Form ATS-N/OFA Files Dataset

The Form ATS-N/OFA Files Dataset is a structured collection of every Order Display and Fair Access amendment filed on EDGAR by U.S. NMS Stock Alternative Trading Systems under Rule 304(a)(2)(i)(D) of Regulation ATS. One record corresponds to a single ATS-N/OFA accession — the seven-day notice an NMS Stock ATS files when previously disclosed information in Part III, Items 24 and 25 (Order Display and Execution Access) or 25 (Fair Access) of its effective Form ATS-N has become inaccurate or incomplete. Each record bundles the canonical EDGAR XML submission, an EDGAR-rendered XHTML view, any filer-supplied PDF redline exhibits, and a normalized metadata.json summary. The dataset is distributed as monthly ZIP containers and covers filings from August 1, 2022 onward, fully within the structured ATS-N XML era.

Dataset APIs

Dataset Files

What This Dataset Contains

The dataset captures Form ATS-N/OFA — the narrowest of the ATS-N amendment variants under Regulation ATS. ATS-N/OFA is reserved for situations in which information previously disclosed in Part III, Items 24 and 25 of an operator's effective Form ATS-N — the items addressing Order Display and Execution Access obligations under Rule 301(b)(3) and Fair Access compliance under Rule 301(b)(5) — has become inaccurate or incomplete and must be brought current within seven calendar days. The Commission makes the filing public upon receipt; ATS-N/OFA is not subject to the staff "no objection" review process applied to Form ATS-N initial filings or material amendments.

The form is filed electronically through EDGAR using the structured ATS-N XML schema, which renders the entire ATS-N document body as a structured tree even when the amendment touches only one or two items. Because the schema requires the full form body, every Form ATS-N/OFA filing technically restates all of Parts I, II, III, and IV alongside the cover-page narrative explaining the amendment, but the substantive change is typically isolated to a small set of fields and recapitulated in a free-text "statement about amendment" on the cover sheet.

The dataset folder structure is YYYY-MM/<accession-no-dashes>/.... The file types found in the dataset are XML, PDF, and JSON, and the container distribution is ZIP, partitioned by filing month. Form ATS-N was adopted by the Commission in 2018 and the ATS-N/OFA amendment variant has been filed exclusively through the structured EDGAR ATS-N XML schema since its inception, so format consistency across the dataset is high: every record contains an XML primary document conforming to the same schema, an XSL-rendered HTML companion produced by the same EDGAR stylesheet family (ATS-N_X01), and zero or more PDF exhibits. There is no ASCII/text or pre-XML legacy format for this form type, and no XBRL is used.

Content Structure of a Single Record

One record in the Form ATS-N/OFA Files Dataset is a single EDGAR submission of Form ATS-N/OFA — the Order Display and Fair Access Amendment to a previously effective Form ATS-N — identified by its 18-digit EDGAR accession number. Each record is materialized as a folder named after the dash-stripped accession number (for example 000179513125000008), nested under a YYYY-MM partition that corresponds to the filing month. The folder bundles the canonical EDGAR XML submission, an EDGAR-rendered XHTML view of the same submission, any exhibits filed alongside, and a normalized metadata.json summary describing the filing as a whole. Every record represents exactly one accession, and every accession represents one discrete amendment event filed by an NMS Stock Alternative Trading System.

Content layout of a single record

Inside one accession folder, the content is organized in three layers:

1. A normalized JSON summary, metadata.json, that flattens EDGAR header information about the filing.
2. The raw EDGAR submission, consisting of primary_doc.xml (the canonical XML body of the form) plus any filer-supplied exhibits, most commonly PDF redlines under names chosen by the filer (for example BOATS_EX3_FA_3.31.2025.pdf).
3. An EDGAR-generated XSL rendering of the same submission, located at xslATS-N_X01/primary_doc.xml, which is an XHTML 1.0 Strict document (despite the .xml extension) styled for browser and print display.

metadata.json

metadata.json is a flat JSON object describing the filing at the EDGAR-record level rather than item-by-item. Its fields are:

• formType — fixed at ATS-N/OFA for this dataset.
• accessionNo — the dashed accession number (e.g. 0001795131-25-000008).
• filedAt — ISO-8601 timestamp of EDGAR acceptance, with timezone offset.
• description — human-readable form description, typically including the amendment-type phrase.
• linkToFilingDetails — URL of the rendered filing on sec.gov.
• linkToTxt — URL of the complete submission text file (the SGML .txt envelope) on sec.gov.
• linkToHtml — URL of the EDGAR filing-index page.
• linkToXbrl — empty string, since ATS-N/OFA does not carry XBRL.
• documentFormatFiles — array of all documents in the submission, each entry carrying sequence, size, documentUrl, type (canonical EDGAR labels such as ATS-N/OFA for the primary document and ATS-N EX-3 REDLINE for redlined exhibits), and an optional description. The full submission .txt is also enumerated.
• entities — array of filer entities. Per-entity fields include cik, companyName (with role suffix such as (Filer) in parentheses), fileNo (the ATS file number, formatted 013-NNNNN), type, filmNo, act (typically 34 for Exchange Act), fiscalYearEnd as MMDD, and stateOfIncorporation as a two-letter code.
• id — opaque content-hash identifier.
• seriesAndClassesContractsInformation — empty for ATS-N/OFA filings.
• dataFiles — empty, reflecting the absence of XBRL or other structured data attachments for this form.

primary_doc.xml — the structured form body

primary_doc.xml is the canonical, machine-readable representation of the ATS-N/OFA submission. The root element is <edgarSubmission> in the namespace http://www.sec.gov/edgar/atsn, with the EDGAR common and atsncommon namespaces also imported. The document is split into two top-level branches: <headerData> (submission-level metadata) and <formData> (the form body itself).

<headerData>

The header carries submissionType (ATS-N/OFA), accessionNumber, and a filerInfo block containing the live/test flag, filer credentials (CIK and a redacted CCC), the ATS fileNumber (e.g. 013-00180), and submission-control flags such as overrideInternetFlag and confirmingCopyFlag. This block mirrors the EDGAR submission envelope and is distinct from the filer-entity descriptions surfaced in metadata.json.

<formData> element-naming convention

The form body uses Hungarian-style element-name prefixes that encode the type of input each field represents: tx* for short single-line text, ta* for free-form text-area prose, rb* for radio-button (Y/N) selections, and cb* for checkboxes. Item-level elements are named part<N>Item<X><suffix>, so an extractor can identify a field's section, item number, and input type from the element name alone. Conditional sub-items reproduce the parent's radio-button answer as an attribute on the wrapping element (for example <part2Item5aDoesOfferProductsAndServices rbPart2Item5aDoesOfferProductsAndServices="Y">), allowing branches to be interpreted without re-reading the parent.

<cover> — cover sheet

Contains the legal name of the NMS Stock ATS in txNMSStockATSName and a free-text taStatementAboutAmendment paragraph that summarizes the substantive change motivating the OFA filing (for example, the addition or removal of a specific ticker from the Fair Access scope, with an effective date). This narrative is the most concise indicator of the amendment's subject and is typically the only field that materially differs from the operator's previous ATS-N submission.

<partOne> — Identifying Information

Identifying information about the ATS and its broker-dealer operator: the broker-dealer registration flag, the ATS legal name, any marketed names under atsNames, the BD SEC file number, the BD CRD number, the primary self-regulatory organization (typically FINRA), the effective FINRA membership date, the MPID, the public website, and a structured primary-business-address (street, city, state, ZIP).

<partTwo> — Activities of the Broker-Dealer Operator and Affiliates

A series of yes/no radio responses (rb*) paired with free-text expansions (ta*) covering whether the BD operator or its affiliates may enter or route orders into the ATS, whether subscribers may opt out of interacting with such orders, arrangements with other trading centers, products and services offered to subscribers (such as market-data distribution), employee access to confidential trading information (CTI), engagement of service providers (data-center, matching-engine, and clearing providers are commonly named), and the procedures used to safeguard CTI.

<partThree> — Manner of Operations

The largest part of the form, restating Items 1 through 26 of Form ATS-N. Typical fields cover: subscriber types and eligibility or exclusion conditions; hours of operation; means of order entry and connectivity (FIX/SBE protocol versions, co-location facilities); supported order types and matching rules (price/time priority and similar); minimum and maximum order sizes; opening, reopening, and suspension procedures; fee schedule (per-share rebates and charges, market-data fees expressed as dollar ranges); trade-reporting facility used; clearance and settlement arrangements; market-data sourcing; Fair Access status under Rule 301(b)(5); and aggregate platform statistics.

Items 24 and 25 of Part III are the substantive locus of every ATS-N/OFA filing. Item 24 covers Order Display and Execution Access and Item 25 covers Fair Access compliance; the amendment exists specifically to update one of these items within the seven-day disclosure window. Updates frequently take the form of adding or removing specific NMS stock symbols from the Fair Access scope, accompanied by an effective date.

<partFour> — Contact and signature

Contact information for the person responsible for the filing (name, title, telephone, email) and the signature and certification fields completing the form.

xslATS-N_X01/primary_doc.xml — the rendered view

This file is an XHTML 1.0 Strict document produced by EDGAR's ATS-N_X01 XSL stylesheet from the same primary_doc.xml. It begins with a <!DOCTYPE html> declaration, references /css/ATSN_print.css, and presents the form as a printable filer form: a cover sheet, an "ATS-N/OFA: Filer Information" header, a table of contents anchored to each section (#partI, #partIIitem1, ..., #partIV), and a human-readable rendition of every item using radio-button images (radio-checked.jpg, radio-unchecked.jpg) and <div class="fakeBox"> field stylings. It is informationally redundant with the raw XML — every value displayed in the rendering originates from the structured XML — but it is the artifact a human reviewer would see on EDGAR.

Exhibits

Form ATS-N/OFA permits, and frequently includes, exhibits attached to the submission. The most common is a redline document showing the amended language against the prior text, enumerated in documentFormatFiles under the canonical EDGAR type label ATS-N EX-3 REDLINE. Exhibit file names are chosen by the filer (for example BOATS_EX3_FA_3.31.2025.pdf) and the dataset preserves these names. Exhibit content is narrative legal prose and tabulation of the amended items; it complements but does not replace the structured XML, which remains the authoritative machine-readable representation of the disclosure.

Included content

Each record contains:

• the normalized metadata.json summary;
• the raw primary_doc.xml submission with full <headerData> and <formData> trees;
• the EDGAR XSL-rendered XHTML view at xslATS-N_X01/primary_doc.xml;
• all filer-supplied exhibit documents in their original (typically PDF) form.

The documentFormatFiles array in metadata.json enumerates every document in the original EDGAR submission, including the URL of the complete-submission text file.

Excluded or separate content

Image files included in the original EDGAR submission (logos, scanned signatures, embedded graphics referenced by the filer) are excluded from the dataset. The complete-submission SGML .txt envelope is referenced by URL in metadata.json (linkToTxt) but is not redistributed inside the record folder; the record holds the decomposed component documents instead. There is no XBRL instance, no financial-report data, and no series-and-classes information for this form type, and the corresponding metadata fields are present but empty.

Interpretation and extraction notes

Full restatement vs. diff. Although the OFA amendment is regulatorily scoped to changes in Part III Items 24 and 25, the XML schema requires the full form body, so every record contains a complete restatement of Parts I through IV. Downstream extractors comparing successive ATS-N filings for the same operator will see most fields unchanged across an OFA filing, with the diff concentrated in Items 24 or 25 and reflected in plain language in the cover-sheet taStatementAboutAmendment. Any apparent change outside Items 24 and 25 in an OFA filing is unusual and may reflect a transcription difference rather than a substantive amendment.

Element-name typing. The element-name prefixes in formData (tx, ta, rb, cb) are stable across filers and across time and can be used as reliable type indicators for automated extraction. The duplication of parent radio answers as attributes on conditional wrapper elements means a flat XPath query on a leaf element can resolve its conditional context without traversing back up the tree.

Cover narrative parsing. The cover-page taStatementAboutAmendment is free text. Identifying the precise Item (24 vs. 25) and the affected NMS stock symbol(s) generally requires light natural-language parsing of that field, cross-validated against changes detected in the structured Item 24/25 elements between successive filings.

Cross-record joins. Identifiers useful for joining records across filings include the operator's cik, the ATS fileNumber (013-NNNNN), the BD SEC file number, the CRD number, and the MPID — all of which are present in <partOne> and, for cik and fileNo, also in metadata.json's entities array. Because the universe of NMS Stock ATSs is small, repeat filers dominate; the same operator identifiers recur across records and the substantive variation lies in the taStatementAboutAmendment, the values of Item 24/25 fields, and the dated effective triggers cited in the cover narrative.

Authoritative copy. The XSL-rendered XHTML file is informationally redundant with the raw XML and is intended for human display rather than as a separate data source; downstream pipelines should treat primary_doc.xml as the authoritative copy.

Exhibit presence variability. Filings vary in the presence and number of exhibit PDFs: some OFA records contain only the XML and the rendered HTML, while others attach a redline exhibit covering the affected text.

Who Files or Publishes This Dataset, and When

Who files

Form ATS-N/OFA is filed by the registered broker-dealer that operates an NMS Stock ATS. The filer is always:

• a broker-dealer registered with the SEC under Section 15 of the Exchange Act,
• a member of an SRO (in practice, FINRA), and
• the operator of an alternative trading system, as defined in Rule 300 of Regulation ATS, that trades NMS stocks (exchange-listed equities subject to Regulation NMS).

The ATS itself is not a separate registrant. EDGAR identifies the filer by the broker-dealer operating entity's CIK and ATS file number (e.g., 013-XXXXX), not by the trading-venue brand name. The population is small and well-defined: the operators of U.S. NMS Stock ATSs already on Form ATS-N. This includes equities dark pools, ECN-style venues, and conditional-indication-of-interest venues.

Out of scope:

• Non-NMS-stock ATSs (fixed income, government securities, etc.) — they file Form ATS confidentially under Rule 301(b)(2) and never file ATS-N/OFA.
• National securities exchanges — they amend rules via Form 19b-4.
• Internalizers, single-dealer platforms, and foreign venues that do not meet the ATS definition or are not SEC-registered broker-dealers.
• Issuers of the NMS stocks named in a filing — they are subjects of the affected-symbol list, not reporting persons.

What triggers a record

The filing is event-driven, not periodic. An NMS Stock ATS must file Form ATS-N/OFA whenever information previously disclosed in Part III, Item 24 (Rule 304 order display and execution access) or Item 25 (Rule 301(b)(5) fair access) of its Form ATS-N becomes inaccurate or incomplete.

Typical triggers:

• Crossing a Rule 301(b)(3) display/access threshold in additional NMS stocks, or falling below it in stocks previously covered.
• Crossing or dropping below a Rule 301(b)(5) fair access threshold in one or more NMS stocks (the Blue Ocean ATS sample, for instance, removes ticker CHAU from Fair Access scope).
• Operational changes to how the ATS implements display, execution access, or fair access standards previously described in Items 24 or 25.

Changes to any other part of Form ATS-N (ownership, fees, order types, hours, subscriber procedures, etc.) are filed as different Rule 304(a)(2) amendment subtypes — not as ATS-N/OFA. ATS-N/OFA is reserved exclusively for Items 24 and 25.

When the record is due and when it becomes public

Rule 304(a)(2)(i)(D) sets a fixed deadline: no later than seven calendar days after the Item 24 or Item 25 information becomes inaccurate or incomplete. The clock runs from the underlying change in fact (e.g., the threshold-crossing date or effective date of the operational change), not from internal review or board approval.

ATS-N/OFA filings are public on EDGAR upon submission. Unlike initial Form ATS-N filings and material amendments under Rule 304(a)(2)(i)(A)-(C), they are not subject to a Commission declaration or effectiveness review, so each accession enters the public record on its filing date. If Items 24 or 25 information changes again later, the operator files a new ATS-N/OFA. Each amendment stands as a complete Items 24/25 update as of its filing date.

Important distinctions

• ATS-N/OFA vs. initial Form ATS-N and material amendments: initial filings and Rule 304(a)(2)(i)(A)-(C) material amendments go through a Commission review window before becoming operative; ATS-N/OFA does not.
• Form ATS-N vs. Form ATS: only NMS Stock ATSs file the public Form ATS-N regime. Non-NMS-stock ATSs file the confidential Form ATS and never produce ATS-N/OFA records.
• Filer vs. ATS brand: EDGAR records the broker-dealer operator as the filer. The trading-venue trade name appears in the txNMSStockATSName cover field, not as an independent registrant.
• No paper or pre-EDGAR history: Form ATS-N is electronic-only and post-dates the 2018 Regulation ATS-N adoption; ATS-N/OFA traffic on EDGAR begins after the 2019 transition, with this dataset's coverage starting August 2022.

How This Dataset Differs From Similar Datasets or Filings

Form ATS-N/OFA sits inside a tightly bounded family of Alternative Trading System disclosures under Regulation ATS. The most useful comparison targets are the other ATS-N amendment types, the legacy Form ATS regime for non-NMS ATSs, and the Rule 19b-4 channel that exchanges use for analogous order-display and fair-access changes.

Form ATS-N (initial filing)

The foundational Rule 304 disclosure for NMS Stock ATSs. It contains the full structured disclosure set, including Part III Items 24 (order display and execution access) and 25 (fair access). ATS-N/OFA is a narrow amendment that updates only Items 24 and 25 when those disclosures become inaccurate or incomplete. Form ATS-N is also gated on a Commission effectiveness review before becoming public; ATS-N/OFA is public on filing and due within seven calendar days of the triggering inaccuracy.

Form ATS-N/UA (material updates)

The material-update amendment for everything outside Items 24 and 25 (subscriber types, order types, fees, affiliates, conflicts). Form ATS-N/UA is forward-looking and filed at least 30 days before implementation, subject to Commission review. ATS-N/OFA is reactive, post-event, scope-limited to display and access, and operates on a seven-day notice clock.

Form ATS-N/MA (material amendments)

Captures material amendments that take effect upon Commission declaration of effectiveness. The defining contrast with ATS-N/OFA is the timing model: Form ATS-N/MA is gated on Commission action, while ATS-N/OFA is a notice obligation under Rule 304(a)(2)(i)(D) and becomes public immediately on filing.

Form ATS-N/CA (correcting amendments)

Used to correct inaccuracies or omissions in prior ATS-N filings that do not amount to material change. The trigger is informational correction of a past document. Form ATS-N/CA, by contrast, reflects that the underlying operational facts about display or fair access have changed. Typo-level fixes belong in ATS-N/CA; substantive shifts in volume-threshold compliance, fair-access posture, or order-display obligations belong in ATS-N/OFA.

Form ATS (legacy / non-NMS ATSs)

The Rule 301(b)(2) filing used by ATSs trading non-NMS securities (corporate debt, munis, non-NMS equity). It is filed confidentially and generally not made public, the opposite of the ATS-N regime. There is no Form ATS analog to ATS-N/OFA because Items 24 and 25 are specific to NMS Stock ATSs. The two regimes cover disjoint venue populations and are not substitutable.

Rule 19b-4 SRO rule filings (exchange parallel)

National securities exchanges use the Section 19(b) / Rule 19b-4 process to amend rules on order display, access, and execution priority. The subject matter parallels ATS-N/OFA Items 24 and 25, but the procedural model differs sharply: 19b-4 filings undergo public notice-and-comment and run on operative-on-filing or approval-required tracks. For cross-venue market-microstructure work, 19b-4 covers the exchange side and ATS-N/OFA covers the ATS side; neither substitutes for the other.

Key differences at a glance

• Scope: ATS-N/OFA is restricted to Items 24 and 25; every other ATS-N amendment covers a broader or different disclosure surface.
• Timing: Seven calendar days after the disclosure becomes inaccurate, versus 30 days pre-implementation (UA), Commission effectiveness (MA), or no fixed operational trigger (CA).
• Publication: Public on filing, with no Commission gating, unlike ATS-N (effectiveness review) and Form ATS (non-public).
• Trigger: Driven by operational facts, especially crossing the Rule 301(b)(5) volume thresholds that activate fair-access obligations, rather than by discretionary feature, fee, or affiliate changes.
• Filer population: NMS Stock ATSs only, and only those whose display or access posture has materially shifted.

ATS-N/OFA is the post-event, narrow-scope, public-on-filing amendment within the ATS-N family, isolated to order-display and fair-access disclosures. It complements but does not replace Form ATS-N (full baseline), ATS-N/UA and ATS-N/MA (broader material changes with pre-implementation or effectiveness gating), ATS-N/CA (non-material corrections), or Form ATS (non-NMS, non-public). A user tracking when an NMS Stock ATS has shifted its fair-access posture or order-display architecture within a tight reporting cycle will find that signal uniquely in ATS-N/OFA.

Who Uses This Dataset

The Form ATS-N/OFA Files Dataset draws a narrow, technical audience working in equity market structure, broker-dealer compliance, and ATS regulation. Each user group maps to specific record elements rather than the filing as a whole: Item 24 and Item 25 amendment text, identified NMS stocks, volume threshold values, fair-access representations, exhibit redlines, and the seven-day filing cadence.

Sell-side market structure analysts

Analysts at broker-dealers and execution consultancies track threshold crossings to maintain venue scorecards. They pull the affected NMS stock list, the specific threshold breached, the trigger date, and the operator's narrative on how display or access obligations will be met, feeding periodic market structure notes and client briefings on which dark pools have entered a fair-access regime for given symbols.

Buy-side execution and algo R&D teams

Execution desks and smart-order-router developers at asset managers, hedge funds, and prop trading firms read Item 24 and Item 25 amendment text to recalibrate venue rankings, dark-pool toxicity scores, and routing tables. Updated subscriber-category, order-type, and access-criteria language drives decisions on whether a venue is included or suppressed in a given algorithmic strategy on specific symbols.

Broker-dealer best-execution and compliance committees

Compliance officers and best-execution committees at firms that operate or route to ATSs read peer Rule 301(b)(5) representations, fair-access policy text, written grant-and-deny standards, and any change in volume measurement methodology. Outputs include committee minutes, supplementary Rule 605/606 analysis, and venue-approval memos. Firms that themselves operate an NMS stock ATS use peer filings as a benchmark for drafting their own seven-day amendments.

ATS securities counsel

Outside securities lawyers and in-house disclosure counsel use the corpus as a precedent library when drafting amendments under Rule 304(a)(2)(i)(D). They mine peer filings for trigger-event phrasing, level of symbol-list granularity, framing of operator responses, and redlined exhibit structure to support filing checklists and comment-letter responses.

Regulator examination and surveillance staff

Examination staff and market-surveillance analysts at federal securities regulators and the broker-dealer SRO treat the dataset as a longitudinal record of each ATS's display and fair-access posture. They check timeliness against the seven-day rule, consistency between Form ATS-N base filings and OFA amendments, completeness of Item 24/25 updates, and repeated threshold crossings on the same symbols, feeding examination scoping, sweep planning, and enforcement referrals.

Exchange and ATS competitive-intelligence teams

Strategy teams at registered exchanges and competing ATSs monitor affected-symbol lists, operator-response descriptions, and exhibit redlines to map how rival venues are tightening or loosening access tiers and display behavior. Outputs feed product roadmaps and sales pitches to liquidity providers.

Academic market-microstructure researchers

Finance and economics researchers use OFA filings as event data for studies on dark-pool transparency and fair-access enforcement. Filing dates, affected-symbol lists, and Item 24/25 narrative text are merged with consolidated trade-and-quote and academic price datasets to build event panels for working papers and journal articles.

Market-data vendors and venue-reference engineering teams

Data engineers at vendors building venue-reference and execution-quality products parse XML metadata, PDF exhibits, and JSON sidecars to extract venue identifiers, amendment effective dates, threshold values, and affected-symbol lists. The output populates venue master files, change-log feeds, and analyst dashboards.

LLM and RAG developers for execution and compliance tooling

Teams building retrieval-augmented systems for venue-specific Q&A index Item 24/25 passages and redline exhibits so users can ask what changed in a venue's fair-access policy and get a citation back to the precise amendment.

Market structure journalists

Reporters covering dark pools and alternative venues use threshold-crossing disclosures to identify when a specific ATS has tipped into fair-access territory on a high-profile NMS stock. They focus on the affected-symbol disclosure, the operator's narrative response, and the amendment timing.

Specific Use Cases

Concrete workflows the Form ATS-N/OFA Files Dataset supports:

• Detecting fair-access threshold crossings by symbol. Parse the cover-sheet taStatementAboutAmendment together with Part III Item 25 fields across successive filings for each operator (joined on cik and ATS fileNumber) to extract the NMS stock symbols newly entering or leaving the Rule 301(b)(5) fair-access regime, with the cited effective date. Output feeds a venue-by-symbol fair-access status table used by smart-order-router configuration and venue scorecards.

• Recalibrating dark-pool routing tables. Diff Item 24 (Order Display and Execution Access) language between an operator's prior ATS-N filing and the new OFA amendment to flag changes in display posture, subscriber eligibility tiers, or execution-access criteria for specific symbols. Buy-side execution teams use the diff to suppress or re-include a venue in an algo strategy on the affected symbols within the seven-day notice window.

• Building an ATS-N/OFA precedent library for counsel. Index the taStatementAboutAmendment narratives and ATS-N EX-3 REDLINE exhibits across all filers, keyed to the triggering item (24 vs. 25) and trigger event (threshold crossing, symbol addition, methodology change). Counsel drafting a new seven-day amendment retrieves comparable trigger phrasings, symbol-list granularity, and redline structures as templates.

• Monitoring compliance with the seven-day filing clock. Compute the gap between the effective date cited in taStatementAboutAmendment and the EDGAR filedAt timestamp in metadata.json for every record, grouped by operator. Surveillance staff use the resulting timeliness panel to scope examinations, identify repeat late filers, and target operators with recurring threshold crossings on the same symbols.

• Populating venue-reference master files. Extract structured fields from <partOne> (ATS legal name, marketed atsNames, MPID, BD CRD number, FINRA membership date, primary website, business address) plus the entities block in metadata.json to refresh the venue master record on each amendment. Vendors emit change-log entries tied to accession numbers for downstream execution-quality and reference-data products.

• Event studies on fair-access transitions. Use filedAt, the cited effective date, and the affected-symbol list as the event timestamp and treatment set, joined with TAQ or academic trade datasets, to measure pre/post effects on spreads, fill rates, and dark-volume share. The structured Item 24/25 fields disambiguate display-side from access-side events in the panel.

• Competitive-intelligence tracking of rival ATS access tiers. Track each competitor's access-tier and display-architecture changes by extracting the radio-button (rb*) answers and accompanying ta* expansions in Items 24 and 25, and correlating with the redline exhibit. Strategy teams update positioning maps showing which venues are tightening versus loosening subscriber access on which symbol cohorts.

Dataset Access

Dataset Index JSON API: https://api.sec-api.io/datasets/form-atsn-ofa-files.json This endpoint returns dataset metadata, including the dataset name, description, last updated timestamp, earliest sample date, total record count and total size, the form types covered (ATS-N/OFA), the container format (ZIP), and the included file types (XML, PDF, JSON). It also provides the download URL for the full dataset archive and the list of individual container files, each with its size, record count, last updated timestamp, and download URL. This endpoint can be polled daily to detect which containers were updated in the most recent refresh run, allowing selective downloads of only the changed containers. This endpoint does not require an API key.

Example response:

          1
          {
        

          2
            "datasetId": "1f13365b-9ae0-6a51-ba9c-3a1bd377585a",
        

          3
            "datasetDownloadUrl": "https://api.sec-api.io/datasets/form-atsn-ofa-files.zip",
        

          4
            "name": "Form ATS-N/OFA Files Dataset",
        

          5
            "updatedAt": "2026-04-16T08:44:55.531Z",
        

          6
            "earliestSampleDate": "2022-08-01",
        

          7
            "totalRecords": 117,
        

          8
            "totalSize": 8709568,
        

          9
            "formTypes": ["ATS-N/OFA"],
        

          10
            "containerFormat": "ZIP",
        

          11
            "fileTypes": ["XML", "PDF", "JSON"],
        

          12
            "containers": [
        

          13
              {
        

          14
                "downloadUrl": "https://api.sec-api.io/datasets/form-atsn-ofa-files/2026/2026-03.zip",
        

          15
                "key": "2026/2026-03.zip",
        

          16
                "size": 412883,
        

          17
                "records": 4,
        

          18
                "updatedAt": "2026-04-16T08:44:55.531Z"
        

          19
              }
        

          20
            ]
        

          21
          }
        

Download Entire Dataset: https://api.sec-api.io/datasets/form-atsn-ofa-files.zip?token=YOUR_API_KEY Downloads the complete dataset, covering all Form ATS-N/OFA filings from August 2022 to present, as a single ZIP archive. This endpoint requires an API key.

Download Single Container: https://api.sec-api.io/datasets/form-atsn-ofa-files/2026/2026-03.zip?token=YOUR_API_KEY Downloads one monthly container ZIP instead of the entire dataset, which is useful for incremental updates or fetching a specific time range. This endpoint requires an API key.

Frequently Asked Questions

What form does this dataset cover?

The dataset covers Form ATS-N/OFA, the Order Display and Fair Access Amendment to Form ATS-N, filed by NMS Stock Alternative Trading Systems under Rule 304(a)(2)(i)(D) of Regulation ATS. It is the narrowest of the ATS-N amendment variants and is reserved for updates to Part III, Items 24 (Order Display and Execution Access under Rule 301(b)(3)) and 25 (Fair Access under Rule 301(b)(5)) of an operator's effective Form ATS-N.

What does one record in this dataset represent?

One record is a single EDGAR submission of Form ATS-N/OFA, identified by its 18-digit accession number and materialized as a folder under a YYYY-MM filing-month partition. The folder bundles the canonical primary_doc.xml submission, an EDGAR-rendered XHTML view at xslATS-N_X01/primary_doc.xml, any filer-supplied PDF exhibits (most commonly an ATS-N EX-3 REDLINE), and a normalized metadata.json summary.

Who is required to file Form ATS-N/OFA?

The filer is always a registered broker-dealer that operates an NMS Stock ATS, registered with the SEC under Section 15 of the Exchange Act and a member of an SRO (in practice, FINRA). The trading venue itself is not a separate registrant; EDGAR identifies the filer by the broker-dealer operator's CIK and ATS file number formatted as 013-NNNNN.

What triggers an ATS-N/OFA filing and what is the deadline?

The filing is event-driven. An NMS Stock ATS must file ATS-N/OFA whenever previously disclosed information in Item 24 or Item 25 of its Form ATS-N becomes inaccurate or incomplete — typically because the venue has crossed or fallen below a Rule 301(b)(3) display/access threshold or a Rule 301(b)(5) fair-access threshold on one or more NMS stocks. Rule 304(a)(2)(i)(D) sets a fixed deadline of no later than seven calendar days after the underlying change in fact, and the filing is public on EDGAR upon submission with no Commission effectiveness review.

How does this dataset differ from Form ATS-N initial filings or other ATS-N amendments?

Form ATS-N is the full baseline disclosure and is gated on a Commission effectiveness review; ATS-N/UA covers material updates outside Items 24 and 25 and must be filed at least 30 days before implementation; ATS-N/MA takes effect on Commission declaration; and ATS-N/CA captures non-material corrections. ATS-N/OFA is uniquely the post-event, narrow-scope, public-on-filing amendment isolated to order-display and fair-access disclosures, with a seven-day notice clock and no Commission gating.

What file format is the dataset distributed in?

The dataset is distributed as monthly ZIP containers partitioned by filing month under a YYYY-MM/<accession-no-dashes>/... folder structure. The file types inside each record are XML (the canonical primary_doc.xml and the XSL-rendered XHTML companion), PDF (filer-supplied exhibits, most commonly redlines), and JSON (the normalized metadata.json summary). There is no XBRL, no SGML, and no pre-XML legacy format for this form type.

What time period does the dataset cover?

The dataset covers Form ATS-N/OFA filings from August 1, 2022 onward. This window sits fully within the structured EDGAR ATS-N XML era, so format consistency is high across every record: each filing conforms to the same ATS-N XML schema and is rendered by the same EDGAR ATS-N_X01 XSL stylesheet.