MEMX proposes immediate amendment to Rule 11.15 covering overnight trades

On Oct. 19, 2026, MEMX LLC filed a proposed rule change with the Securities and Exchange Commission that is effective immediately, amending Rule 11.15 (Clearly Erroneous Executions). The filing appears in the Federal Register as FR Doc No. 2026-21926, Release No. 34-106727, File No. SR-MEMX-2026-33.

The amendment is intended to align the CEE review process with the Commission's August 5, 2026 approval of Overnight Protected Bands for 23/5 trading under the LULD Plan. By extending LULD-based restrictions to the Overnight Protected Hours (9:00 p.m. ET through 4:00 a.m. ET), the Exchange seeks to provide greater certainty that trades executed within those bands will stand.

Specifically, the proposal replaces the phrase "Regular Trading Hours" with "LULD Protected Hours," adds definitions for "Overnight Protected Hours," "Overnight Price Bands," and incorporates the Overnight Percentage Parameter into Rule 11.15(c)(1)(B). It also reverses the changes to Rule 11.15(c)(2)(A)-(D), (d)(3), and (f) that were made in MEMX's earlier 23/5 filing.

Classified as a "non-controversial" change under Section 19(b)(3)(A)(iii) of the Act, the proposal is open for public comment as required by Rule 19b-4. Interested parties may submit comments in accordance with the notice's instructions.

If adopted, the amendment will affect all market participants executing trades during the designated overnight session on MEMX, limiting the circumstances under which a transaction can be deemed clearly erroneous during those hours.