MEMX Secures Immediate Rule Change to Preserve 4 a.m. Post-Halt Resumption

On August 28, 2026, MEMX LLC filed a non-controversial proposed rule change with the Securities and Exchange Commission, and the Commission published a notice of filing and immediate effectiveness on September 8, 2026 (Release No. 34-106293; File No. SR-MEMX-2026-29). The proposal amends Rule 11.23(b)(2) of the Exchange's rules, which governs the resumption of trading after a Level 3 market-wide circuit breaker halt.

The amendment is intended to retain the Exchange's current 4 a.m. ET resumption time following a Level 3 halt, even after MEMX expands its trading schedule to a 23-hours-per-day, five-day-week model. The new Overnight Trading Session, slated to begin on December 6, 2026, will run from 9 p.m. to 4 a.m., but the proposed rule change prevents an earlier, 9 p.m. restart that the existing language would otherwise require.

Specifically, MEMX proposes to delete the language that halts trading "for the remainder of the trading day" and replace it with language that hard-codes a 4 a.m. resumption on the following trading day. The change does not alter the underlying market-wide circuit breaker mechanism; it merely aligns the resumption timing with current practice across U.S. equity exchanges.

The Exchange cites Section 6(b) of the Securities Exchange Act of 1934 as the statutory basis, emphasizing the goal of preserving a cooling-off period that supports market stability and investor confidence. MEMX notes that other self-regulatory organizations, including FINRA, are expected to file comparable amendments to maintain harmonized rules.

The notice invites comments from interested persons, with the filing docket available online at https://info.memxtrading.com/regulation/rules-and-filings/.