$50%-Plus off-exchange trading puts stock rules in doubt

In Washington, the Securities and Exchange Commission is proposing to pull back some of the guardrails that have shaped how stock orders move for two decades. The agency says the 2005 framework for National Market System, or NMS, stocks was built for a market that has since become highly automated, interconnected, fast and competitive, with off-exchange trading now regularly topping 50% of overall volume.

At the center of the proposal is Rule 611, the trade-through rule that helps steer orders toward the best available price across venues. The SEC wants to rescind that rule for NMS stocks, along with the ban on locked and crossed quotations, where one market’s bid and another’s offer overlap in a way the current rulebook tries to prevent.

A market built for a different era

The commission’s argument is not that price matters less now. It is that the machinery around price discovery has changed enough that the old protections may not be doing the same work they once did. Since the rules were adopted, the agency says, trading has become more fragmented and far more electronic, and market participants have broader, faster access to information across venues.

That matters because broker-dealers, market makers and exchanges have built systems around the current routing rules. Those systems are designed to help orders reach the best available price, but the SEC says the same technology that made the market faster has also made the 2005 restrictions less useful as a practical matter.

What changes for traders

If the proposal becomes final, firms would have to adjust the plumbing that decides where orders go and how quotes are handled. The SEC is also proposing conforming changes to related definitions and provisions tied to the current framework.

For retail investors, the effect would be less visible than it sounds. A stock order still has to find a price and a venue. The real question is whether removing these rules would make that process cleaner in a market that already relies heavily on routing technology, or leave more of the burden on firms’ own systems and execution choices.

A public test of the new theory

The SEC is framing the rewrite as modernization, not a technical cleanup. It is asking whether the stock market’s old protections still serve investors in a world where trading is faster, more automated and increasingly done away from the exchanges that once dominated the market.

Comments on the proposal are due Aug. 17, 2026.