Cboe BZX Aligns Trading Definitions with New Round Lot Rules
Published Date: 11/20/2025
Notice
Summary
Cboe BZX Exchange is updating its trading rules to match a new official definition of a 'round lot'—basically, the standard number of shares in a trade. This change affects traders and brokers using the exchange and takes effect immediately, with no extra costs involved. It’s all about keeping things clear and consistent so trading runs smoothly!
Analyzed Economic Effects
2 provisions identified: 2 benefits, 0 costs, 0 mixed.
Round Lot Becomes Price-Based
If you trade on Cboe BZX, the definition of a 'round lot' will change from a fixed 100 shares to a price-based size effective November 3, 2025. Under Rule 600 of Regulation NMS a round lot will be: 100 shares for stocks with average closing price $250.00 or less; 40 shares for $250.01–$1,000.00; 10 shares for $1,000.01–$10,000.00; and 1 share for $10,000.01 or more. The round lot assignment is recalculated semiannually using a one-month Evaluation Period (March for May assignments; September for November assignments).
Rulebook Language Updated for Clarity
Cboe BZX will update related Exchange rules to remove fixed share references and instead reference the new round lot definition on November 3, 2025. For example, phrases like 'one hundred (100) shares' and the reference to 'five round lots' usually being '500 shares' will be replaced so 'normal unit of trading' means the round lot defined in Exchange Rule 11.10. The change is intended to reduce confusion for Exchange Members and the public.
Personalized for You
How does this regulation affect your finances?
Personalize government policy and PRIA will tell you what this federal register document means for your household, plus every other regulation we track. PRIA reads each provision against your financial profile to show you exactly what matters to your wallet.
Key Dates
Department and Agencies
Related Federal Register Documents
2026-20466, Adviser and Regulated Fund Custody Rules; Crypto Custody Rules
The SEC is updating rules for how investment advisers and funds handle crypto assets, making sure they keep these digital investments safe and properly reported. These changes affect advisers, funds, and anyone managing crypto securities, aiming to modernize rules and improve transparency. Comments on the proposal are open until December 7, 2026, so get ready to weigh in!
2026-19260, Rescission of Rule 14a-8's Federal Regulation of Shareholder Proposals and Amendments to Rule 14a-4
The SEC wants to stop its federal rule that controls how shareholders can make proposals at company meetings, letting state laws and company rules take over instead. They’re also changing rules so companies can sometimes vote on proposals not in their official materials—but shareholders can opt out if they want. This affects investors and companies, with comments open until November 20, 2026, and could shake up how shareholder voices are heard and counted.
2026-18424, Political Contributions by Certain Investment Advisers
The Securities and Exchange Commission (the "Commission" or the "SEC") is proposing to rescind the political contribution rule under the Investment Advisers Act of 1940 (the "Advisers Act"), which prohibits investment advisers from providing investment advisory services for compensation to a government client for two years after an adviser or any covered associate of the adviser makes a contribution to certain categories of elected officials or candidates, among other prohibitions. In the more than fifteen years since the rule was adopted, implementation challenges associated with the political contribution rule have resulted in a range of significant unintended consequences, including compliance practices among some investment advisers that may have had the effect of restricting all political contributions by the investment advisers and their employees. Market participants also have stated that the political contribution rule is burdensome, complex, and both lacks clarity and creates a de facto strict liability standard. The Commission is of the view that other existing requirements of the Advisers Act and its associated rules, including prohibitions on fraud, fiduciary duty requirements, the compliance rule, and the code of ethics rule (defined below), are likely sufficient to address pay-to-play practices while allowing an adviser the flexibility to implement an approach that is more appropriately tailored to its particular risks, rendering the political contribution rule unnecessary. The Commission also is proposing to amend the rule under the Advisers Act pertaining to books and records consistent with the proposed rescission.
2026-18190, Transfer Agent Rules
The U.S. Securities and Exchange Commission ("SEC" or "Commission") is proposing to adopt new rules, amend existing rules, amend the existing form for registration with the Commission as a transfer agent (Form TA-1) and the existing form for reporting activities of transfer agents (Form TA-2), and rescind an existing rule governing registered transfer agents. The proposals are designed to modernize the rules governing registered transfer agents.
2026-17183, Regulation Crypto Assets
The Securities and Exchange Commission ("Commission") is proposing new rules to create a tailored offering regime for certain investment contracts involving crypto assets. The proposed offering regime is intended to facilitate capital formation and accommodate innovation within the crypto asset markets while, at the same time, ensuring that investors are adequately protected and provided with the information they need to make informed investment decisions. The proposed rules would be set forth in a new regulation titled "Regulation Crypto Assets" and would include two exemptions from the registration requirements of section 5 of the Securities Act of 1933. The first exemption would permit offerings of up to $5 million during a four-year period. The second exemption would permit offerings of up to $75 million during each 12-month period. Under both exemptions, issuers would be required to make certain principles-based narrative disclosures available to their investors. In addition, issuers under the second exemption would be required to provide financial statements and would be subject to ongoing reporting requirements. Issuers that rely on these exemptions would remain subject to the antifraud and antimanipulation provisions of the Federal securities laws. The proposed rules also would include a conditional safe harbor from the term "investment contract" in the definitions of "security" in the Securities Act of 1933 and the Securities Exchange Act of 1934. If the conditions of that proposed safe harbor are satisfied, then a crypto asset would be deemed not to be subject to an investment contract for purposes of those definitions of "security."
2026-12163, The Trade-Through Rule and Locked and Crossed Markets Provisions of Regulation NMS
The SEC wants to scrap some old rules that stop stocks from being traded at worse prices and prevent confusing market quotes. This change affects stock traders and exchanges, aiming to simplify trading and possibly speed things up. If you want to share your thoughts, you’ve got until August 17, 2026, so don’t miss out!
Previous / Next Documents
Previous: 2025-20390, Self-Regulatory Organizations; Cboe BYX Exchange, Inc.; Notice of Filing and Immediate Effectiveness of a Proposed Rule Change To Amend Exchange Rule 11.10, Units of Trading, To Conform With the Amendment to the Definition of Round Lot Under Rule 600 of Regulation NMS
Cboe BYX Exchange is updating its trading rules to match a new official definition of a 'round lot'—basically, the standard number of shares in a trade. This change affects traders using the BYX Exchange and kicks in right away, with no extra costs involved. It’s a smooth move to keep things clear and consistent for everyone trading stocks.
Next: 2025-20392, Self-Regulatory Organizations; Fixed Income Clearing Corporation; Notice of Filing of Partial Amendment No. 1 to Proposed Rule Change To Establish a New Collateral-in-Lieu Offering Within the Sponsored GC Service, and Expand the Sponsored GC Service To Allow a Sponsoring Member To Submit for Clearing a “Done-Away” Sponsored GC Trade
The Fixed Income Clearing Corporation (FICC) is adding a new option called Collateral-in-Lieu to its Sponsored GC Service, letting members use different types of collateral. They’re also expanding the service so members can clear special “done-away” trades more easily. This change affects financial firms using FICC’s services and aims to make trading smoother, with no extra costs announced yet.