When the benchmark becomes the rule

What the change implies

On June 11, 2026, the Securities and Exchange Commission (SEC) proposed to rescind Rule 611, the Order Protection Rule, and Rule 610(e), the locked and crossed markets provision, of Regulation NMS.¹ Rule 611 is the trade-through prohibition: a trading center generally cannot execute an order at a price inferior to a protected quotation displayed elsewhere, subject to narrow exceptions such as the intermarket sweep order (ISO).² For two decades that prohibition has made the national best bid and offer (NBBO) a regulatory anchor — the reference price against which routing is measured, and the reason an execution worse than the best displayed price is rare.³

Rescission removes the anchor, not the duty. The Commission's position is that best execution — the obligation to seek the most favorable terms reasonably available — can protect investors without the mechanical rule sitting on top.⁴ Commissioner Mark Uyeda, supporting the proposal, framed it as a beginning rather than an endpoint, one that unsettles long-standing assumptions and raises open questions about best execution, transparency, trading mechanics, and investor confidence.⁵ Comments are due August 17, 2026.⁶

The consequence for compliance is a shift in kind. A trade-through is a bright-line fact: an execution either printed through a protected quote or it did not, and a machine can test it. Best execution is a judgment: whether the route sought the best terms, weighed across price, size, speed, and cost. Take away the bright line, and the judgment has to be measured against something and shown. That something is the benchmark.

What a benchmark is, and why it now carries more

A benchmark is a reference price a firm measures an execution against. Two are standard. The arrival price is the market price at the instant an order reaches the desk; measured against it, a buyer wants to pay as little more as the market allows, and the gap records how much the order moved the price by being worked. The interval volume-weighted average price (VWAP) is the average price of every trade in the security while the order is worked, each weighted by its size; measured against it, a buyer wants to have paid less than the market's own average over the same window.

Alongside the benchmarks sit the execution-quality measures the SEC's own reporting rules define — effective spread, realized spread, price improvement relative to the quote, and time to execution.⁷ Together they answer the question the trade-through rule used to answer mechanically: did the customer get a good result, and can the firm show it?

Here is why the benchmark carries more weight after rescission. Today the trade-through rule keeps venues interconnected and quotes competitive, which is part of what makes the NBBO a reliable yardstick in the first place. Remove the rule, and some commenters question whether quoting activity, and with it the integrity of the NBBO, would weaken — which would soften the very reference the benchmark and the best-execution analysis lean on.⁸ The obligation to measure grows heavier at the moment its measuring stick loses some of its rigidity. A firm's answer is to make its benchmarks deliberate: chosen in advance, applied consistently, and never swapped after the fact to flatter a result.

The compliance that follows

Best execution does not merely survive rescission; it absorbs the weight the rule used to carry. Under Financial Industry Regulatory Authority (FINRA) Rule 5310, a firm must use reasonable diligence to find the best market and obtain a price as favorable as possible under prevailing conditions, and — where it does not review order by order — must conduct a regular and rigorous review of execution quality, at least quarterly, security by security and order type by order type.⁹ Three features of that duty matter more once the backstop is gone. The obligation cannot be transferred: when a firm routes customer flow to another for handling, both the routing firm and the receiving firm hold it.¹⁰ Conflicts must be confronted: payment for order flow (PFOF), rebates, and routing to affiliated venues cannot be allowed to interfere with the search for best terms.¹¹ And the review must be evidenced — the data considered, the routing decisions, and the rationale behind them, documented well enough to defend.¹²

Two parts of that compliance are large enough to stand on their own, and both are set out in the callouts below: the inventory a firm builds of everything its systems and policies still say about the old rule, and the record by which a single routing decision is defended once the rule is gone.

Rule 605 and 606: the disclosures become the proxy

With the mechanical rule removed, the public disclosures of execution quality and routing become the most visible proxy for best execution. Rule 605 requires standardized monthly reports of execution-quality statistics; the SEC's March 2024 amendments — the first substantive update since the rule was adopted in 2000 — expanded the reporting entities to include broker-dealers that introduce or carry 100,000 or more customer accounts, modernized the order-size and order-type categories to capture odd lots and fractional and larger orders, and refined the time-to-execution and spread metrics, with a compliance date now set at August 1, 2026.¹³ Rule 606 requires firms to disclose how customer orders are routed, including the financial arrangements — PFOF among them — that may bear on routing.¹⁴

The sequencing is contested. Commissioner Uyeda invited comment specifically on how execution quality and best-execution practices might evolve without the rule, and market participants have argued that any weakening of the trade-through prohibition should travel with stronger execution-quality and routing disclosure rather than ahead of it.¹⁵ For reporting and record-keeping teams, the practical point is plainer: after rescission, the Rule 605 and 606 reports are much of what an outside reader can see, so the numbers in them, and the routing behind them, have to withstand a reading they no longer share with a bright-line rule.

The shape of it

Rule 611 made one thing — price protection — mechanical and testable. Its removal does not lower the standard; it moves the proof. Best execution was always the underlying duty, but the trade-through rule stood in front of it as a rule a machine could check. Take the rule away, and the duty stands exposed, to be met against benchmarks chosen in advance and shown through a record built to be read back. The benchmark, in other words, starts doing the work the rule used to. That is the burden rescission quietly transfers — not lighter, only moved from the rule to the record.