1. The Four Core Mandates of Supplementary Material 5310.09
FINRA Rule 5310 (Best Execution and Interpositioning) requires broker-dealers to use reasonable diligence to ascertain the best market for a security and buy or sell so that the resultant price to the customer is as favorable as possible under prevailing market conditions. When a firm routes customer orders to other broker-dealers for execution on an automated, non-discretionary basis, or internalizes customer orders, Supplementary Material 5310.09 governs its supervisory obligations. Under 5310.09, broker-dealers must conduct a regular and rigorous review of execution quality.
The rule enforces four foundational requirements. First, frequency: reviews must occur at least quarterly, with more frequent evaluations warranted during high volume or volatile periods. Second, granularity: the review cannot be performed on aggregate order flow, but must be segmented security-by-security (such as S&P 500 proxy holdings vs. non-S&P 500 NMS securities), order-type-by-order-type (market, marketable limit, non-marketable limit), and order-size-by-order-size across round lots and odd lots. Third, comparative benchmarking: firms must compare their current execution venues against competing market centers to which they do not currently route. Fourth, action mandate: if a material difference in execution quality exists, the firm must modify its routing arrangements or document contemporaneous written business justifications.
2. The Eight Mandatory Evaluation Factors Under 5310.09(b)
When comparing existing execution destinations against competing alternatives, Rule 5310.09(b)(1)–(8) specifies eight factors that broker-dealers must evaluate: price improvement; price disimprovement; execution likelihood for non-marketable limit orders; execution speed across latency distributions; execution size relative to displayed quotes; transaction costs and net execution fees; customer needs and instructions; and economic incentives or conflicts of interest such as payment for order flow (PFOF) and exchange rebates.
Public regulatory filings provide empirical baselines for several of these factors. SEC Rule 606 disclosures establish disclosed routing percentages and PFOF receipts, while Amended SEC Rule 605 reports publish execution quality across 24 notional order size tiers and eight execution speed buckets (allowing identification of p50, p95, and p99 speed tiers). However, public 605 and 606 data cannot observe trade-level arrival slippage or specific customer routing instructions. The public dossier covers the competing-markets comparison in FINRA Rule 5310.09 from public 605/606 data, while your firm's own order-level review remains required.
3. Why Executing Broker and Clearing Reports Leave an Evidentiary Gap
Broker-dealers often receive quarterly execution quality reports from their clearing firm or primary executing wholesaler. While these packets report metrics for orders routed to that specific counterparty, they contain zero data regarding market centers to which that firm does not route. Reviewing only where you currently route fails the comparative standard of Rule 5310.09(b).
Under FINRA Rule 3110 supervisory requirements, simply filing or downloading a clearing firm or wholesaler summary does not constitute an active supervisory review. Regulatory examiners inspect whether the firm's Best Execution Committee challenged anomalous results, compared execution quality against outside venues, and documented actionable determinations for identified shortfalls.
4. Quarterly Best Execution Committee Checklist
1. Data Gathering: Ingest quarterly Rule 606 routing disclosures (top 10 venues and any venue receiving 5% or more of non-directed order flow) and corresponding monthly Amended Rule 605 market-center files across all 24 notional and odd-lot tiers.
2. Competing-Market Comparison: Benchmark routed venues against competing market centers on identical symbol universes and order classes, identifying buckets where non-routed venues reported higher net price improvement or fill rates.
3. Economic Incentive Audit: Cross-reference venues paying PFOF or rebates against net price improvement delivered to customer orders to confirm execution quality was not subordinated to economic payments.
4. Committee Deliberation: Convene quarterly committee meeting with CCO, Head of Trading, and operational principals to review flagged exceptions.
5. Disposition Documentation: For every flagged shortfall, record either a concrete order routing modification or document written business justifications (e.g., clearing connectivity constraints, execution speed trade-offs, or commercial terms) in formal committee minutes.