Nasdaq PHLX abandons CORE FIX after failing to generate participant interest

Nasdaq PHLX has filed to take CORE FIX out of its equities rulebook. In a notice dated 6 Nov and published in the Federal Register on 12 Nov (Release No. 34-106840, SR-PHLX-2026-65), the exchange said: “In spite of its best efforts, the Exchange has been unable to generate interest in CORE FIX among Exchange Participants. Therefore, rather than deploy an order entry protocol that Participants are not even interested in testing, the Exchange proposes to abandon its plans to deploy CORE FIX.”

The filing, made on 30 Oct, would “eliminate all references to CORE FIX that are currently present in Equity 4,” in Rules 3100 (Limit Up-Limit Down Plan and Trading Halts on PSX), 3301A (Order Types), 3301B (Order Attributes) and 3307 (Processing of Orders). It became effective on filing under Section 19(b)(3)(A)(iii) and Rule 19b-4(f)(6). Unless the Commission designates a shorter period, it does not become operative until 30 days after the filing date. Comments are due by 3 Dec. The Commission may temporarily suspend the change within 60 days of filing.

“The proposed rule change will not alter the operation of the Exchange’s market, the treatment of orders, or the rights or obligations of Participants,” Nasdaq PHLX said, because “CORE FIX has not been deployed on the Exchange.” “The Exchange notes that it will continue to offer all the order entry protocols that are currently available and operative on the Exchange—namely, OUCH, RASH, FLITE, and FIX.” Removing the CORE FIX references, it said, “will avoid confusion among Participants and other market participants regarding the protocols available for order entry” and “will allow the Exchange to better allocate its technological development resources.”

A protocol added in 2025, delayed twice, never launched

Nasdaq PHLX added CORE FIX to Equity 4 in September 2025, “in anticipation of making this new order entry protocol available to Exchange Participants in October of 2025.” In December 2025 it extended the implementation date to the first quarter of 2026, and in March 2026 it extended it again, to the end of 2026. An August 2026 filing added an online rulebook disclaimer that “References to “CORE FIX” will be implemented in 2026,” which this filing would also delete.

In the original September 2025 notice (Release No. 34-104020, SR-PHLX-2025-46), Nasdaq PHLX described CORE FIX as a new proprietary order-entry protocol that “will operate as a streamlined alternative to FIX for participants that utilize and appreciate the familiarity of coding for FIX, but do not utilize routing strategies.” It said CORE FIX would “allow participants to code to the standard FIX specifications, while gaining faster direct access to the Exchange along with the latest and most efficient order handling functionality that the Exchange has to offer,” and that “eliminating the intricate RASH-based software layer that provides for Order routing functionality, will streamline order handling behavior and improve Order latency relative to either FIX or RASH.” Orders entered through CORE FIX were to behave similarly to orders entered through OUCH for a range of order types on the PSX Book. The exchange said it would announce the implementation date in an Equity Trader Alert at least 30 days beforehand.

That 2025 filing also said the proposal was “not novel,” because The Nasdaq Stock Market and Nasdaq BX had “made similar changes to their rulebooks to establish CORE FIX on their equities markets,” with “substantially similar” functionality. The 12 Nov notice does not discuss those venues.

Fee-schedule clean-up already on file

A separate filing, SR-PHLX-2026-66 (Release No. 34-106781), was made on 22 Oct and published in the Federal Register on 4 Nov. In it, Nasdaq PHLX said it had filed, on 22 Oct, “a proposal, with immediate effectiveness, to abandon plans to deploy the CORE FIX order entry protocol,” and proposed to “delete from its equities fee schedule (PHLX Equity 7) all references to CORE FIX, which had been added to the fee schedule in anticipation of testing and deploying CORE FIX.” Those references included a CORE FIX port fee of $400 per month per port, a disaster-recovery port fee of $25 per month per port, and CORE FIX Testing Facility ports. The exchange said the deletions “will not change the availability, pricing, or functionality of any service currently used by members.”

The 12 Nov Equity 4 notice points to that fee filing and does not amend Nasdaq PHLX’s other 12 Nov fee notice, which streamlines displayed-liquidity credits on Nasdaq PSX and is a separate proposal.

Why it matters

Analysis. Connectivity changes usually add a port, delay a launch, or tweak a fee. This one takes a protocol back out of the rulebook and says, in terms, that members would not even test it. After a planned October 2025 start and two subsequent delays, CORE FIX on Nasdaq PHLX never became a live order-entry path. Firms already wired to OUCH, RASH, FLITE or FIX do not have to recode, and no production port is being switched off.

The 2025 filing had presented CORE FIX as a faster, FIX-coded, non-routing alternative that would behave like OUCH. Whether that design failed to interest users, or whether the demand was never there on Nasdaq PHLX, is not something these notices measure. They only record the outcome and the remaining protocol set. The 2025 notice’s comparison with CORE FIX on The Nasdaq Stock Market and Nasdaq BX is also left untouched: those venues are not part of the 12 Nov filing.

What we are watching

• Whether The Nasdaq Stock Market or Nasdaq BX, which Nasdaq PHLX said in 2025 had already added CORE FIX, make any change of their own.
• The 3 Dec comment deadline on SR-PHLX-2026-65, and the date on which the Equity 4 deletions become operative.

Sources

• Release No. 34-106840 (SR-PHLX-2026-65): Notice of Filing and Immediate Effectiveness of a Proposal To Amend Equity 4 To Remove All References to the CORE FIX Order Entry Protocol, U.S. Securities and Exchange Commission, notice dated 6 Nov 2026, published in the Federal Register on 12 Nov 2026
• Release No. 34-106781 (SR-PHLX-2026-66): Notice of Filing and Immediate Effectiveness of a Proposed Rule Change To Amend the Exchange’s Transaction Fees at Equity 7, Section 3, To Delete Obsolete References to the CORE FIX Order Entry Protocol, U.S. Securities and Exchange Commission, notice dated 30 Oct 2026, published in the Federal Register on 4 Nov 2026
• Release No. 34-104020 (SR-PHLX-2025-46): Notice of Filing and Immediate Effectiveness of Proposed Rule Change To Amend PHLX Equity 4, Rules 3100, 3301A, 3301B, and 3307 To Add the CORE FIX Order Entry Protocol, U.S. Securities and Exchange Commission, notice dated 23 Sep 2025, published in the Federal Register on 26 Sep 2025