circuit-breaker halt. The amendment replaces the existing language that trading would halt "for the remainder of the trading day" with explicit language that trading will not resume until 4:00 a.m. ET or later on the following trading day.

The change is intended to preserve the current 4:00 a.m. ET resumption time when the industry expands to 23-hour, five-day trading sessions (23/5 Trading) slated for December 6, 2026. Without the amendment, the rule's wording could require an earlier reopening at 9:00 p.m. ET on the same calendar day, which Nasdaq Texas says is neither expected nor desired. The Exchange coordinated the proposal with other U.S. equity exchanges and FINRA to maintain a uniform resumption time across all self-regulatory organizations.

The Commission is publishing the notice under Section 19(b)(1) of the Securities Exchange Act of 1934 and Rule 19b-4 to solicit comments. The operative date will be set in coordination with the other SROs and the Commission once the amendment is deemed operationally and technologically feasible. Notice to customers will be issued via Trader Alert.

The filing cites Section 6(b) of the Act and Section 6(b)(5) as statutory authority, emphasizing that the amendment promotes "just and equitable principles of trade" and protects investors by preserving market stability during extreme price declines.