Exchanges and Market Structure: Rules and Plumbing — 2026-09-23

Top developments

4 sources

sec.gov

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SEC.gov | Rulemaking Activity

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SEC.gov | What

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SEC.gov | Rulemaking petition to further reduce the standard settlement cycle (currently T+1) for br

NYSE files rule change for Level 3 circuit breakers under 23-hour trading

On September 18, the SEC published a Federal Register notice of filing and immediate effectiveness of NYSE's rule change amending Rule 7.12 concerning the resumption of trading following a Level 3 market-wide circuit breaker halt — explicitly in connection with the industry's expansion of trading hours to 23 hours per day, five days per week. The filing matters for desk compliance teams tracking how halt-and-resume mechanics translate into an effectively round-the-clock US market.

Nasdaq files options rule amendments

Also on September 18, Nasdaq filed and immediately effectiveness-amended its rules at Options 7, Sections 1 and 2, per a Federal Register notice. Options market rule changes arriving alongside extended-hours equity trading rulemaking signal a broader plumbing overhaul across asset classes.

Ransomware attack shuts Nepal Stock Exchange for a day

On September 20, a ransomware attack on data centre operator Data Hub Pvt Ltd froze trading infrastructure for 72 of Nepal's 90 brokerage firms, forcing the Nepal Stock Exchange (NEPSE) to suspend the full September 21 session. Trading resumed on Tuesday, September 22, after the one-day outage. The incident is a reminder of single-point-of-failure risk at shared broker data centres and of regulators' willingness to halt entire markets to preserve fairness and security.

ICE–MarketAxess merger spread narrows

ICE stock closed at USD 155.47 on September 19, valuing the group at about USD 87.28 billion, while MarketAxess closed at USD 163.42 on Nasdaq on September 18 — about 2.2% below ICE's USD 167.00 cash offer — as investors position around the pending USD 5.7 billion fixed-income platform acquisition. The narrowing arb spread suggests market expectation of deal completion.

Local view

German-language coverage focuses on market prices rather than rulemaking: n-tv's daily Börsen-Tag reports the DAX starting firmly again on September 23, with Hong Kong property stocks (China Vanke +4.8%) in focus on a Reuters report of regulator intervention in the developer's debt. ad-hoc-news notes Deutsche Börse's own stock closed Xetra trading on September 22 at EUR 282.55 — the exchange operator's shares remain a proxy for European market-structure sentiment.

In Nepal, local outlets including The Himalayan Times, The Kathmandu Post and Nepalnews detail the NEPSE shutdown and recovery, with commentary focused on market resilience and data security of investor records.

Context & numbers

• ICE market cap ~USD 87.28 billion (September 19 close, USD 155.47); MarketAxess trades ~2.2% below ICE's USD 167.00 offer.
• Deutsche Börse shares closed at EUR 282.55 on Xetra, September 22.
• The Nasdaq Composite posted its first record close since June on September 21.
• NSE's IPO valuation debate puts global exchange multiples in frame: SGX ~34.3x PE, LSE 29.3x, Nasdaq 26x, HKEX 25.2x (September 17).

On the radar

• SEC comment period on the tokenized NMS stock "innovation exemption" — watch for venue applications under the five-year framework (flagged previously; follow-on filings are the fresh signal to track).
• NEPSE: further details on the ransomware attack's cause and any regulatory review of the shared broker data centre model.
• ICE–MarketAxess deal closing timeline; spread movement offers a live read on regulatory approval odds.
• Euronext CEO Stéphane Boujnah's previously announced departure in May 2027 — succession planning at Europe's biggest exchange operator will drive 2027 consolidation speculation.