What U.S. post-trade regulation actually requires your systems to do.

Nine governing rules across six operational domains. One interlocking system.

Every section below goes deep on one domain. Start here to find the rules most relevant to your role.

• One interlocking system

  Post-trade regulation is often presented as a list of separate requirements. In practice, these rules share infrastructure. The books and records that 17a-3 requires creating are the same records that 17a-4 requires preserving, that 17a-5 requires auditing, and that 15c3-3 and 15c3-1 depend on being accurate in an authoritative System of Record. Settlement operations feed customer protection computations. Capital adequacy depends on position data that trade lifecycle management produces. Supervision governs all of it.

• Digital assets in every domain

  The six domains below are the operational vocabulary. The nine rules are the regulatory framework they live inside. In 2026, every domain now includes digital assets — not as a separate track, but as a standard column in the same table.

Settlement Cycle Compliance

Every covered securities trade must settle by T+1. That clock starts the moment the trade executes — and affirmation by end of trade date is what makes T+1 settlement structurally possible, and T+0 readiness operationally visible.

• 15c6-1 — The settlement clock

  SEC Rule 15c6-1 establishes that broker-dealers must not effect or enter into a contract for the purchase or sale of a covered security that provides for payment of funds and delivery of securities later than T+1 — one business day after the trade date. That is the legacy floor. Everything else in this section is about what must happen within trade date to make T+1 settlement structurally achievable — and what separates firms that are merely T+1 compliant from firms whose operations are built for the compressed settlement cycles that follow.

• 15c6-2 — What must happen by end of trade date

  SEC Rule 15c6-2 requires that broker-dealers establish, maintain, and enforce written policies and procedures reasonably designed to ensure that the allocation, confirmation, and affirmation of a covered trade is completed as soon as technologically practicable and no later than the end of trade date. The phrase "as soon as technologically practicable" is operative and forward-looking. For digital assets and on-chain settlements, the smart contract signature at point of execution is the affirmation — there is no 9:00 PM cutoff because settlement finality is computed at the moment the contract executes. A firm that achieves end-of-day affirmation through manual triage is increasingly viewed in a 2026 audit context as having a written supervisory procedures deficiency. Compliance requires Deterministic Enrichment: pulling from a Reference Data Master, without human lookup latency in the critical path.

• The DTCC operational framework

  DTCC's infrastructure implements the 15c6-2 requirement through specific operational cutoffs — including an allocation cutoff and a Same-Day Affirmation (SDA) cutoff, currently 9:00 PM ET, on trade date. These deadlines are DTCC's operational implementation of the requirement, not rule text. Firms should confirm current DTCC deadline times directly from DTCC operational documentation.

• The compliance-to-settlement gap

  Affirmation satisfies Rule 15c6-2 — but affirmation is not the end of the pipeline. An affirmed trade must still generate a settlement instruction. In an ISO 20022 workflow, that means producing a sese.023 message within the instruction submission window. If the sese.023 is generated as a scheduled batch job rather than as a real-time trigger on the affirmation event, a trade affirmed just before the SDA cutoff may miss the submission window entirely. This gap — the Instruction-to-Affirmation Latency — is where compliant trades fail to settle. Operational compliance is achieved through a pipeline where the sese.023 is triggered by the affirmation event as a real-time output, not a downstream batch artifact.

• The Pre-Noon Resolution Alpha

  The period before approximately 12:00 PM ET on trade date is operationally significant. After this point, cancellations and amendments to trades in DTCC's infrastructure become significantly more complex. A trade carrying an enrichment error — a missing or incorrect standing settlement instruction, an unmatched allocation — that is not identified before noon requires a more involved resolution path than the same error caught in the first hours of trading. Operational compliance with Rule 15c6-2 is meaningfully easier when trade enrichment is complete early in the trading day.

• What settlement failure looks like in the U.S.

  A trade that misses affirmation by end of trade date carries elevated settlement failure risk. For equity securities subject to Regulation SHO, Rule 204 requires broker-dealers to close out a failure to deliver by a defined date. For other covered securities, a counterparty that does not receive delivery on T+1 has the right to initiate a buy-in. There is no CSDR-equivalent daily cash penalty for settlement failure in the U.S. framework — consequences operate through buy-in mechanics, capital treatment of aged fails, and Regulation SHO close-out obligations. Settlement failures that are not resolved quickly extend into customer asset protection and net capital — that chain is covered in the next two sections.

Customer Asset Protection

Broker-dealers must keep customer assets separate and accounted for at all times. Settlement operations are where that obligation becomes structurally achievable — or where it quietly breaks down, one aging position at a time.

• The reserve requirement

  SEC Rule 15c3-3 requires broker-dealers to maintain a special reserve bank account, for the exclusive benefit of customers, funded with cash or qualified securities equal to the net amount owed to customers as computed by the reserve formula (Exhibit A). The formula nets customer credit items — what the firm owes customers — against debit items — qualified offsetting amounts, reduced by a mandatory buffer of approximately 3% for weekly filers. Where credits exceed debits, the net must be deposited by the close of the next business day.

• Daily computation for large firms

  Most broker-dealers run the reserve computation weekly. Under a 2024 SEC amendment, carrying broker-dealers with $500 million or more in average total credits are required to compute the reserve formula and make required deposits daily. For firms at or approaching this threshold, the distinction between intraday reserve monitoring as a best practice and as a regulatory mandate is narrowing.

• The possession and control requirement

  Broker-dealers must maintain possession or control of all fully paid and excess margin customer securities. Securities held at DTC, at satisfactory control locations, or in transit under the rule's defined conditions are considered in possession or control. When securities are in transit, a clock starts.

• The in-transit clock — where settlement and customer protection connect

  Under SEC Rule 15c3-3(c)(6), securities that have been in transit for more than five business days are no longer considered in the firm's possession or control. They are treated as a short position in the reserve formula: the firm owes customers the value of those securities but cannot demonstrate it holds them — increasing the required reserve deposit. A trade that fails to settle keeps the security in transit. After five business days, that in-transit position becomes a non-control item in the reserve formula. The result is not merely an unresolved trade — it is a computable deficiency between the firm's actual reserve balance and the balance the rule requires.

• Digital assets and possession and control

  For digital assets operating under the post-SAB 121 regulatory landscape, the same possession and control standard applies. The SEC's 2025 crypto asset guidance confirms that digital assets held for customers are subject to the same segregation and control obligations as securities held at DTC. The "control location" for an on-chain asset is the wallet or ledger that holds it — and demonstrating control means proving, with the same definitiveness as a DTC statement, that the asset is where it is supposed to be and has not moved. In a T+0 environment, waiting until day six to flag a possession and control exception is operationally untenable.

• The reserve formula — what feeds it

  The Exhibit A computation depends on data that must be current and reconciled. Account classification is a structural element frequently overlooked: general partners, directors, and principal officers are classified as non-customers. For digital assets, wallet and ledger accounts must be correctly classified — customer wallets, proprietary wallets, and omnibus accounts each require distinct treatment. A position record that is incorrect because of an unreconciled break flows directly into an inaccurate reserve formula computation.

• What a reserve deficiency triggers

  If the reserve computation shows that the required deposit exceeds the current balance, the broker-dealer must fund the deficiency by the close of the next business day. If a broker-dealer fails to make a required deposit, it must notify the SEC and its designated examining authority immediately — by the fastest available means. A written explanation of the cause and planned remediation is typically required within 24 hours of that initial notification, but the notification itself cannot wait. A deficiency that is discovered through the firm's own controls and reported promptly is a different regulatory event than one discovered on examination.

Capital Adequacy

Net capital must be maintained at all times — including intraday. An aged fail doesn't stay on the settlement ledger. It moves to the capital ledger at T+6, and the early warning threshold is 120% — not zero.

• The requirement

  SEC Rule 15c3-1 — the Net Capital Rule — establishes that every broker-dealer must maintain net capital no less than the greater of: the minimum dollar amount applicable to its business type, or its ratio requirement. Most broker-dealers operate under the Aggregate Indebtedness Standard (aggregate liabilities cannot exceed 1,500% of net capital) or the Alternative Standard (net capital must be at least 2% of aggregate debit items). Net capital is computed as net worth, minus non-allowable assets, minus haircut deductions on securities positions, minus operational charges including aged-fail deductions.

• "At all times" — what that phrase actually requires

  The phrase is operative. Net capital must be maintained before, during, and after taking proprietary positions — including intraday. SEC Rule 17a-11 — the Early Warning Rule — requires notification when net capital falls below 120% of the applicable minimum, or when the Aggregate Indebtedness-to-Net-Capital ratio exceeds 1,200%. The early warning threshold is not an operational comfort buffer — it is a mandatory notification trigger that precedes an actual deficiency. The operative monitoring target is "stay above 120% of minimum, and know the moment you approach it." A firm running overnight batch position snapshots cannot demonstrate this.

• Haircuts — where the capital charge lives

  Securities positions are reduced by haircut percentages applied to market value. Standard haircuts: equities typically 15%; concentrated positions 30%; fixed income varies by maturity and credit quality. For non-security digital assets not specifically approved by the SEC for a lower haircut, the haircut is 100% — the entire market value of the position is deducted from net capital. Under the GENIUS Act (enacted July 2025, effective date pending implementing regulations), qualified payment stablecoins may be treated as cash equivalents with a haircut of 0% to 2%. The difference between a 0% haircut and a 100% haircut on a $10 million stablecoin settlement position is $1.5 million in allowable net capital.

• Aged fails — the T+6 capital trigger

  A trade that fails to settle does not immediately generate a capital deduction. The capital charge mechanism under SEC Rule 15c3-1(c)(2)(ix) is time-triggered: a fail-to-deliver outstanding for five business days or longer (21 business days for municipal securities) generates a required capital deduction — effectively T+6 from settlement date. A firm with an Intraday Net Capital Monitor that ages open fails continuously and projects the T+6 capital impact is managing proactively — it has five days to resolve the fail before the capital charge materializes. Multiple concurrent fails during a period of operational stress can breach the 120% early warning threshold faster than a weekly batch report can surface them.

• The digital asset capital management problem

  For broker-dealers building digital asset businesses, price volatility is higher — a digital asset position within capital guidelines at market open may breach the 120% early warning threshold intraday. The approved / unapproved distinction must be tracked at the instrument level: two digital assets in the same wallet may carry different haircut treatments. Under the post-SAB 121 regulatory landscape, firms must evaluate control and legal segregation to determine whether digital assets held for customers must be reflected as a liability on the balance sheet. Real-time sub-ledger precision is not a digital asset operational enhancement — it is the prerequisite for the accounting analysis.

• What a net capital deficiency triggers

  A broker-dealer whose net capital falls below the applicable minimum must immediately notify the SEC and its designated examining authority. The Early Warning Rule requires notification at 120% of minimum — well before an actual deficiency. Under FINRA Rule 4120, a net capital deficiency can trigger a prohibition on business expansion. A deficiency discovered and addressed through the firm's own intraday controls is a different regulatory event than one discovered the next morning in a batch report.