Why Your Broker Can't Skip a Better Price — For Now

Picture a farmers' market with seventeen stalls, all selling the same mangoes at slightly different prices. You spot one stall selling for a dollar less. Naturally, you want that mango. In the US stock market, there's a rule that has essentially said: if a better price is posted somewhere else, your broker should go get it. That rule is now on the chopping block. Let's start with the basics, because this one gets tangled fast.

What a trade-through actually is

A trade-through happens when one trading venue executes an order at a price worse than a better-priced quote that's already displayed somewhere else. Say Exchange A is showing a sell order at $29.99. If Exchange B lets someone sell at $30.00 without first dealing with that $29.99 quote, that's a trade-through. The better price got ignored.

The Order Protection Rule — formally Rule 611 of Regulation NMS, and informally the trade-through rule — was adopted in 2005 to stop exactly that. It requires every "trading center" (a term that covers exchanges, alternative trading systems, and brokers that execute orders internally) to have written policies reasonably designed to prevent trade-throughs of "protected quotations" in NMS stocks. NMS stands for National Market System — the framework that ties US equity markets together.

A "protected quotation" is narrow by design. It's generally the best bid or offer displayed on an exchange that's electronically accessible right away — the top of the book, in round lots. Think of it as the mango stall that's actually open for business, not the one with a handwritten sign and nobody at the counter.

Why the rule existed in the first place

The logic was straightforward. If you post a limit order — an order to buy or sell at a specific price — and someone can simply skip past it to trade at a worse price elsewhere, why would you ever post one? Displayed orders are the raw material of price discovery: the process by which the market figures out what a stock is actually worth. Protect the quotes, the thinking went, and people will keep posting them, spreads will stay tight, and everyone benefits.

The SEC also framed Rule 611 as a backstop to a broker's duty of best execution — the long-standing obligation to seek the best reasonably available terms for a customer's order. Importantly, the SEC was careful even in 2005 to say that complying with the trade-through rule did not by itself satisfy best execution. The rule was a floor, not a ceiling.

It was controversial from day one. It passed on a 3–2 vote, with then-Commissioners Paul Atkins and Cynthia Glassman dissenting at length. They argued it would constrain competition and innovation rather than help. Two decades later, Atkins chairs the SEC — and he hasn't changed his mind.

What regulators are proposing now

On June 11, 2026, the SEC voted to propose rescinding Rule 611 entirely, along with Rule 610(e), which requires exchanges and FINRA to have rules stopping members from displaying quotations that "lock" (a bid equal to the offer) or "cross" (a bid exceeding the offer) protected quotes elsewhere. Related definitions in Rule 600 would go too. Comments were due 60 days after Federal Register publication.

The SEC's stated reasons run roughly like this:

Markets changed. In 2005 there were about eight exchanges trading NMS stocks. Today there are 17 operating, with three more approved. Markets are automated, interconnected, and fast in a way they simply weren't then.

Costs added up. The SEC estimates a broker-dealer connecting to all exchanges spends roughly $5.7 million a year on market data and connectivity fees, and that onboarding a new exchange costs about $1.5 million with $200,000 in annual maintenance. Because a new venue could effectively guarantee itself connectivity revenue just by displaying a protected quote, the rule arguably subsidised venue proliferation and fragmented liquidity.

Large orders suffered. For institutions working a big "parent" order, the rule could force a detour to interact with a 100-share quote on some distant exchange before executing the rest — potentially signalling trading intent and increasing slippage, the gap between expected and actual execution price.

Complexity bred complexity. To comply with or navigate around Rules 611 and 610(e), the industry built specialised order types — intermarket sweep orders, price-to-comply, price-to-display, post-only — and elaborate routing logic. That's an arms race with paperwork.

Best execution can carry the load. The SEC argues that brokers' existing best execution duties under common law anti-fraud provisions and FINRA Rule 5310 remain sufficient protection.

The counterarguments worth taking seriously

Not everyone is convinced, and the pushback is substantive rather than sentimental.

SIFMA, the securities industry trade group, has described Rule 611 as the "head of an octopus" — move it and many other pieces of market structure move too. The National Best Bid and Offer, or NBBO, sits at the centre of that framework. It's referenced throughout SEC rules, exchange rules, and NMS plans, and it serves as the reference price for everything from execution-quality statistics to pegged and stop orders to short-sale price tests. Rule 611, in this view, supplied a practical floor under the quality of that benchmark: a quote that set the NBBO was generally a quote you could actually reach. Rescind the rule, and the NBBO stays — but that floor goes.

There's also the plain question Katten's analysis raises: is today's market interconnectedness the result of the trade-through rule? If mandatory order protection is what persuaded firms to connect everywhere, removing the mandate might lead them to connect to fewer venues. Whether quoting, and therefore the reliability of the NBBO, would suffer is genuinely unknown.

On locked and crossed markets, roundtable participants were largely aligned that locking shouldn't be prohibited, arguing the ban artificially widens spreads in tick-constrained stocks where the natural spread could be zero. Crossed markets drew more caution, with some concerned about retail investor confusion if crossed quotes get displayed.

Best execution drew the sharpest divide. One commenter likened enforcing it to "trying to nail Jello to a wall" — a vivid image, and not a flattering one for the safety net. FINRA's chief legal officer, Bob Colby, put it more diplomatically: best execution "is a powerful concept, but it operates within a market structure."

Even the commissioners aren't unanimous. Hester Peirce says she's been a skeptic since inception and that the rule "may be causing more mischief than good." Caroline Crenshaw urged caution, warning against treating rescission as "a magic bullet." The proposal also carves out listed options, which keep their own separate trade-through protections.

What this means if you're just investing

Honestly? For most retail investors, the practical difference may be invisible at first. Your broker still owes you best execution. Their smart order routers — the automated systems that scan venues in real time, weighing price, fees, fill probability, and latency — will keep doing their job, arguably with more discretion and less regulatory scaffolding.

What could change is the environment those routers operate in. If displayed quotes become less protected, fewer might get displayed, or venues might compete differently on speed versus price. The Vendor Display Rule question matters too: if locked or crossed quotes reach investor-facing screens without a prohibition, routing decisions get murkier and displays get harder to read.

One small irony worth noting: the SEC published its proposal to kill Rule 611 on 6/11 — a detail at least one law firm gave a wry hat tip. Whether that was deliberate, nobody's saying.

What's certain is that this is a proposal, not a done deal. Notice-and-comment rulemaking means it could be adopted, modified, or abandoned. Rules also differ by jurisdiction — this is US equity market structure, and nothing here settles what European or UK rules require. And nobody, including the SEC, can tell you today how markets would actually adapt.

What you can do is understand the machinery. Ask your broker what its execution policy says. Execution-quality reports exist for a reason. If the scaffolding comes down, knowing where the load-bearing beams are is worth something.