Form ATS-N/MA Files Dataset

The Form ATS-N/MA Files Dataset is a per-filing collection of every Form ATS-N/MA submission accepted by EDGAR — the material-amendment variant of Form ATS-N, mandated by Rule 304 of Regulation ATS for alternative trading systems that trade NMS stocks. Each record represents one complete EDGAR submission of a material amendment by a single registered broker-dealer that operates an NMS Stock ATS, identified by accession number and packaged with all source documents the operator submitted (image files excluded) plus a normalized metadata summary. Filings are bundled into monthly ZIP containers, with coverage starting September 2019 — the operative date of the Form ATS-N regime — and continuing to the present. The dataset preserves both the structured XML payload (cover page, Part I identification, Part II broker-dealer/affiliate activities, Part III Manner of Operations, Part IV signatures) and the operator-supplied PDF exhibits (Schedule A, Schedule B, and the Exhibit 3 redline that pinpoints the changed language relative to the prior effective Form ATS-N).

Dataset APIs

Dataset Files

What This Dataset Contains

The dataset captures every Form ATS-N/MA filing made under Rule 304(a)(2)(i)(A) of Regulation ATS, which requires NMS Stock ATS operators to file material amendments to a previously effective Form ATS-N at least 30 calendar days before implementing the change. Coverage begins in September 2019, the early operational period of the Form ATS-N regime, and runs through the present. Each filing is delta-oriented: the operator restates the affected sections of Form ATS-N with the new language and attaches a redline so the Commission and the public can see exactly what changed against the prior effective form.

Records are delivered as per-filing folders inside monthly ZIP containers (YYYY-MM.zip). Each filing folder is named using the digits-only accession number (for example 000001961720000368/) under a dated top-level prefix YYYY-MM/ inside the archive. The file types found in the dataset are XML (raw submission and cover-page documents and their XHTML renderings), PDF (the exhibit attachments), and JSON (the per-filing metadata summary). Image files referenced by the original EDGAR submission are excluded; everything else from the submission is preserved.

Content Structure of a Single Record

A single record in the Form ATS-N/MA Files Dataset is one complete EDGAR submission of Form ATS-N/MA. The unit of a record is the entire filing as accepted by EDGAR, identified by its accession number and packaged as a per-filing folder that holds every source document the broker-dealer operator submitted (image files excluded) plus a normalized metadata summary. A record corresponds to a single material-amendment event reported by a single NMS Stock ATS operator, not to an individual disclosure paragraph or a single exhibit. Multiple amendments by the same ATS appear as separate records, each with its own accession number and its own folder.

What the underlying filing is

Form ATS-N/MA is the material-amendment variant of Form ATS-N, the disclosure form mandated by Rule 304 of Regulation ATS for alternative trading systems that trade NMS stocks. The form is a structured EDGAR submission that mirrors the printed Form ATS-N section ordering: a cover page; Part I identifying information for the broker-dealer operator and the ATS; Part II structured disclosures about broker-dealer and affiliate activities on the ATS (Items 1-7); Part III "Manner of Operations" disclosures (Items 1-26, covering subscribers, order types, matching methodology, fees and rebates, segmentation, routing, suspension of trading, and related operational specifics); and Part IV signatures and contact information. The submission must be filed at least 30 calendar days before the operator implements the change. ATS-N/MA filings are inherently delta-oriented: the filer restates the affected sections of Form ATS-N with the new language and attaches a redline so the Commission and the public can see exactly what changed against the prior effective form.

Components of a per-filing folder

Each per-filing folder contains the following components:

• metadata.json — normalized filing-summary JSON.
• primary_doc.xml — the raw machine-readable ATS-N/MA submission XML.
• xslATS-N_X01/primary_doc.xml — the XHTML rendering of primary_doc.xml produced by applying the SEC stylesheet ATS-N_X01.
• coverpage.xml — the raw machine-readable cover-page XML.
• xslATSN_COVER_X01/coverpage.xml — the XHTML rendering of coverpage.xml produced by applying the SEC stylesheet ATSN_COVER_X01.
• Zero or more PDF exhibits attached by the filer (Schedule A, Schedule B, the Exhibit 3 redline, and any additional schedules or supporting documents the operator chose to attach).

Exhibit PDF file names are filer-chosen and not standardized (ScheduleA.pdf, SchB.pdf, Exhibit3.pdf, and other variants may all coexist), so the authoritative mapping from a PDF to its formal exhibit role is the type code carried by the corresponding entry in metadata.json, not the on-disk file name.

metadata.json

metadata.json is the canonical summary of the filing. Its top-level keys describe the filing envelope and the document inventory:

• formType — always the string "ATS-N/MA" for records in this dataset.
• accessionNo — the hyphenated EDGAR accession number (for example 0000019617-20-000368).
• filedAt — the ISO-8601 timestamp, with timezone, of EDGAR acceptance.
• description — the human-readable filing description, typically of the form "Form ATS-N/MA - Material Amendment to Form ATS-N (Rule 304(a)(2)(i)(A)): [Amend]".
• linkToFilingDetails — URL to the styled HTML rendering on sec.gov.
• linkToTxt — URL to the SGML "Complete submission text file".
• linkToHtml — URL to the EDGAR filing index page.
• linkToXbrl — empty for this form type.
• documentFormatFiles — an array enumerating every document in the EDGAR submission. Each entry carries a sequence number, byte size, documentUrl pointing to the EDGAR-hosted file, an exhibit type code, and an optional description. The type codes that appear include ATS-N/MA (the primary submission), COVER PAGE, ATS-N EX-1 SCHD A BD (Schedule A identifying the broker-dealer operator), ATS-N EX-2 SCHD B BD (Schedule B), and ATS-N EX-3 REDLINE (the redlined comparison of operational changes). Several documents have a paired "Screen Reader Accessible File" entry that points at the raw XML or PDF version of the same content.
• entities — an array of the parties on the filing. Each entry holds cik, companyName (with a role suffix such as "(Filer)"), fileNo, irsNo, stateOfIncorporation, fiscalYearEnd, act, type, and filmNo.
• seriesAndClassesContractsInformation — empty for ATS-N/MA filings (this form has no fund series/class structure).
• dataFiles — empty for ATS-N/MA filings.
• id — an opaque internal identifier.

primary_doc.xml

primary_doc.xml is the structured, machine-readable submission. It declares the namespace http://www.sec.gov/edgar/atsn for ATS-N-specific elements and uses http://www.sec.gov/edgar/common and http://www.sec.gov/edgar/atsncommon for shared types. The root <edgarSubmission> is partitioned into two subtrees:

• <headerData> — the submission envelope. It contains submissionType (the literal ATS-N/MA), accessionNumber, and <filerInfo> with the filer CIK, the CCC placeholder, the SEC fileNumber, and submission flags (liveTestFlag, overrideInternetFlag, confirmingCopyFlag).
• <formData> — the disclosure payload, organized into sections that mirror the printed Form ATS-N:
  • <cover> — the NMS Stock ATS name (txNMSStockATSName) and the free-text taStatementAboutAmendment, the operator's narrative description of what is being amended.
  • <partOne> — identifying information for the broker-dealer operator and the ATS. Fields include the broker-dealer flag, the ATS legal name (txPart1Item2ATSName), one or more alternate names under <atsNames><atsName .../></atsNames>, the SEC file number, the CRD number, the registered NSA name and the effective membership date, the NMS Stock MPID, the ATS website URL, the primary site address, and flags governing the publication of certain exhibits.
  • <partTwo> — the structured Part II responses about broker-dealer and affiliate activities on the ATS (Items 1-7), where each item appears as a yes/no checkbox or radio response paired with a free-text explanation. For example, rbPart2Item1aArePermittedToEnterInterest is the radio-button response and taPart2Item1aUnitNamesEnterInterest is the matching textarea explanation.
  • <partThree> — the "Manner of Operations" responses (Items 1-26), covering subscriber types, eligibility, hours of operation, order types and order interaction, matching methodology, fees and rebates, segmentation, routing, suspension of trading, and related operational specifics. Most amendments concentrate their substantive changes in this section.
  • <partFour> — signature and contact information.

Field-name conventions inside <formData> are stable: the prefixes tx (text input), ta (textarea), cb (checkbox), and rb (radio button) precede a partNItemN-style key that aligns directly with the Part-and-Item numbering of the printed form. This convention makes the XML straightforward to map to specific Form ATS-N items for cross-amendment comparison.

coverpage.xml

coverpage.xml lives in the dedicated http://www.sec.gov/edgar/atsn/cover namespace and has a much smaller payload than the primary document. Its root <cov:edgarSubmission> repeats a slim subset of the submission identity and cover-page-printable fields: submissionType, accessionNumber, the filer credentials (filerCik, filerCcc), fileNumber, the ATS name, the taStatementAboutAmendment narrative, the liveTestFlag, the rbOperatesPursuantToFormATS flag, and the same overrideInternetFlag and confirmingCopyFlag markers as the primary document. Functionally, this is the data that EDGAR uses to render the printed cover page of the form.

Rendered XHTML siblings

xslATS-N_X01/primary_doc.xml and xslATSN_COVER_X01/coverpage.xml are full standalone XHTML documents produced by applying the SEC's published XSL stylesheets ATS-N_X01 and ATSN_COVER_X01, respectively, to the corresponding raw XML. They reference SEC-hosted CSS (such as /css/ATSN_print.css) and image assets, and they carry the same disclosure data as the raw XML augmented with form chrome — the OMB approval block, the contents table, and rendered "checked"/"unchecked" radio and checkbox images. They are intended for human display and are functionally redundant with the raw XML for machine extraction.

Exhibit PDFs

The PDF attachments are the operator-provided exhibits to the amendment. Their formal role is identified by the type code of the corresponding entry in documentFormatFiles:

• ATS-N EX-1 SCHD A BD — Schedule A, identifying the broker-dealer operator (its principals, control persons, and related information).
• ATS-N EX-2 SCHD B BD — Schedule B, supplemental broker-dealer identifying information.
• ATS-N EX-3 REDLINE — the redlined comparison showing exactly what changed in the operational disclosure relative to the prior effective Form ATS-N. This exhibit is typically the most informative artifact for understanding the substance of the material amendment, because it pinpoints the changed language at the clause level.

Filers may also attach additional schedules or supporting documents; their formal role is likewise read from the type code in metadata.json, since on-disk file names are filer-chosen and not standardized.

Included content

A record includes the full machine-readable Form ATS-N/MA submission (primary_doc.xml and coverpage.xml), the EDGAR-rendered XHTML versions of those XML documents (under xslATS-N_X01/ and xslATSN_COVER_X01/), every PDF exhibit attached by the filer (Schedule A, Schedule B, redline, and any additional schedules), and a normalized metadata.json filing summary that enumerates each document with its type code and links back to the EDGAR-hosted source. The structured XML preserves every Part-and-Item response the filer entered, including all checkbox/radio-button states and all free-text narrative answers, so the dataset captures both the structured disclosure topology and the qualitative explanation text of the amendment.

Excluded or separate content

Image files referenced by the original EDGAR submission are excluded from the per-filing folder. The previously effective Form ATS-N to which the amendment relates is not bundled with the ATS-N/MA record; it is a separate filing under its own accession number on EDGAR. The SGML "Complete submission text file" wrapper is not stored in the folder, but the URL to it is recorded in metadata.json under linkToTxt. The CSS and image assets referenced by the rendered XHTML are not bundled either; the XHTML files reference them by absolute URL on sec.gov.

Notes on disclosure structure and evolution

Form ATS-N/MA was created by the Regulation ATS amendments that took effect in 2019, when the SEC introduced Form ATS-N to replace the Form ATS regime for ATSs that trade NMS stocks. Dataset coverage starts in September 2019, the early operational period of the Form ATS-N regime. The Part-and-Item structure of the form (cover page; Part I identification; Part II broker-dealer/affiliate activities Items 1-7; Part III Manner of Operations Items 1-26; Part IV signatures) and the underlying XML schema with the tx/ta/cb/rb field-prefix convention have remained stable across the dataset's coverage window. The exhibit vocabulary (ATS-N EX-1 SCHD A BD, ATS-N EX-2 SCHD B BD, ATS-N EX-3 REDLINE) likewise has stayed stable, reflecting a consistent EDGAR document-type taxonomy for this form.

Notes on data format

Form ATS-N/MA has been a structured-XML EDGAR submission since its inception; there is no ASCII-text or plain-HTML era to account for. Each record carries both the raw XML (for machine consumption) and the EDGAR XSL-rendered XHTML (for human display) of the primary document and the cover page. Exhibits have consistently been PDF attachments.

Interpretation notes

• The substantive change introduced by the amendment is best located by combining the taStatementAboutAmendment narrative in <cover> (which states what is being amended) with the redline PDF (ATS-N EX-3 REDLINE), which shows the exact textual delta against the prior Form ATS-N.
• Because the form is structured, every Part-and-Item response in <partTwo> and <partThree> is independently addressable via its element name, and the partNItemN naming convention makes it straightforward to align a given amendment's response to the same item across other ATS-N or ATS-N/MA filings by the same operator.
• The raw XML and the rendered XHTML carry the same disclosure content; downstream extraction should prefer the raw XML for machine processing and treat the XHTML as a presentational mirror.
• metadata.json is the authoritative inventory of the submission: the documentFormatFiles[].type code, not the on-disk file name, identifies the role of each PDF exhibit, since filers pick their own file names.
• The entities array distinguishes parties by their role suffix appended to companyName (for example "(Filer)"); the broker-dealer operator's CIK in entities is the join key to other EDGAR filings by the same operator.
• A material-amendment record does not restate the entire Form ATS-N — it carries the amended sections and the redline. Reconstruction of the full state of an ATS's disclosure at a given point in time requires walking back to the most recent prior Form ATS-N (or initial Form ATS-N) and applying subsequent amendments in sequence.
• The cover-page XML duplicates a slim subset of the primary-document fields (submission identity, ATS name, amendment statement, operating-pursuant-to-Form-ATS flag); when only those fields are needed, the cover-page XML is a lighter parse target than the full primary document.

Who Files or Publishes This Dataset, and When

Each record is a single Form ATS-N/MA submission filed by a registered broker-dealer that operates an alternative trading system trading NMS stocks ("NMS Stock ATS"). The legal filer is always the broker-dealer operator; the ATS itself is a business line of that broker-dealer, not a separate registrant. Affiliates whose ATS-related activities are described in the form are subjects of disclosure, not filers.

The filer population is narrow:

• Registered broker-dealers (Section 15 of the Exchange Act),
• Operating an ATS within the meaning of Rule 300(a) of Regulation ATS, and
• Trading NMS stocks as defined in Rule 600(b) of Regulation NMS — i.e., exchange-listed equities and ETFs.

In practice this covers equity dark pools, institutional crossing networks, block-trading venues, and continuous off-exchange equity matching pools.

When the record is created

Form ATS-N/MA is event-driven, not periodic. A filing exists only when the broker-dealer operator proposes to implement a material change to:

• the operations of the NMS Stock ATS, or
• the ATS-related activities of the broker-dealer operator and its affiliates,

as previously described in the effective Form ATS-N on file.

Typical triggers include changes to order types, matching and order-interaction logic, subscriber segmentation, routing, fees and rebates, market data usage, conflicts-of-interest controls, safeguards for confidential subscriber information, and the affiliated broker-dealer's interaction with the ATS.

Timing rule

Under Rule 304(a)(2)(i)(A), the operator must file the material amendment at least 30 calendar days before implementing the change, and may not implement during that window. After filing:

• The Commission has up to 30 calendar days to declare the amendment effective or to institute proceedings to declare it ineffective.
• If proceedings are instituted, the review period may extend up to an additional 90 days (with a further 60-day extension in specified circumstances), during which the change cannot be implemented.
• If declared ineffective, the change cannot be implemented.
• If the Commission takes no action within the applicable window, the amendment becomes effective by operation of the rule.

Regulatory framework

Form ATS-N and its amendment variants exist under Rule 304 of Regulation ATS, adopted by Release No. 34-83663 (July 2018) and operative from 2019. Rule 304 layers a public disclosure regime for NMS Stock ATSs on top of the broker-dealer/ATS framework of Rule 301. Form ATS-N filings are publicly posted on EDGAR, unlike the legacy non-public Form ATS used by non-NMS ATSs.

The Form ATS-N family includes:

• Form ATS-N — initial operation report; the Commission must declare it effective before the ATS may operate.
• Form ATS-N/MA — material amendment, filed at least 30 calendar days before implementation. (This dataset.)
• Form ATS-N/UA — updating amendment for non-material changes or corrections; filed on a quarterly cycle or promptly, with no pre-implementation waiting period.
• Form ATS-N/OFA — order-form amendment used in Commission-directed contexts.
• Form ATS-N/CA — cessation amendment, filed when the ATS stops operating as an NMS Stock ATS.

Only the /MA variant is included in this dataset.

Important distinctions

Filer versus subjects of disclosure. Affiliates, subscribers, and counterparties referenced in the form are described parties, not filers.

No pre-EDGAR history. Form ATS-N is EDGAR-native. The earliest /MA records appear from September 2019, reflecting the Rule 304 transition for legacy NMS Stock ATSs that converted to the Form ATS-N regime, with material amendments following as those venues evolved.

Amendment chains. Each NMS Stock ATS typically has one effective Form ATS-N supplemented over time by multiple /UA and /MA filings. The /MA records here are incremental change disclosures layered on an underlying initial Form ATS-N, not standalone descriptions of a venue's full operation.

How This Dataset Differs From Similar Datasets or Filings

Form ATS-N/MA sits inside a tightly defined family of disclosures governing alternative trading systems. The most relevant comparisons are the other variants in the ATS-N family, the legacy Form ATS regime for non-NMS Stock ATSs, the quarterly Form ATS-R, and Form 19b-4 for SRO rule changes. Each addresses a different question about the same underlying venues.

Form ATS-N (initial filing)

The initial Form ATS-N is the foundational disclosure an NMS Stock ATS files before commencing operations (or that legacy venues filed during the 2018-2019 transition). It is the full operational portrait: broker-dealer operator, affiliates, subscriber types, order types, matching methodology, fees, market data sources, and conflicts of interest.

ATS-N/MA is a delta against that baseline, describing a single material change. Reconstructing the current state of an ATS requires the initial Form ATS-N as the baseline plus the chronological sequence of MA overlays.

Form ATS-N/UA (updating amendment)

ATS-N/UA covers non-material updates that keep the disclosure current without crossing the materiality threshold: corrections to non-substantive text, contact or officer changes, refinements that do not alter trading-relevant operations. Timing differs sharply: MA filings carry a mandatory 30-day pre-implementation window; UA filings are made promptly after the change with no waiting period.

Form ATS-N/CA (correcting amendment)

ATS-N/CA filings correct inaccurate or incomplete information in a previously filed Form ATS-N, ATS-N/MA, or ATS-N/UA. The trigger is error correction, not operational change. CA filings are reactive and remediation-oriented; MA filings are forward-looking and tied to a planned effective date.

Form ATS-N/OFA (order to file an amendment)

ATS-N/OFA submissions are SEC-initiated, compelled amendments issued when the Commission determines existing disclosure is materially deficient. The defining distinction from ATS-N/MA is causation: MA is operator-initiated and discretionary; OFA is regulator-initiated and enforcement-adjacent.

Form ATS (legacy Reg ATS form for non-NMS Stock ATSs)

Form ATS is the older Regulation ATS notice filing that still applies to ATSs trading non-NMS securities, including fixed-income, corporate bond, and treasury venues. It is filed confidentially under Rule 301(b)(2), whereas Form ATS-N is publicly disseminated. The populations are mutually exclusive: ATS-N/MA covers only NMS Stock ATSs (primarily equity dark pools), while Form ATS covers non-equity venues. Disclosure depth also diverges, with Form ATS being a comparatively short notice and Form ATS-N a detailed public transparency document.

Form ATS-R (quarterly transaction volume report)

Form ATS-R is the quarterly volume report filed by all ATSs (both NMS and non-NMS Stock), containing tabular share counts, dollar volumes, and transaction counts by security type. ATS-R answers "how much trading happened" on a recurring schedule; ATS-N/MA answers "what changed about how the venue operates" on an event-driven basis. The two are complementary, not substitutable.

Form 19b-4 (exchange rule changes)

Form 19b-4 is the closest functional analogue to ATS-N/MA: both are advance-notice filings about operational changes at a trading venue. The differences are substantial:

• Filer population: 19b-4 covers SROs (NYSE, Nasdaq, Cboe, FINRA, options exchanges, clearing agencies); ATS-N/MA covers broker-dealer-operated ATSs.
• Process: 19b-4 triggers a formal notice-and-comment rule-change process with Commission approval orders; ATS-N/MA uses a 30-day prior-notice mechanism without an approval architecture.
• Disclosure style: 19b-4 reads as legal rule text with statutory justification; ATS-N/MA reads as operational narrative answering specific Form ATS-N items.

Together they cover the universe of equity-trading-venue rule changes, but they are not interchangeable.

Boundary summary

The Form ATS-N/MA Files Dataset captures one specific slice: operator-initiated, material, forward-looking amendments to NMS Stock ATS operations, filed publicly with a mandatory 30-day pre-implementation window. It is not the place to find:

• the baseline operational portrait of an ATS (initial Form ATS-N)
• routine non-material updates (ATS-N/UA)
• error corrections (ATS-N/CA)
• SEC-compelled amendments (ATS-N/OFA)
• non-equity ATS structure (Form ATS)
• trading volumes (Form ATS-R)
• exchange rule changes (Form 19b-4)

Its analytical value lies in that narrowness: every record represents a deliberate material change to a U.S. equity ATS, disclosed for public review before it takes effect.

Who Uses This Dataset

Because each amendment describes concrete changes to order types, matching logic, subscriber access, fees, and broker-dealer operator activities, the dataset is consumed by a narrow set of professionals who track venue mechanics and use the 30-day pre-effective window.

Buy-Side Execution and Venue Analysis Teams

Head traders and venue analysts at asset managers, pension plans, and hedge funds maintain internal venue profiles. They read the amendment narrative for changes to order types, segmentation, matching priority, subscriber access, and fee tiers, then update broker wheels, minimum-quantity defaults, and opt-in/opt-out instructions before the effective date.

ATS Operator Compliance and Product Managers

Compliance officers, regulatory counsel, and ATS product managers at competing broker-dealer operators benchmark each other's amendments. They focus on materiality framing, redlined Part III responses, conflict-of-interest disclosures (Part II), and affiliate activity descriptions to calibrate their own filings and pre-filing dialogue with staff.

Market-Structure Researchers

Analysts at brokerages, trading technology vendors, and independent research shops map how the dark pool landscape evolves: new conditional order types, mid-point variants, size-discovery mechanisms, segmentation, and fee structures. Effective dates and operational change descriptions feed published notes, venue taxonomies, and client briefings on off-exchange liquidity.

Regulators and Examiners

Examination staff and rule-enforcement reviewers compare stated operations against observed behavior, prior filings, and peer venues. They focus on consistency across successive amendments, completeness of conflict and affiliate disclosures, surveillance and information-leakage controls, and fee revisions to scope exams and draft deficiency letters.

Policy and Regulatory Affairs Analysts

Policy researchers at industry associations, think tanks, and regulatory affairs groups study the cumulative effect of Rule 304 since 2019. They aggregate amendment frequency, change types, and operator affiliations to support comment letters on market-structure proposals and white papers on dark pool transparency.

Microstructure Academics

Academic researchers use ATS-N/MA filings as ground-truth documentation of venue mechanics during empirical samples. Matching methodology, order-type taxonomies, segmentation rules, and effective dates align with TAQ data for event studies on amendment dates, regime-aware execution-quality models, and agent-based simulations.

TCA Vendors

Transaction cost analytics providers maintain venue dictionaries that drive attribution models. They track changes to mid-point logic, peg references, minimum-quantity rules, conditional routing, IOC behavior, and fees so pre-trade cost models and post-trade attribution reflect the rules in force on each trade date.

Smart Order Router and Algo Engineers

Quant developers and execution-engineering teams update routing tables and order-type mappings against the filings. They focus on technical specifics of order types, time-in-force interactions, anti-gaming controls, opt-outs, and minimum acceptable quantity behavior, aligning SOR releases and regression tests with venue go-live dates.

Competing Venue and Fintech Product Teams

Product managers at execution venues, ATS aspirants, and liquidity-platform fintechs study competitive positioning — fee innovations, new subscriber categories, novel matching variants, and conflict-mitigation controls — to inform roadmap decisions and pitch materials.

Litigation Support and Expert Witnesses

Securities litigators, expert witnesses, and forensic consultants involved in best-execution, dark pool conduct, or disclosure-adequacy disputes use the filings as primary evidence of what a venue represented at a given time. Exact amendment wording, effective dates, affiliate disclosures, and changes to surveillance and information-handling sections support expert reports, depositions, and chronologies aligning representations with trading activity.

Specific Use Cases

The Form ATS-N/MA Files Dataset supports a small set of operational workflows that depend on knowing exactly what an NMS Stock ATS is changing, when the change takes effect, and how the venue's mechanics are now described.

Pre-effective venue reconfiguration on the buy side

Execution desks parse taStatementAboutAmendment and the ATS-N EX-3 REDLINE exhibit on each new filing to identify changes to order types, segmentation tiers, minimum-quantity logic, or matching priority. The 30-day pre-implementation window is used to update broker wheels, opt-out instructions, and minimum acceptable quantity defaults before the effective date so routing aligns with the new venue rules on day one.

TCA venue-dictionary maintenance keyed to effective dates

TCA vendors map each amendment's Part III responses (fees and rebates, mid-point logic, peg references, IOC behavior, conditional order behavior) into versioned venue dictionaries. The amendment's effective date becomes the cutover point in pre-trade cost models and post-trade attribution, so trades printed before and after the change are scored against the disclosure that was in force on the trade date.

Smart-order-router regression and go-live alignment

SOR and algo engineering teams pull the structured Part III fields (partThree order-type, time-in-force, anti-gaming, and opt-out elements) and the redline to update routing tables and per-venue order-type mappings. Regression suites and canary releases are scheduled against the filing's effective date so SOR behavior changes in lockstep with the ATS.

Cross-operator benchmarking of amendment language

ATS compliance teams and regulatory counsel at competing broker-dealer operators compare Part II affiliate-activity disclosures and Part III operational language across peer filings, using the stable partNItemN field naming to align the same item across operators. The comparison feeds materiality framing, conflict-of-interest wording, and pre-filing dialogue with SEC staff on the team's own next amendment.

Longitudinal mapping of dark pool mechanics

Market-structure researchers and microstructure academics walk the chronological sequence of ATS-N/MA records per operator (joined by the filer CIK in entities) on top of the initial Form ATS-N baseline to reconstruct the state of each venue at any past date. The reconstructed timeline is joined to TAQ for event studies on amendment effective dates and for regime-aware execution-quality models.

Litigation chronologies of venue representations

Expert witnesses and forensic consultants in best-execution and dark pool conduct disputes use the per-filing folder as primary evidence of what a venue represented at a specific time. The filedAt timestamp, the cover-page amendment statement, the Part II/III responses, and the redline establish the exact wording and effective date relevant to trades within a contested window.

Regulatory and policy aggregation across the Rule 304 era

Policy analysts and examiners aggregate the corpus by operator, item touched, and change type to study how Rule 304 disclosures have evolved since September 2019. Amendment frequency, recurring Part III items, and clusters of conflict or surveillance-control revisions support comment letters, exam scoping, and white papers on off-exchange transparency.

Dataset Access

Dataset Index JSON API: https://api.sec-api.io/datasets/form-atsn-ma-files.json

This endpoint returns the dataset index as JSON, including dataset metadata (name, description, last updated timestamp, earliest sample date, total records and total size, covered form types, container format, and file types), the download URL for the full dataset archive, and the list of individual container files with per-container size, record count, updated timestamp, and download URL. Poll this endpoint to monitor which containers were modified in the most recent refresh and decide which files to download incrementally. No API key is required to access this endpoint.

Example response:

          1
          {
        

          2
            "datasetId": "1f13365b-9ae0-6a62-9e79-c01e889582ef",
        

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

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

          5
            "updatedAt": "2026-04-16T08:49:30.191Z",
        

          6
            "earliestSampleDate": "2019-09-01",
        

          7
            "totalRecords": 121,
        

          8
            "totalSize": 12473613,
        

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

          10
            "containerFormat": "ZIP",
        

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

          12
            "containers": [
        

          13
              {
        

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

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

          16
                "size": 482113,
        

          17
                "records": 3,
        

          18
                "updatedAt": "2026-04-16T08:49:30.191Z"
        

          19
              }
        

          20
            ]
        

          21
          }
        

Download Entire Dataset: https://api.sec-api.io/datasets/form-atsn-ma-files.zip?token=YOUR_API_KEY

Downloads the full dataset as a single ZIP archive containing all Form ATS-N/MA filings from September 2019 to present. This endpoint requires an API key.

Download Single Container: https://api.sec-api.io/datasets/form-atsn-ma-files/2026/2026-03.zip?token=YOUR_API_KEY

Downloads one individual monthly container ZIP file instead of the entire archive, which is useful for incremental updates or targeted retrieval. Replace the year and month path segments with the container key returned by the dataset index API. This endpoint requires an API key.

Frequently Asked Questions

What form does this dataset cover?

The dataset covers Form ATS-N/MA, the material-amendment variant of Form ATS-N. Form ATS-N/MA is required under Rule 304(a)(2)(i)(A) of Regulation ATS for alternative trading systems that trade NMS stocks, and is filed at least 30 calendar days before the operator implements a material change to its operations.

What does one record in this dataset represent?

One record is a single complete EDGAR submission of Form ATS-N/MA by a single NMS Stock ATS operator, identified by accession number. Each record is delivered as a per-filing folder containing metadata.json, the raw primary_doc.xml and coverpage.xml, their EDGAR XSL-rendered XHTML siblings, and any PDF exhibits the operator attached (Schedule A, Schedule B, the Exhibit 3 redline, and any additional schedules).

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

Only registered broker-dealers that operate an NMS Stock ATS — equity dark pools, institutional crossing networks, block-trading venues, and continuous off-exchange equity matching pools — file Form ATS-N/MA. The legal filer is always the broker-dealer operator; affiliates, subscribers, and counterparties referenced in the form are subjects of disclosure rather than filers.

When does an operator file Form ATS-N/MA?

The form is event-driven, not periodic. A filing is triggered when the operator proposes a material change to the operations of the NMS Stock ATS or to the ATS-related activities of the broker-dealer operator and its affiliates — for example, changes to order types, matching logic, subscriber segmentation, fees and rebates, routing, or conflicts-of-interest controls. The amendment must be filed at least 30 calendar days before implementation.

How does Form ATS-N/MA differ from Form ATS-N/UA?

The dividing line is materiality. Form ATS-N/MA is reserved for material changes and carries a mandatory 30-day pre-implementation window during which the change cannot be implemented. Form ATS-N/UA covers non-material updates and corrections, has no pre-implementation waiting period, and follows a quarterly filing cycle.

What time period does the dataset cover?

Coverage starts in September 2019 — the operative period of the Form ATS-N regime adopted under Rule 304 of Regulation ATS — and runs through the present. There is no pre-EDGAR history because Form ATS-N is EDGAR-native and did not exist before the Rule 304 transition.

What file formats are included in each record?

Each record contains XML (the raw primary_doc.xml and coverpage.xml and their XHTML renderings under xslATS-N_X01/ and xslATSN_COVER_X01/), PDF (the operator-supplied exhibits such as Schedule A, Schedule B, and the Exhibit 3 redline), and JSON (the normalized metadata.json filing summary). Image files referenced by the original EDGAR submission are excluded; everything else from the submission is preserved. Records are bundled into monthly ZIP containers named YYYY-MM.zip.