Overview

SEC Rule 605 is a disclosure framework, not a single broker score. This chapter explains what its 2024 amendments change: larger customer-facing brokers with at least 100,000 accounts enter the reporting boundary, order sizes use notional categories, order types and executability are more detailed, and time-to-execution is measured more precisely. It then matches effective spread and price improvement to entry price, fill and cancellation data to completion, time buckets to speed, and realized spread to post-trade movement at stated horizons. Summary and detailed reports improve visibility, but differing order flow, market conditions, and customer populations still limit apples-to-apples rankings and do not establish best-execution compliance.

Learning outcomes

Rule 605 was designed for comparable execution-quality information, not a universal score.
Match each metric to its question: price, completion, speed, or post-trade movement.
The 2024 amendments add context, but order-flow differences still prevent automatic broker rankings or legal conclusions.

Keywords

Rule 605Effective spreadPrice improvementFill rateRealized spreadOrder flow

Reading Rule 605 Without Falling for a Single Score

The SEC’s Rule 605 is the public measurement layer for the retail execution problem. This chapter explains what the rule was built to compare, why its 2024 amendments add broker coverage and more detailed order categories, and how to match a metric to the question being asked. The practical outcome is a disciplined reading method: use Rule 605 to compare relevant pieces of an order lifecycle, but do not turn a summary statistic into a universal broker ranking or a legal finding about best execution.

The rule matters because execution quality is otherwise easy to describe selectively. A firm can highlight speed, price improvement, or a low spread number while leaving completion, order-flow mix, or the cost of unfilled shares outside the frame. Standardized reporting cannot eliminate every comparison problem, but it can make the questions and denominators visible.

What Rule 605 was designed to make visible

Rule 605, formerly known as Rule 11Ac1-5, has required market centers to publish standardized monthly execution-quality reports since 2000. Its purpose was not to produce a single score. It was to give investors and other market participants comparable information about how orders were executed, so competition could develop around implicit trading costs as well as explicit brokerage charges. The reports have also supported academic and market analysis of liquidity, order routing, and execution performance.

The market the rule first described is not the market investors encounter today. Trading has become faster, more automated, more fragmented across exchanges and off-exchange venues, and more heavily used by individual investors. The original reporting framework also used coarse share-size and order-type categories and measured time in a way that became less informative as execution speeds increased. The SEC’s 2024 amendments respond to that change by expanding who reports and by refining what is measured.

The most visible scope change is the inclusion of larger customer-facing brokers. A broker or dealer that introduces or carries at least 100,000 customer accounts through which NMS-stock transactions are effected must prepare Rule 605 reports. If a firm also operates as a market center, it must report the two functions separately. The threshold expands visibility into the broker side of the customer relationship, but it is a reporting boundary, not a quality judgment. A broker below the threshold is not thereby shown to have poor execution, and a broker above it is not thereby shown to have good execution.

The amended rule also expands the order population. Certain nonmarketable limit orders submitted outside regular trading hours can enter the report if they become executable during regular trading. Certain stop orders are included. Nonmarketable limit orders are treated from the point at which they become executable rather than from the moment they were first submitted while still out of reach. That distinction matters: measuring a patient order’s time from submission would charge it for time during which the market could not reasonably execute it.

Order size is no longer represented only by a number of shares.

Published by DeepMox

FAQ

What changed in the 2024 Rule 605 amendments?

The 2024 amendments expand broker coverage and order categories, add notional-size and fractional or odd-lot distinctions, refine executability and order types, and add a summary report.

Which Rule 605 metric should I use for price, completion, or speed?

Use effective spread and price improvement for executed-share price, fill and cancellation measures for completion, and time-to-execution for speed; use realized spread only to examine post-trade movement at its stated horizon.

Why can’t Rule 605 reports produce a fair universal broker ranking?

Firms handle different mixes of securities, order types, sizes, conditions, and customer populations; more detail improves comparison but does not make aggregate numbers apples-to-apples or prove best execution.

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How to Read SEC Rule 605 Reports

Reading Rule 605 Without Falling for a Single Score

What Rule 605 was designed to make visible

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