A trading fee can look insignificant when expressed as a fraction of a cent per share. Across a high-volume business, however, eligibility for that fee can influence margins, customer pricing, and execution strategy. Understanding the conditions behind a discount is therefore a legal and operational issue as well as a finance exercise.

IEX’s latest filing provides an opportunity to examine those connections—and to review whether a firm’s assumptions about trading costs remain reliable.

1. The Change: A Higher Threshold, With an Exception

On October 6, the SEC published Release No. 34-106606 concerning IEX’s September 30 filing, SR-IEX-2026-40. Implementation is scheduled for November 1, 2026.

The general Incremental Fee Tier 2 threshold rises from 15 million to 20 million shares of prior-month eligible average daily volume above a member’s non-displayed baseline.

Those displayed tiers require prior-month displayed liquidity additions of at least 40 million and 50 million ADV, respectively. Sub-dollar trades remain excluded. www.sec.gov

Our assessment: firms should evaluate their displayed and non-displayed trading profiles together. A review limited to one activity category could miss an economically significant interaction.

2. Understanding the Inputs Before Modeling Costs

IEX’s fee schedule distinguishes eligible activity from broader non-displayed volume: the relevant fee codes are MI, MIB, TI, TIB, TIY, and TIYB.

The baseline averages eligible ADV in the three lowest-volume months between March 2025 and February 2026. Members joining after March 1, 2025 use their first three full trading months. IEX

For an operational team, the practical task is to build a reproducible calculation. Someone reviewing the result should be able to identify the source data, verify which executions were included, and trace the baseline used.

A dashboard showing total trading volume may be useful for commercial reporting but insufficient for fee reconciliation. Firms should avoid carrying a broad business metric into a calculation that requires a narrower set of inputs.

3. Qualification and the Final Invoice Are Separate Questions

Under the existing framework, the base fee is $0.0010 per share. The $0.0001 incremental rate is capped at one baseline for members without three consecutive qualifying prior months; sustained qualifiers receive a two-baseline cap, with excess incremental volume assessed at $0.0004.

Option 1 applies a prior-month blended rate to current eligible activity. Option 2 applies rates to current-month actual volume. Option 1 is the default absent an election. IEX

These mechanics suggest a two-stage review: establish eligibility, then calculate the invoice under the applicable option and caps. A cost forecast should preserve that distinction so a favorable headline rate does not become an assumption about every execution.

Finance teams should also reconcile forecast and realized costs by identifying the reason for a variance. A change in volume, an eligibility outcome, and a calculation-option effect require different responses.

4. Worked Examples: Translating the Framework Into Business Decisions

The following illustrations use simplified assumptions and are not forecasts of any member’s actual bill.

Eligibility Example

Assume a 10 million-share baseline and prior-month eligible ADV of 27 million. The increase is 17 million. That falls between the two thresholds above, making the displayed-tier exception decisive.

Cost Sensitivity Example

For 10 million shares assumed fully eligible for a given rate:

This arithmetic isolates the rate difference; it does not account for a baseline allocation, caps, or blended billing.

The useful budgeting question is how much activity can actually receive favorable treatment under the firm’s circumstances. A forecast should include a range of outcomes rather than treating one favorable month as a permanent operating condition.

5. The Regulatory Process: Immediate Effectiveness and Continuing Oversight

The filing became effective under Exchange Act Section 19(b)(3)(A)(ii). The SEC retains a 60-day window from filing to temporarily suspend it. Comments are due 21 days after Federal Register publication; the linked notice leaves the calendar date blank. Submissions should identify SR-IEX-2026-40. www.sec.gov

Exchange fee filings operate within an oversight framework. As the SEC explained in its 2023 volume-based pricing proposal, immediate effectiveness does not constitute Commission approval. Exchange pricing remains subject to statutory standards addressing reasonable fees, equitable allocation, unfair discrimination, and competition.

That historical proposal also identified potential routing conflicts: an intermediary’s incentive to achieve favorable pricing can diverge from a customer’s interest in execution quality. It is relevant background, rather than a statement that the proposal governs this filing. sec.gov

For firms reviewing this change, the governance question is whether trading incentives are understood and evaluated by the people responsible for execution oversight.

6. Practical Implications for Trading Firms and Their Customers

Broker-Dealers and Execution Providers

A useful review should bring finance, trading, compliance, and legal teams into the same discussion. Each sees a different part of the issue: the invoice, the execution decision, the control framework, or the customer commitment.

Teams should identify who owns the eligibility calculation, who approves changes to cost assumptions, and who reviews the impact of incentives on routing decisions. Clear ownership helps prevent an exchange update from becoming an unexamined system setting.

A practical internal discussion should address whether the firm can explain its pricing assumptions consistently across departments. If finance models one effective rate while an execution tool assumes another, the resulting discrepancy can affect both commercial decisions and management reporting.

Proprietary Trading Firms

For a firm trading its own capital, scenario analysis should test whether a strategy remains attractive when favorable fees are unavailable. Management should consider the economics of the strategy as a whole, including the cost of any operational changes proposed to improve eligibility.

The review should also distinguish organic growth in activity from trading undertaken to pursue a pricing benefit. That distinction can sharpen investment and risk decisions.

For example, a strategy that appears profitable under an optimistic fee assumption may warrant closer scrutiny if its projected margin narrows substantially under a less favorable scenario. The purpose of the exercise is to understand the strategy’s sensitivity before committing resources.

Institutional Customers and Firms Using Intermediaries

Customers reviewing broker pricing should ask how exchange fees and discounts are reflected in their arrangements. Relevant questions include who retains a discount, whether costs are passed through, and how adjustments are documented.

A customer does not need to reproduce every exchange calculation to request a clear explanation of the pricing methodology and the assumptions supporting it.

Contract language deserves particular attention where an arrangement refers to “actual exchange costs,” a fixed execution charge, or a negotiated cost estimate. Those formulations can produce different commercial outcomes. A review should establish what the parties intended and whether the agreement explains how changes are handled.

7. What to Review Before Implementation

A focused preparation process should cover five areas:

• Data: Confirm the baseline and eligible executions, and retain enough detail to reproduce the calculation.

• Forecasts: Model favorable and unfavorable outcomes, including the applicable caps and billing option.

• Systems: Check that fee assumptions used by reporting and execution tools reflect the intended implementation timetable.

• Contracts: Review cost pass-through provisions, pricing commitments, and any notice requirements for adjustments.

• Oversight: Document how commercial incentives are assessed alongside execution objectives.

These are review recommendations. They do not imply that every affected firm must change its contracts or trading strategy.

The objective is to identify where the change matters, determine who is responsible for responding, and make any necessary adjustments with a clear record of the underlying assumptions.

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This blog post is for informational purposes only and is not legal advice. Please consult with a Launch Legal attorney regarding your specific situation.