The Form S-4MEF Files Dataset is a per-filing collection of S-4MEF registration statements filed with the SEC's EDGAR system under Rule 462(b) of the Securities Act of 1933. Each record represents a single S-4MEF accession — a short-form companion registration statement that adds up to twenty percent more securities of the same class to an already-effective Form S-4 covering a business combination such as a merger, acquisition, exchange offer, or holding-company reorganization. Filers are the same US operating-company, bank-holding, REIT, or topco issuers (and any guarantor co-registrants) named on the underlying S-4; foreign private issuers, which use the parallel F-4MEF, are not included. Each accession is packaged as a self-contained folder containing a structured metadata.json filing descriptor and the SGML-wrapped .htm documents that constituted the filing. Dataset coverage begins with April 1997 filings, reflecting EDGAR availability after the 1996 adoption of Rule 462(b) and the related "MEF" form family, and continues to present.
Programmatically retrieve the full list of dataset archive files, download URLs and dataset metadata.
Dataset Index JSON API
Download the entire dataset as a single archive file.
Download Entire Dataset:
Download a single container file (e.g. monthly archive) from the dataset.
Download Single Container:
The dataset captures the textual portion of every S-4MEF accession on EDGAR within its coverage window. One record corresponds to one accession, identified by its EDGAR accession number and packaged as a per-filing folder named after the accession with dashes stripped (an 18-digit string such as 000080316425000005). Folders are grouped beneath a YYYY-MM/ directory inside monthly ZIP containers, and the dataset is distributed in ZIP archives carrying TXT, JSON, and HTML file types.
Form S-4MEF is not a stand-alone disclosure document. It is a "more-securities" companion to a previously declared-effective Form S-4 — the registration form used for securities issued in business-combination transactions. Rule 462(b) lets a registrant add up to twenty percent more securities of the same class to a still-effective registration statement, and the S-4MEF becomes effective at the moment EDGAR accepts it. Because the form's legal function is purely to graft additional securities onto an existing registration, its substantive content is intentionally thin: it identifies the prior S-4 file number, declares the additional class and amount of securities, calculates the incremental registration fee, and incorporates by reference the prospectus, financial statements, business descriptions, risk factors, and exhibits of the earlier S-4. The substantive deal disclosure lives in the parent S-4, not in the S-4MEF.
Each record bundles two layers: a structured metadata.json filing descriptor and the textual portion of the original EDGAR submission — the SGML-wrapped .htm documents. Binary GRAPHIC images that were part of the original submission are intentionally excluded from the per-filing folder by dataset policy but remain catalogued in metadata.json so the inventory of original artifacts is preserved.
Inside a per-filing folder, content is organized in two correlated layers. The first is metadata.json, a single JSON object that captures filing-level identifiers, dates, parties, and an inventory of the submitted documents. The second is the raw EDGAR submission payload: a sequence of .htm files, each an SGML <DOCUMENT> envelope around an HTML body. The SGML header tags inside each document file (<TYPE>, <SEQUENCE>, <FILENAME>, <DESCRIPTION>) carry the same identifiers as the matching documentFormatFiles entry in metadata.json, so the JSON inventory and the on-disk file set are in 1:1 correspondence — with the documented exceptions of omitted graphics and the omitted concatenated submission .txt. Document order follows the EDGAR <SEQUENCE> numbering: sequence 1 is the primary S-4MEF cover document, followed by the legal opinion, auditor consents, and fee-calculation exhibits, with any graphic entries and the complete-submission text file as the trailing inventory rows.
metadata.json — filing-level descriptormetadata.json is one JSON object per accession. Its fields are:
formType — EDGAR form code, fixed as "S-4MEF".accessionNo — canonical dashed EDGAR accession (for example "0000803164-25-000005"); the un-dashed form is the folder name.filedAt — full ISO 8601 filed timestamp with timezone offset, recording the moment EDGAR accepted the submission.effectivenessDate — the date the additional registration becomes effective. For S-4MEF this typically coincides with the filed date, since Rule 462(b) makes the additional registration effective on filing.description — human-readable form description, normally "Form S-4MEF - Registration adding securities to prior Form S-4 registration [Rule 462(b)]".linkToFilingDetails — URL of the primary document on sec.gov/Archives.linkToTxt — URL of the EDGAR concatenated submission TXT for the accession.linkToHtml — URL of the EDGAR ...-index.htm filing index page.linkToXbrl — XBRL instance link; an empty string for S-4MEF, which carries no XBRL payload of its own.id — a 32-character hex dataset record identifier.documentFormatFiles — an ordered array of submitted-document descriptors. Each element carries sequence (a string ordinal; the bundled complete-submission text file uses a single-space placeholder), size (byte length as a string), documentUrl (EDGAR URL), description (free-text label supplied by the filer, such as "<REGISTRANT> FORM S-4MEF" or "<REGISTRANT> EXHIBIT 5 TO FORM S-4MEF"), and type (the EDGAR document-type code such as S-4MEF, EX-5, EX-23.x, EX-FILING FEES, GRAPHIC). The final array element, with description: "Complete submission text file", points to the SGML mega-file <accession>.txt.entities — an array of party objects, one per EDGAR header role (filer, co-registrant, guarantor). Each entity carries cik, companyName (suffixed with the role label, e.g. "(Filer)", "(Co-Registrant)"), type (the form code), fileNo (the SEC file number, typically the 333- prefix of the prior S-4 to which the additional securities are being attached), irsNo, stateOfIncorporation (USPS state code), fiscalYearEnd (MMDD), act (Securities Act number, "33" for S-4MEF), sic (SIC code with description, for example "6022 State Commercial Banks"), filmNo, and tickers (array of ticker symbols).seriesAndClassesContractsInformation — array reserved for fund-style series/class contract metadata; empty for S-4MEF, which is used for operating-company business combinations rather than fund offerings.dataFiles — array reserved for ancillary structured data files; empty for S-4MEF.Every .htm document inside the folder is an EDGAR SGML <DOCUMENT> envelope around an HTML body. The header tags (no closing forms) appear at the top, the rendered content sits inside a <TEXT> block wrapping an <HTML> payload, and the document closes with </TEXT></DOCUMENT>:
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<DOCUMENT>
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<TYPE>S-4MEF
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<SEQUENCE>1
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<FILENAME>choices4mef_022125.htm
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<DESCRIPTION>CHOICEONE FORM S-4MEF
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<TEXT>
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<HTML>
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... (full HTML registration statement or exhibit body) ...
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</HTML>
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</TEXT>
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</DOCUMENT>
The values of <TYPE>, <SEQUENCE>, <FILENAME>, and <DESCRIPTION> mirror the corresponding documentFormatFiles entry in metadata.json, allowing direct cross-walking between the JSON inventory and the on-disk files in either direction.
S-4MEF filings are intentionally minimal, and the documents found in a record reflect that:
S-4MEF registration statement (sequence 1). A short cover-style document that re-uses the Form S-4 facing-page template. It identifies the registrant (exact legal name, state of incorporation, SIC code, IRS EIN, principal-executive-office address, telephone number, agent for service), checks the Rule 462(b) box, names the title and amount of additional securities being registered, and explicitly cross-references the earlier effective S-4 by its 333- file number. The document incorporates the entire content of the prior S-4 by reference rather than restating it, and carries the registrant's signatures together with the standard Securities Act statements and the cover-page calendar information.EX-5 — Opinion of Counsel. A legal opinion, typically one or two pages, addressing the legality and valid issuance of the additional securities being registered. It is signed by outside counsel and consents to the opinion's filing as an exhibit.EX-23.x — Consents of Independent Registered Public Accounting Firms. One consent per audit firm whose audit reports are being incorporated from the underlying S-4, numbered EX-23.1, EX-23.2, EX-23.3, etc. depending on how many auditors are involved across the registrant and any target. Each consent authorizes the inclusion or incorporation by reference of the auditor's report on financial statements that already appeared in the earlier S-4.EX-FILING FEES (Exhibit 107). The Calculation of Filing Fee Table required by Rule 411 and the SEC's modernized fee-disclosure rules. It is a structured table listing the newly registered securities, the proposed maximum offering price, the fee rate, the fee paid, and any fee offset, and is the basis on which EDGAR validates the registrant's payment for the additional twenty percent.GRAPHIC entries. Image files (signature graphics, firm logos, scanned figures) referenced from metadata.json but excluded from the per-filing folder. Their documentFormatFiles entries remain so the inventory faithfully reflects the original EDGAR submission.<accession>.txt is the trailing entry in documentFormatFiles and is reachable through linkToTxt, but it is not redistributed inside the per-filing folder because the constituent .htm documents already cover its textual content.Other exhibits occasionally appear depending on the transaction — additional auditor consents, an updated tax opinion, a powers-of-attorney exhibit, or supplementary signatures — but the cover S-4MEF together with the EX-5 / EX-23.x / EX-FILING FEES triplet is the canonical content set.
Each record includes the full structured filing descriptor (metadata.json), the primary S-4MEF cover document, every textual or HTML exhibit actually filed with the S-4MEF (legal opinion, auditor consents, filing-fee table, and any other narrative or schedule exhibits), and the SGML <DOCUMENT> headers that wrap each document file. All filer, co-registrant, identifier, fee-related, and document-inventory information needed to interpret the filing without round-tripping to EDGAR is present in metadata.json.
Two categories of content are omitted from the per-filing folder. First, binary image files of any GRAPHIC document type are excluded by dataset policy; their existence and original filenames remain listed in metadata.json. Second, the EDGAR concatenated <accession>.txt submission file is not duplicated inside the folder — its textual content is already covered by the union of the individual .htm documents — and a URL for it is preserved in linkToTxt and in the trailing documentFormatFiles row. Substantive disclosures that the S-4MEF incorporates by reference from the earlier S-4 (prospectus, business descriptions, financial statements, risk factors, pro forma data, and the bulk of the exhibit list) are not part of an S-4MEF record itself; they live in the parent S-4 accession, locatable via the fileNo (333-XXXXXX) value carried in the entities block.
S-4MEF has been stable in its narrow Rule 462(b) function since the rule's adoption in 1996, and dataset coverage begins with April 1997 filings. The internal anatomy described above — short cover registration statement, legal opinion, auditor consents, fee table, and incorporation by reference of the earlier S-4 — has been the canonical pattern throughout. The most material content evolution affects the filing-fee disclosure: under amendments to Rule 411 and the related fee-disclosure rules effective in early 2022, the fee calculation moved from the cover-page fee table into a dedicated structured Exhibit 107 (EX-FILING FEES). S-4MEF filings made after that transition therefore carry the fee table as a separate document with type: "EX-FILING FEES", while older filings present the fee calculation on the face of the registration statement itself.
Submission formatting also evolved. Late-1990s filings were predominantly plain ASCII inside the SGML <DOCUMENT> envelope, sometimes with embedded uuencoded graphics. Through the early 2000s filers shifted to HTML inside the same SGML envelope, and modern S-4MEF filings are submitted as HTML (.htm) documents wrapped in that envelope. The dataset preserves the envelope verbatim — <TYPE>, <SEQUENCE>, <FILENAME>, and <DESCRIPTION>, and the <TEXT>...<HTML> body remain visible at the top and bottom of each .htm file.
Several nuances matter when working with S-4MEF records:
fileNo value in entities (typically 333-XXXXXX) is the linkage to the parent S-4 accession that carries the prospectus, financial statements, and substantive deal disclosure.entities array can contain multiple objects when a filing has co-registrants or guarantors, with each object's companyName suffixed by its EDGAR role label (e.g. "(Filer)", "(Co-Registrant)"). The role suffix is part of the string and must be stripped if a clean issuer name is required.effectivenessDate is a calendar date (the regulatory effective date) while filedAt is a full timestamp with timezone offset. They generally agree by virtue of Rule 462(b)'s automatic effectiveness, but the two fields should be read explicitly rather than assumed equal.documentFormatFiles is the authoritative inventory of what was originally submitted. GRAPHIC rows are listed even though the corresponding image files are not in the folder, and the trailing complete-submission text file is listed even though it is not redistributed. Consumers enumerating redistributed files should filter on type != "GRAPHIC" and exclude the "Complete submission text file" row.<DOCUMENT> header is part of every .htm payload. HTML parsers that assume a clean <!DOCTYPE>/<html> root will pick up stray <TYPE>, <SEQUENCE>, <FILENAME>, and <DESCRIPTION> tags unless the SGML preamble is stripped before parsing.linkToXbrl is empty and dataFiles is unpopulated.The registrant on a Form S-4MEF is the same issuer (and the same co-registrants) named on the underlying effective Form S-4. The filer is the entity issuing the additional securities used as merger consideration, not the target, the target's shareholders, the exchange agent, or the financial advisors.
Typical filers include:
Foreign private issuers do not appear in this dataset; their analogous top-up filing is Form F-4MEF, paired with an effective F-4. Issuers using S-1, S-3, or S-11 for the underlying registration use S-1MEF, S-3MEF, or S-11MEF respectively.
The S-4MEF is event-driven, not periodic. It is filed when, before the closing of the business combination, the issuer determines that the share count or aggregate offering amount registered on the prior effective S-4 will be insufficient to deliver the consideration required to close. Common operational triggers:
Rule 462(b) permits the additional registration only if it does not exceed 20 percent of the maximum aggregate offering price registered on the prior S-4 and the prior S-4 remains effective at the time of filing.
Filings cluster in the days, hours, or even minutes before the deal closing, once the final deliverable share count is known. Effectiveness is automatic on filing under Rule 462(b): no staff acceleration order, no waiting period, no further review. The required registration fee on the additional securities is paid with the filing under Section 6(b).
Substantive disclosure is not repeated. The S-4MEF incorporates by reference the underlying S-4, the joint proxy statement/prospectus, financial statements, and exhibits. The filing itself contains only the cover page, the prior S-4 file number, the additional amount and class of securities, the fee calculation, signatures, and limited exhibits (typically a legality opinion and an auditor consent).
The dataset begins in April 1997, reflecting EDGAR availability following the 1996 adoption of Rule 462(b) and the related "MEF" form family. There is no meaningful paper-era history for this form.
Form S-4MEF occupies a narrow slot in the Securities Act registration system: it is a Rule 462(b) "Money / Maximum Effort Filing" that adds up to 20 percent more securities to an already-effective Form S-4 covering a business combination. Because the form is procedurally narrow and substantively thin, the most useful comparisons are to (1) the parent S-4 family it depends on, (2) the other Rule 462(b) MEF variants that share its mechanics on different base forms, and (3) adjacent M&A disclosure filings that researchers sometimes confuse with registration filings.
Form S-4 is the full registration statement for securities issued in business combinations: mergers, exchange offers, holding-company reorganizations, and similar acquisition structures. It carries the joint proxy/prospectus, target and acquirer financials, pro formas, fairness opinions, deal background, and risk factors.
S-4MEF is parasitic on a specific effective S-4. It repeats none of that content. It identifies the prior S-4 by file or accession number, registers up to 20 percent more securities of the same class, pays the incremental fee, and incorporates the earlier filing by reference. S-4 accessions are orders of magnitude larger; S-4MEF accessions are short procedural records. Anyone studying merger disclosure substance must work from the S-4 itself; the S-4MEF only signals that the registrant needed additional headroom.
Both S-4/A and S-4MEF reference a base S-4, but the resemblance ends there. S-4/A amendments carry full disclosure content and can rewrite portions of the prospectus to address staff comments, refresh financials, or revise deal terms. They are not effective on filing — pre-effective amendments need SEC declaration of effectiveness, and post-effective amendments use a separate effectiveness mechanism. S-4MEF, by contrast, is effective on filing under Rule 462(b), capped at a 20 percent uplift, and never amends disclosure. S-4/A is the substantive amendment trail; S-4MEF is a registration-capacity adjustment.
F-4MEF is the cross-border analogue: a Rule 462(b) MEF tied to an effective Form F-4, the business-combination registration statement for foreign private issuers. Mechanics are identical (20 percent cap, immediate effectiveness, incorporation by reference). The differences are filer population and the underlying disclosure regime — F-4 follows FPI accommodations (e.g., IFRS financials, different executive-compensation thresholds), and F-4MEF inherits that base. For a complete merger-registration view, S-4MEF and F-4MEF should be analyzed in parallel, split by issuer status.
All MEF variants share the same skeleton — short filing, 20 percent cap, immediate effectiveness, incorporation by reference — but differ in the base offering they extend:
S-4MEF is uniquely tied to business-combination registrations, so its filings cluster around merger pricings and exchange-ratio adjustments rather than IPO or shelf-takedown windows. A combined dataset of all 462(b) MEFs would mix offering types with very different economic and disclosure contexts; the S-4MEF Files Dataset isolates the M&A subset.
Form 425 covers written communications about pending business combinations under Rule 425, Rule 165, and Rule 14a-12 — press releases, investor presentations, employee Q&A, transcripts. It registers nothing and sits outside the effectiveness chain. S-4MEF and 425 often appear in the same deal docket but answer different questions: 425 captures what the parties said publicly during the offer period; S-4MEF captures that the registrant needed more registration capacity.
For stock-for-stock mergers, the S-4 and the merger proxy are typically combined into a single joint proxy/prospectus, so PREM14A and DEFM14A overlap heavily with S-4 in content. They are not registration statements and have no Rule 462(b) analogue. Use DEFM14A for disclosure substance; use the S-4 family — and S-4MEF for any 462(b) top-ups — for registration mechanics.
424B prospectuses are sometimes confused with 462(b) MEFs because both are short, mechanical post-effectiveness filings. The distinction is clean: a 424B discloses final pricing and offering terms but registers no additional securities; a 462(b) MEF registers more securities and raises the registration ceiling. In S-4 deals, Rule 424 filings are uncommon because the S-4 prospectus is part of the registration statement, so this confusion is more frequent in S-1/S-3 contexts.
The Form S-4MEF Files Dataset is defined by the intersection of three constraints: (1) filings governed specifically by Rule 462(b), so each record is short, immediately effective, and capped at a 20 percent uplift; (2) a base form that must be Form S-4, so every record relates to a business-combination registration rather than an IPO, shelf, or REIT offering; and (3) substantive disclosure that lives elsewhere — in the parent S-4 and any S-4/A — leaving each S-4MEF accession as a thin procedural record (cover-page identifiers, additional securities and class, incremental fee, incorporation-by-reference statement).
The dataset is most useful when joined to the parent S-4 family, identifying which mergers required more registered shares than originally anticipated (often because the exchange ratio, market price, or deal sizing shifted between effectiveness and closing). It does not substitute for the underlying merger disclosure, M&A communications (425), proxy materials (DEFM14A / PREM14A), or the broader MEF universe across other base forms — and none of those capture the specific 462(b) capacity-expansion event in business-combination registrations that S-4MEF uniquely records.
Form S-4MEF sits at the intersection of M&A execution, securities registration, and fee calculation. The dataset is used by a defined set of transactional and analytical professionals working with a small, recurring set of fields: registrant CIK, parent S-4 file number, incremental share count and class, registration fee, and filing timestamp.
Transactional counsel use the dataset as a precedent library when drafting an S-4MEF on a live deal. They pull comparable filings to model the fee table, the incorporation-by-reference paragraph, signature blocks, and descriptions of the additional shares. The same records support Rule 462(b) eligibility checks: same-day filing relative to parent effectiveness, the 20 percent cap, and correct fee inclusion.
Deal teams treat S-4MEF filings as late-stage capacity-adjustment signals in pending stock-for-stock transactions. Incremental share count and filing date indicate that exchange-ratio drift, stock-price movement, or rounding pushed merger consideration above the original registration and that closing is near. Bankers use this to refine timing estimates and benchmark how often comparable transactions required a top-up.
In-house securities-administration, treasury, and corporate finance teams reference how peers sized the original S-4 reservation, when an MEF top-up was required, and how the incremental fee was computed. The parent-file linkage, additional share count, and fee fields feed share-reserve buffer modeling, closing-checklist fee budgeting, and coordination with transfer agents on post-effective share availability.
Risk-arb desks watch S-4MEF filings as a near-closing indicator, since the form is typically filed days before completion. Analysts match the parent S-4 file number against pending-deal trackers, attribute incremental capacity to price or ratio movement, and update closing-probability and timing assumptions in position-level models.
Engineering teams at commercial deal databases ingest the dataset to enrich transaction records with registration-history metadata. They extract registrant CIK, parent file number, additional shares, fee paid, and timestamp, then derive deal-level attributes such as final registered share count, cumulative S-4 plus S-4MEF fees, and capacity-adjustment event counts. The dataset's compact volume relative to other registration-form datasets makes complete historical backfill practical.
Researchers studying M&A execution and SEC registration practice use the dataset as a clean sample of late-stage capacity adjustments. Typical analyses include the distribution of incremental percentages relative to the 20 percent cap, the relationship between deal size and MEF probability, and the time gap between S-4 effectiveness and the subsequent MEF, all driven by the registrant CIK, parent file number, share count, fee, and date fields.
Disclosure-control officers at registrants and staff at filing-agent service providers audit historical Rule 462(b) usage to confirm that fee calculations, parent-file references, and incorporation-by-reference language match internal records and current practice. Fee-calculation software vendors validate their calculators against historical filings, particularly across fiscal years where the SEC fee rate changed, using the additional shares, proposed maximum aggregate offering price, fee rate, and fee paid.
The Form S-4MEF Files Dataset supports a small set of well-defined workflows around late-stage Rule 462(b) capacity additions to merger registrations. Each use case below leans on specific record fields rather than the dataset as a whole.
Transactional counsel pull historical filings to model a current S-4MEF. The primary S-4MEF document (sequence 1) supplies the cover-page template, signature block, and incorporation-by-reference paragraph; EX-FILING FEES (Exhibit 107) supplies the fee-table format; EX-5 and the EX-23.x consents supply standard exhibit shells. Filtering entities[].sic narrows precedents to comparable industries (for example, 6022 for bank mergers).
Risk-arb and event-driven desks join entities[].fileNo (the parent 333-XXXXXX S-4 file number) to a pending-deal tracker, then read filedAt as a closing-imminence flag — S-4MEFs are typically filed days before completion. The incremental share amount on the EX-FILING FEES table quantifies how much exchange-ratio drift or share-price movement pushed consideration above the original S-4 reservation, feeding closing-probability and timing models.
M&A data vendors ingest each record's accessionNo, entities[].cik, parent fileNo, filedAt, and the share count and fee paid from EX-FILING FEES, then derive deal-level attributes: final registered share count (parent S-4 plus MEF top-ups), cumulative registration fees, and a binary "required 462(b) top-up" flag per transaction. The compact historical record set makes a full backfill straightforward.
Fee-calculation vendors and filing-agent compliance teams replay the EX-FILING FEES table — proposed maximum aggregate offering price, fee rate, fee offset, fee paid — against their calculators, especially across fiscal-year boundaries where the SEC fee rate changed. The dataset spans pre-2022 cover-page fee tables and post-2022 standalone Exhibit 107 filings, providing test fixtures for both formats.
Academic and strategy researchers compute the ratio of MEF-registered shares to parent-S-4-registered shares using entities[].fileNo as the join key to the parent registration. Aggregate distributions across the dataset show how close registrants ran to the 20 percent Rule 462(b) cap, the gap between S-4 effectiveness and MEF filing (filedAt minus parent effective date), and how MEF probability scales with deal size or industry.
In-house disclosure-control teams reconcile their own historical S-4MEFs in the dataset against internal closing checklists. They verify that entities[].fileNo matches the intended parent S-4, that effectivenessDate aligns with filedAt (Rule 462(b) automatic effectiveness), and that the EX-5 opinion and EX-23.x consents listed in documentFormatFiles match counsel and auditor records — surfacing any prior filings where exhibits, fee math, or parent linkages diverged from policy.
Dataset Index JSON API: https://api.sec-api.io/datasets/form-s4mef-files.json
This endpoint returns dataset metadata including the name, description, last updated timestamp, earliest sample date (1997-04-01), total records and total size, covered form types (S-4MEF), the container format (ZIP), the included file types (TXT, JSON, HTML), the download URL for the full archive, and the list of individual container files with per-container size, record count, updated timestamp, and download URL. Use this endpoint to monitor which containers were updated in the latest refresh and decide which ones to download incrementally. This endpoint does not require an API key.
Example response:
1
{
2
"datasetId": "1f13365b-9ae0-69f5-a064-8484706b69f9",
3
"datasetDownloadUrl": "https://api.sec-api.io/datasets/form-s4mef-files.zip",
4
"name": "Form S-4MEF Files Dataset",
5
"updatedAt": "2026-04-15T18:16:02.926Z",
6
"earliestSampleDate": "1997-04-01",
7
"totalRecords": 949,
8
"totalSize": 3379495,
9
"formTypes": ["S-4MEF"],
10
"containerFormat": "ZIP",
11
"fileTypes": ["TXT", "JSON", "HTML"],
12
"containers": [
13
{
14
"downloadUrl": "https://api.sec-api.io/datasets/form-s4mef-files/2026/2026-03.zip",
15
"key": "2026/2026-03.zip",
16
"size": 13818783,
17
"records": 4,
18
"updatedAt": "2026-04-15T18:16:02.926Z"
19
}
20
]
21
}
Download Entire Dataset: https://api.sec-api.io/datasets/form-s4mef-files.zip?token=YOUR_API_KEY
Downloads the complete dataset as a single ZIP archive containing every S-4MEF filing from April 1997 to present. This endpoint requires an API key.
Download Single Container: https://api.sec-api.io/datasets/form-s4mef-files/2026/2026-03.zip?token=YOUR_API_KEY
Downloads a single monthly container instead of the full dataset, useful for incremental updates after detecting changes via the index JSON API. This endpoint requires an API key.
The dataset covers Form S-4MEF, a short-form companion registration statement filed under Rule 462(b) of the Securities Act of 1933. Each S-4MEF adds up to twenty percent more securities of the same class to an already-effective Form S-4 used for a business combination, and becomes effective at the moment EDGAR accepts it.
One record represents a single S-4MEF accession, packaged as a per-filing folder named after the EDGAR accession number with dashes stripped. The folder contains a structured metadata.json filing descriptor and the SGML-wrapped .htm documents that constituted the filing — typically the primary S-4MEF cover document, an EX-5 legal opinion, one or more EX-23.x auditor consents, and an EX-FILING FEES table.
The filer is the same issuer (and any co-registrants such as guarantor subsidiaries) named on the underlying effective Form S-4 — typically a US public operating company, a topco holding company in a stock-for-stock merger, a bank or insurance holding company, or a REIT issuing equity as merger consideration. Foreign private issuers do not appear in this dataset; their analogous top-up filing is Form F-4MEF.
The S-4MEF is event-driven, not periodic. It is filed in the days, hours, or minutes before deal closing when the issuer determines that the share count or aggregate offering amount on the prior effective S-4 will be insufficient — for example, after a negotiated increase in the exchange ratio, a higher final count of target shares and equity awards, or movement in a floating exchange ratio that pushes the deliverable share count above the originally registered amount.
Form S-4 is the full, staff-reviewed registration statement carrying the joint proxy/prospectus, target and acquirer financials, pro formas, fairness opinions, and risk factors. S-4MEF is parasitic on a specific effective S-4: it repeats none of that content, registers up to 20 percent more securities of the same class, pays the incremental fee, and incorporates the earlier filing by reference. Anyone studying merger disclosure substance must work from the S-4 itself; the S-4MEF only signals that the registrant needed additional registration capacity.
The dataset is distributed as monthly ZIP container archives. Each ZIP contains per-filing folders organized under YYYY-MM/, and each folder holds a metadata.json descriptor plus the original .htm documents (each wrapped in an SGML <DOCUMENT> envelope). The container format is ZIP and the included file types are TXT, JSON, and HTML.
Coverage begins with April 1997 filings, reflecting EDGAR availability following the 1996 adoption of Rule 462(b) and the related "MEF" form family, and continues to the latest refresh of the API. There is no meaningful paper-era history for this form.