Could My Order Fill at a Worse Price if Rule 611 Is Repealed?

Possibly, for some orders, but nothing has changed yet. The SEC proposed on June 11, 2026 to rescind Rule 611 of Regulation NMS, the trade-through rule (Release No. 34-105655, File No. S7-2026-20). Comments closed on August 17, 2026, and as of October 2026 no final rule has been adopted, so Rule 611 currently applies. If the proposal were adopted, the SEC's own economic analysis says average execution quality for marketable retail orders would not be expected to change significantly, although some individual orders may receive worse prices.

Could a repeal let my order fill worse than the best quote on another exchange?

At the rule level, yes, that is what a repeal would allow. Today, during regular trading hours, every trading center, including an exchange, an alternative trading system or an off-exchange wholesaler that fills retail orders, must have procedures reasonably designed to prevent a trade at a price worse than a protected quotation on another exchange, unless an exception applies. The proposal would remove that prohibition entirely.

Whether your own order would actually fill worse is a separate question. In the economic analysis of the proposing release, the Commission writes on page 169 that rescinding Rule 611 is not expected to significantly affect average execution quality for marketable retail orders, "although some individual orders may receive worse prices."

None of this is in effect, since the SEC's file page for S7-2026-20 still lists a proposed rule with no final action. For what was proposed and on what timeline, see hi2morrow's overview of whether the SEC is repealing the trade-through rule.

What protects my price today, and what would remain?

Two layers protect the price of a stock order today, and only one of them is on the table. The first is Rule 611 itself, which applies only from 9:30 a.m. to 4:00 p.m. ET and in practice protects only the best round-lot quotes displayed by exchanges. Its exceptions include a one-second window for quotes that flicker, intermarket sweep orders, single-priced opening and closing transactions, and certain stopped orders.

The second layer is a broker's duty of best execution. FINRA Rule 5310 requires reasonable diligence to find the best market for a security so that the price a customer receives is as favorable as possible under prevailing market conditions. The release states on page 43 that this duty "will continue to apply regardless of whether Rule 611 is rescinded," and adds that a firm's commercial and competitive incentives should lead it to route to the best price at an away market when that is consistent with best execution.

In the SEC's framing, Rule 611 was built in 2005 as a backstop to that duty, and the proposal argues that today's automated, interconnected markets no longer need one. Whether best execution alone is enough is exactly where supporters and critics disagree.

What does the SEC's own analysis expect for retail orders?

The SEC expects little change on average and some risk for individual orders, especially larger ones. In footnote 175 of the release, the SEC notes that retail brokers route most of their customers' marketable orders to off-exchange wholesalers, which usually internalize them as principal, so most marketable retail orders never directly interact with protected quotes.

Because brokers tend to judge wholesalers by average execution quality measured against the NBBO, and because wholesalers often internalize those orders at prices better than the NBBO, the SEC argues on pages 169 and 170 that competition among wholesalers makes a significant change in average quality unlikely. The same pages contain the less comfortable finding. Commission staff analysis shows that wholesalers already sometimes trade through displayed odd-lot quotes, which Rule 611 does not protect, and the SEC acknowledges that after a repeal they "may begin to trade through displayed round-lot quotes," resulting in worse prices for those orders.

The SEC expects this effect to be limited, because brokers benchmark wholesalers against the NBBO, because larger orders usually fill better than walking the exchange book would produce, and because the amended Rule 605 reports add metrics that could expose such trades. Still, the release says that if wholesalers began trading through round-lot quotes, some larger marketable retail orders may receive worse prices, which "would transfer value from the retail investors to the wholesalers."

On size, footnote 615 offers the only reference point, and it is not a forecast for any particular order. In the Commission's analysis, off-exchange trade-throughs of 40-share odd-lot quotes raised transaction costs by 0.32 basis points, or 5.0% of a 6.34 bps effective spread, and the SEC suggests the cost of trading through a 100-share round-lot quote may be lower. On pages 171 and 172, the release adds that wholesalers could pass some of the gain back as extra price improvement on smaller orders, a form of cross-subsidization, though they might also keep part of it as profit. Order size already shapes fills for reasons unrelated to Rule 611, which hi2morrow's guide to why a stock order gets a bad fill explains.

What would that look like for an order in ABC?

Consider a hypothetical stock, ABC, at 11:05 a.m. ET on a regular trading day. The best protected offer is $30.00 for 300 shares on Exchange A, and the next price level is $30.02. A trader sends a marketable order to buy 100 shares, and the broker routes it to a wholesaler. Today the wholesaler cannot fill that order at $30.01 or $30.02 while the $30.00 offer stands, unless an exception applies, and in practice it usually fills at $30.00 or better, for example at $29.998 with price improvement.

If Rule 611 were rescinded, nothing in Regulation NMS would forbid a $30.01 fill in the same situation. The SEC reasons that wholesalers compete on execution quality measured against the NBBO, which makes them less likely to trade through a round-lot quote that sets it, but the release does not rule out a worse fill for an individual order. Here that would cost 100 × $0.01, or $1.00, more, an illustration of the possibility rather than a prediction.

A 2,000-share order shows why trade-throughs and worse prices are not the same thing. With only 300 shares offered at $30.00, a wholesaler today may fill the whole order outside the NBBO at a price that still beats walking the exchange book, while sending its own principal orders to take out the protected quotes so that it complies with Rule 611. In footnote 612, the SEC says that without the rule it might stop sending those orders, which would raise the number of trade-throughs but might not raise the customer's cost.

Could my resting limit order be traded through?

It could become more likely, although the SEC does not expect a significant effect. On page 172, the release says most retail non-marketable limit orders are indirectly displayed on an exchange, where they may currently qualify as protected quotes. If trade-through rates on displayed exchange orders rose after a repeal, those resting retail orders would be traded through more often as well.

Suppose your buy limit for 100 ABC at $29.99 is displayed on an exchange and is the best bid in the market. If another venue executes a trade in ABC at $29.98 during regular hours, that trade goes through your bid. Today it would be a prohibited trade-through unless an exception applied. Under the proposal it would be permitted at the rule level, and your order at $29.99 would simply remain unfilled while the stock changed hands below it.

The SEC's evidence comes from settings where Rule 611 already does not apply. In footnote 408, staff found average trade-through rates during regular hours of 0.3% for corporate stocks and 0.1% for ETPs, including the one-second look-back, compared with 0.5% and 0.5% in the pre-market session and 0.4% and 0.6% after hours. The SEC cautions that this may not show what a repeal would do, because some firms operate as if Rule 611 applied outside regular hours. Footnote 176 reports that unprotected odd-lot quotes inside the NBBO in high-priced stocks were traded through at rates of 1% to 5% on exchanges and 11% to 19% for off-exchange trades larger than one share. The release adds that more fills outside the NBBO or more traded-through limit orders could lead to investor confusion and more customer complaints.

Why do critics say best execution is not enough?

Critics argue that a repeal would remove an order-by-order protection and replace it with a looser standard. In its comment letter of August 17, 2026 in File S7-2026-20, the advocacy group Better Markets points out that there is no SEC rule imposing best execution on brokers, since the SEC proposed one in 2022 and later withdrew it. The group argues that FINRA's rule lets brokers assess routing quality "in the aggregate rather than on an order-by-order basis," and asks the Commission to withdraw the proposal.

According to the letter, several exchanges asked the SEC in 2025 to clarify best-execution expectations if Rule 611 were rescinded. Its second argument concerns the NBBO itself: if displayed quotes lose their protection, liquidity providers may quote less aggressively, and the letter quotes warnings that spreads would likely widen.

The SEC addresses the same risk on pages 167 and 168, conceding that a repeal could reduce displayed liquidity and, in theory, widen NBBO spreads, while saying it does not expect the effect to be significant. It also admits on page 166 that it cannot reasonably estimate how much order flow might move off exchange. The Commission has not yet decided between these positions.

How can I check my own fills, before and after any change?

The tools for checking fills already exist and do not depend on the outcome. Under the amended Rule 605, with a compliance date of August 1, 2026, brokers with 100,000 or more customer accounts publish monthly execution quality reports, including a summary report, as described in the SEC's Rule 605 FAQ. According to the release, those reports include size improvement relative to depth at the NBBO and the percentage of shares of marketable orders executed outside the NBBO, which are the metrics most likely to show any change.

For your own orders, Rule 606(b)(1) lets you ask your broker where your orders were routed during the previous six months and when they were executed. Comparing the execution price with the NBBO at the execution time, rather than the quote you saw when you clicked, is the fair test, and hi2morrow's guide to why a market order fills at a different price explains the timing issues behind that gap. As of October 2026, it is not known when the SEC will act, whether a final rule would match the proposal, or how brokers and wholesalers would adjust their routing.

Alexander Styopin's professional view: the SEC's distinction between the average order and the individual order is the part retail traders should take seriously. Averages can stay flat while larger orders absorb a small cost that nobody notices on a single trade, so the practical habit is to record your own fills against the NBBO now, while Rule 611 still applies, and to read your broker's Rule 605 numbers on orders outside the NBBO. If the rule goes, that baseline will show whether your fills changed better than any headline.

Educational material only. Not investment or legal advice. Order handling, margin, and settlement rules can vary by broker, account type, and jurisdiction.

Author: Alexander Styopin, hi2morrow analyst and economist with 25 years of experience in the US stock market