The Form S-1MEF Files Dataset is a complete corpus of every Form S-1MEF registration statement filed on EDGAR from February 1996 to the present. One record corresponds to a single S-1MEF submission — a Rule 462(b) "immediately effective" companion registration that adds up to 20% more securities to an already-effective Form S-1 — identified by its 18-digit dashless accession number and packaged as a folder containing a metadata.json manifest plus the original EDGAR submission documents. Filers are domestic operating-company issuers, special purpose acquisition companies (SPACs), and other Form S-1 registrants that need to upsize an offering at pricing without staff review. The dataset preserves the S-1MEF cover page, the legality opinions of counsel (EX-5.x), the auditor and expert consents (EX-23.x), the Inline XBRL filing-fee exhibit (EX-FILING FEES), and any other textual exhibits, each retained inside its EDGAR SGML document wrapper. Records are bundled into monthly ZIP containers under YYYY/YYYY-MM.zip keys, enabling deal-sizing analytics, league-table credit attribution, capital-markets precedent retrieval, and pricing-day event studies across the form's full history.
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The dataset captures every Form S-1MEF submission EDGAR has accepted since the SEC adopted Securities Act Rule 462(b) in 1996. Form S-1MEF is a short, dependent registration statement filed under Rule 462(b) that registers additional securities — capped at 20% of the maximum aggregate offering price of an already-effective Form S-1 — and becomes effective immediately upon filing, without further SEC action. Because of this construction, an S-1MEF does not restate the substantive disclosures of the parent S-1; it incorporates them by reference. The filing body is therefore dominated by registrant identification, the Rule 462(b) check-box election that names the prior S-1 file number, a description and fee calculation for the additional securities, and the signature page. The disclosure-heavy content (business description, risk factors, MD&A, plan of distribution, prospectus narrative, financial statements and notes) lives only in the parent S-1 and is referenced rather than reproduced.
The historical population of S-1MEF filers is concentrated in IPO-stage issuers — particularly blank-check / SPAC vehicles classified under SIC 6770 — that need to upsize an offering on the day of pricing, and in operating-company IPOs that elect to use the 20% overflow capacity at pricing. On disk, each record is a folder named after the filing's 18-digit dashless accession number (for example 000121390025108371) containing a single metadata.json manifest plus the original EDGAR submission documents that made up the filing on filing day: the S-1MEF registration statement and every textual exhibit attached to it. Folders are bundled into monthly ZIP containers (YYYY-MM.zip) under YYYY/ directories. Image binaries referenced by the exhibits (JPG, GIF, PNG) are not bundled, but every other constituent of the original submission is preserved verbatim, including the EDGAR SGML document wrapper that surrounds each HTML file. The accession folder is the canonical record unit; the manifest defines its membership. The dataset is distributed in ZIP container format and includes JSON, HTML, and TXT file types.
Each record is built from two layers. The first is metadata.json, a per-accession header and manifest exposing the filing's structured EDGAR attributes (form type, accession number, effectiveness and filing timestamps, filer entities and identifiers, and a complete file inventory). The second is the set of original EDGAR submission documents, each an HTML file prefixed by the standard EDGAR SGML document wrapper (<DOCUMENT>, <TYPE>, <SEQUENCE>, <FILENAME>, <DESCRIPTION>, <TEXT>) that names the document's exhibit type and sequence. Together these two layers cover the entire textual content of the EDGAR submission: the substantive S-1MEF registration statement, the legality opinions of counsel, the auditor's consent, the Inline XBRL filing-fee exhibit, and any other textual exhibits the registrant attached.
metadata.json manifestmetadata.json carries the structured EDGAR header for the filing. Its top-level fields are:
formType — always "S-1MEF".accessionNo — the 20-character dashed accession number (e.g. 0001213900-25-108371).effectivenessDate — YYYY-MM-DD. By Rule 462(b) construction this typically equals the filing date.filedAt — full ISO-8601 timestamp with offset.description — fixed boilerplate identifying the filing as a Rule 462(b) registration adding securities to a prior Form S-1.linkToFilingDetails — direct EDGAR URL to the primary S-1MEF document.linkToTxt — URL to the SGML-wrapped full-submission text file on EDGAR.linkToHtml — URL to the EDGAR filing-index HTML page.linkToXbrl — empty, because S-1MEF carries no cover-page or financial-statement XBRL; the only XBRL artifact in the filing is the EX-FILING FEES exhibit, which is reachable via documentFormatFiles[] and dataFiles[] rather than this field.id — opaque hex hash serving as the dataset-internal record identifier.Three array fields complete the manifest:
documentFormatFiles[] enumerates every document in the EDGAR submission with sequence, size (bytes), documentUrl, description, and type. Type values found in the dataset are S-1MEF for the registration statement, EX-5.1 and EX-5.2 for opinions of counsel, EX-23.1 (and where applicable EX-23.2, EX-23.3) for auditor or expert consents, EX-FILING FEES for the Inline XBRL fee exhibit, GRAPHIC for image attachments (which are not bundled but remain listed here), and an unnamed sequence-blank catch-all entry pointing to the complete submission text file. The fee-table entry's documentUrl is rendered through EDGAR's Inline XBRL viewer (https://www.sec.gov/ix?doc=...).dataFiles[] enumerates extracted XBRL instance documents that EDGAR derives from the iXBRL exhibit. For S-1MEF the typical entry is a single *_htm.xml instance corresponding to the EX-FILING FEES exhibit; this artifact is referenced in the manifest but is not bundled into the ZIP payload.entities[] lists the filer-side parties. Each entity carries cik, companyName with role suffix (e.g. (Filer)), fileNo (the new 333-prefixed file number assigned to this S-1MEF), irsNo, act ("33" for the Securities Act of 1933), formType, sic (combined numeric SIC code and label, e.g. 6770 Blank Checks), stateOfIncorporation as an EDGAR code (e.g. E9 for the Cayman Islands), fiscalYearEnd as MMDD, filmNo, and a tickers[] list of trading symbols.A seriesAndClassesContractsInformation[] array is structurally present but always empty for S-1MEF, because this form is not used by registered investment companies.
Every non-metadata file is an HTML document prefixed with the EDGAR SGML wrapper:
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<DOCUMENT>
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<TYPE>S-1MEF
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<SEQUENCE>1
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<FILENAME>ea0249505-08.htm
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<DESCRIPTION>REGISTRATION STATEMENT
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<TEXT>
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<HTML>... (full HTML body) ...</HTML>
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</TEXT>
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</DOCUMENT>
The <TYPE> line maps one-to-one to the EDGAR exhibit type and to the matching entry in documentFormatFiles[]; <SEQUENCE> matches the manifest sequence; <FILENAME> matches the on-disk file name. Image references inside exhibits (for example <IMG SRC="ex5-1_001.jpg">) survive in the HTML, but the underlying JPG/GIF/PNG binaries are not bundled. Filenames are not standardized — they follow the filing agent's conventions. Recent filings prepared by EdgarAgents/Novaworks tend to use names like ea0249505-08.htm for the primary document and ea024950508ex5-1_<project>.htm for exhibits; older mid-1990s through 2000s entries use shorter, sometimes accession-derived names. The canonical way to identify a document's role is via the <TYPE> header or documentFormatFiles[].type, never via filename pattern matching.
The primary document reproduces a Form S-1 cover page in HTML. It opens with the standard EDGAR header lines ("As filed with the U.S. Securities and Exchange Commission on …", a placeholder "Registration No. 333-_____", and the form caption "FORM S-1 / REGISTRATION STATEMENT / UNDER / THE SECURITIES ACT OF 1933"), followed by a three-column block giving the registrant's state or jurisdiction of incorporation, primary SIC code, and IRS Employer Identification Number. Below this come the registrant's name and principal-office address, the agent-for-service block, and one or more "copies to" blocks naming legal counsel.
The substantive cover-page element is the Rule 462(b) check-box, which explicitly identifies the file number of the prior effective Form S-1 (e.g. 333-289152); selecting this box is what makes the filing a 462(b) registration. Filer-status check-boxes follow (large accelerated filer, accelerated filer, non-accelerated filer, smaller reporting company, emerging growth company).
The body is short: an explanatory note describing the additional securities being registered and confirming that they do not exceed the 20% Rule 462(b) cap; the calculation-of-registration-fee table, which in modern filings is incorporated by reference to the EX-FILING FEES exhibit rather than restated; and the signature page at part II-2 carrying /s/ signatures for the principal executive officer, the principal financial and accounting officer, and the directors, with corresponding dates. The HTML body is heavily styled with inline CSS produced by EDGAR's HTML conversion pipeline (Times New Roman PS Std fonts, machine-generated _idGen class names from InDesign exports,   non-breaking spaces) — characteristic of EDGAR-rendered exhibits rather than human-authored markup.
Short letterhead-style HTML letters from issuer's counsel opining that the additional securities, when issued and paid for as described in the registration statement, will be validly issued, fully paid, and non-assessable. EX-5.1 is the U.S. or onshore counsel's opinion. When the registrant is incorporated outside the United States — common for SPAC-era S-1MEFs domiciled in the Cayman Islands or the British Virgin Islands — an EX-5.2 from local counsel (firms such as Maples and Calder, Conyers Dill & Pearman, Walkers, or Ogier) is included to address the laws of the place of incorporation. Each opinion opens with letterhead and addressee, a "Re:" line referencing the Registration Statement on Form S-1 filed under Rule 462(b), states the documents reviewed and assumptions relied upon, lists qualifications, gives the opinion paragraphs, and closes with a /s/ signature block and an explicit consent to be named in the registration statement and to the filing of the opinion as an exhibit.
Typically a one-page letter from the registrant's independent registered public accounting firm. It consents to the incorporation by reference of the firm's audit report — referenced by report date and by the prior S-1's 333-file number — into the new Rule 462(b) registration statement, and to the references to the firm in the prospectus under the heading "Experts." Additional consents (EX-23.2, EX-23.3, …) appear when more than one expert's report is incorporated by reference (for example, where a predecessor auditor is involved or where a separate industry expert is named).
The modern EDGAR filing-fee exhibit (also referred to colloquially as Exhibit 107) rendered as Inline XBRL HTML conforming to the SEC's Filing Fee Disclosure (FFD) taxonomy (e.g. xbrl.sec.gov/ffd/2025). The hidden <ix:header> block declares the submission type (ffd:SubmissnTp = S-1MEF), the filer's CIK, the prior registration file number to which the new securities are being added (ffd:RegnFileNb, e.g. 333-289152), and one xbrli:context per offering line plus a top-level c_report context. The visible body renders "CALCULATION OF FILING FEE TABLES" with "Table 1: Newly Registered and Carry Forward Securities", listing per security line item the security type, registered amount, maximum aggregate offering price, fee rate, fee amount, and any offset claims under Rule 457. The corresponding extracted XBRL instance (*_htm.xml) is listed under dataFiles[] but not bundled — the iXBRL HTML is the canonical fee artifact in the dataset.
Although the four exhibit types above (EX-5.x, EX-23.x, EX-FILING FEES) cover the vast majority of S-1MEF submissions, registrants occasionally attach additional textual exhibits — for example a power of attorney (EX-24), a tax counsel opinion (EX-8.1), or a letter regarding change in accountants (EX-16.1). When present these are preserved verbatim alongside the core exhibits, with their <TYPE> and documentFormatFiles[].type values intact.
A record includes the metadata.json manifest, the S-1MEF registration statement HTML, every legal opinion exhibit (EX-5.x), every consent exhibit (EX-23.x), the Inline XBRL EX-FILING FEES exhibit, and any other textual exhibits the registrant attached. The complete EDGAR SGML document wrappers around each HTML file are preserved, so consumers can recover exhibit type, sequence, on-disk file name, and EDGAR description directly from the document headers without parsing the manifest. All identifiers needed to join the record to other SEC datasets are present in the manifest: CIK, ticker symbols, the new 333-file number assigned to the S-1MEF, the SIC code, and the dashed accession number.
Image attachments (typically GRAPHIC documents of type JPG, GIF, or PNG referenced by <IMG SRC=...> tags inside the exhibits) are excluded from the bundled files. Their presence is still recorded by documentFormatFiles[] entries with type: "GRAPHIC", and the <IMG SRC> tags remain inside the HTML so the layout intent is preserved. Extracted XBRL instance documents corresponding to the EX-FILING FEES exhibit (the *_htm.xml artifacts EDGAR generates from the iXBRL) are listed in dataFiles[] but are not bundled — the iXBRL HTML in the document folder is the canonical fee-exhibit artifact in the dataset.
The substantive disclosures contained in the prior effective Form S-1 (business description, risk factors, MD&A, plan of distribution, prospectus narrative, financial statements, and notes) are not in the S-1MEF and therefore not in this dataset; they live in the related Form S-1 filing, incorporated by reference rather than reproduced. SEC correspondence, comment-and-response letters, and post-effective amendments on the parent S-1 are likewise outside the record.
Form S-1MEF has carried the same Rule 462(b) construction since its introduction in 1996 — a brief, immediately-effective registration statement bound to a prior effective S-1 — so the cover-page identification block, the 462(b) check-box election, the additional-securities description, and the signature page have been stable across the dataset's full date range.
The most material structural change is the modernization of the calculation-of-registration-fee table. For most of the form's history, this table was an in-document HTML or text table rendered directly on the cover page or page II-1 of the S-1MEF. Effective for filings on or after the SEC's 2022 filing-fee modernization rules (Release No. 33-10997), the fee disclosure migrated to a separately filed Inline XBRL exhibit (EX-FILING FEES, also called Exhibit 107) tagged against the FFD taxonomy. Modern S-1MEF records therefore incorporate the fee table by reference to the iXBRL exhibit rather than presenting it inline; older records present the fee table directly on the cover page.
Filer-status disclosures on the cover page have also evolved: the smaller reporting company check-box was added with the SEC's 2008 smaller reporting company rules, and the emerging growth company check-box was added with the JOBS Act in 2012, so cover pages from earlier filings will lack one or both of these elements. The auditor independence reference framework on EX-23 consents shifted from "registered public accounting firm" language only after Sarbanes-Oxley took effect in 2002.
Filings from the dataset's earliest period (February 1996 through roughly 2001) were submitted in plain ASCII / SGML with <TYPE> and <TEXT> wrappers but minimal HTML, so the on-disk artifacts for those records are short text-mode documents with hard line breaks and no styling. Through the early 2000s EDGAR's HTML adoption progressively shifted submissions into HTML inside the SGML wrapper, with richer inline styling as filing-agent toolchains (EdgarAgents, Novaworks, Toppan Merrill, Donnelley) replaced raw text submissions. The third major transition is the 2022 introduction of the Inline XBRL fee exhibit described above, which replaced the in-body fee table with a separate iXBRL HTML document and added a corresponding *_htm.xml instance to dataFiles[]. Across all eras the EDGAR SGML document wrapper format itself has been preserved, so the <DOCUMENT> / <TYPE> / <SEQUENCE> / <FILENAME> / <DESCRIPTION> / <TEXT> framing is a reliable parsing anchor for every record in the dataset.
Two file numbers always coexist in an S-1MEF record and must not be confused. The fileNo in metadata.json -> entities[] is the new 333-prefixed file number assigned to the S-1MEF itself. The ffd:RegnFileNb recorded inside the EX-FILING FEES iXBRL — and the file number named in the Rule 462(b) check-box on the registration-statement cover page — is the file number of the prior effective S-1 to which the additional securities are being added. By Rule 462(b) construction these two numbers are always different; the relationship between them is what links each S-1MEF record to its parent S-1 filing.
Because the substantive disclosures live in the parent S-1, machine extraction against an S-1MEF record yields registrant identification, the 462(b) election, signature metadata, and the structured fee-table line items, but not the underlying business, risk, or financial content. Pipelines that need those disclosures must follow the prior-S-1 file number to the related Form S-1 filing and join on CIK plus 333-file-number. The iXBRL fee exhibit is fully machine-readable: the FFD taxonomy supports programmatic extraction of the registered amount, maximum aggregate offering price, fee rate, fee amount, and any Rule 457(o) offsets without HTML scraping. The legality opinions and auditor consents, by contrast, are unstructured prose and require text parsing to extract counsel name, opinion scope, and report date.
S-1MEF records are uniformly short and exhibit-light, so individual accession folders are small (typically a few hundred kilobytes including manifest and exhibits), and document complexity does not scale with offering size — only the count of accession folders drives container size from one month to the next.
Each record is a Form S-1MEF registration statement filed on EDGAR by a domestic issuer that already has an effective Form S-1 covering the same offering and needs to register additional securities of the same class without staff review. The filer is always the same legal entity that filed the underlying effective S-1, acting as issuer of the registered securities. The form is signed by the registrant, its principal executive, financial, and accounting officers, and a majority of its directors, with any incremental legal opinions and expert consents attached as exhibits.
S-1MEF filers are a strict subset of S-1 filers, generally:
Foreign private issuers register on Form F-1 and use Form F-1MEF instead. S-3 shelf issuers use Form S-3MEF, and Form S-11 real estate issuers use Form S-11MEF. Investment companies registered under the Investment Company Act use the N-series registration regime and a separate Rule 462(b) mechanism.
S-1MEF is triggered by a late-stage decision to upsize an offering already proceeding under an effective S-1. The decision is almost always made at or immediately before pricing, in one of two patterns:
Securities Act Rule 462(b) caps additional registration via an MEF filing at 20% of the maximum aggregate offering price on the original effective registration statement. Upsizes within that ceiling can use S-1MEF; larger increases require a new registration statement or post-effective amendment, neither of which is immediately effective.
Form S-1MEF is filed under Securities Act Rule 462(b), which provides the "immediately effective" abbreviated registration mechanism for offerings already proceeding under a previously effective registration statement on the corresponding base form. The document is short by design: it identifies and incorporates the prior effective S-1 by reference, registers a stated additional amount of securities of the same class, includes a Calculation of Registration Fee table covering only those additional securities, carries the required signatures, and attaches any incremental opinions and consents. The filing is effective by operation of Rule 462(b) upon filing; it is not staff-reviewed and is not subject to acceleration. Rule 462(b) requires that the MEF be filed before confirmations of sale are sent for the additional securities and that the registration fee accompany the filing.
Timing is event-driven, not periodic. S-1MEF is filed on the day the offering is priced, after pricing demonstrates the need to upsize but before sales of the additional securities are confirmed to investors. Same-day automatic effectiveness is the operational reason the form exists, since a post-effective amendment would have to be declared effective by the staff and is incompatible with an active pricing timetable. To use the form, the filing must:
Amendments to S-1MEFs are uncommon and typically correct ministerial errors; the form presupposes a clean one-shot filing.
Form S-1MEF derives from the SEC's 1996 adoption of Rule 462(b), which created the immediately effective registration mechanism for offerings already under way. The MEF form variants (S-1MEF, S-3MEF, S-11MEF, F-1MEF, F-3MEF) were introduced at the same time to give issuers dedicated EDGAR form codes for Rule 462(b) filings. The earliest S-1MEF records on EDGAR, and in this dataset, date to February 1996.
Form S-1MEF occupies a narrow slot in the registration lifecycle: an issuer with a still-effective Form S-1 discovers at pricing that the deal will exceed the originally registered dollar amount, and Rule 462(b) permits a short companion registration statement that becomes effective on filing, registering up to 20% of additional aggregate offering price. The most useful comparisons are to the parent S-1, the 424B prospectus that records final terms, the parallel MEF forms for other registrant classes, and the amendment paths an issuer would otherwise have to use.
The full-disclosure Securities Act registration statement for domestic issuers that do not yet qualify for Form S-3, used most often for IPOs. S-1MEF depends on a prior effective S-1, incorporates it by reference, and registers only an incremental amount. The S-1 carries the prospectus, business description, risk factors, MD&A, financials, and full exhibit set; the S-1MEF is typically a cover page, a short fee table, signatures, and a few exhibits (legal opinions, consents). For deal-sizing or pricing analysis, both are needed: the S-1 supplies disclosure, S-1MEF marks the upsize event.
A 424B records the final priced terms of an offering whose registration is already effective; it does not register additional securities. S-1MEF and a 424B often hit EDGAR within hours of each other on pricing day, but their legal function differs: 424B is a prospectus delivery under an effective registration, while S-1MEF is itself a registration statement that expands the registered amount. Use 424B for price, share count, and underwriting terms; use S-1MEF to detect that the offering exceeded its original ceiling.
Form 424B prospectuses also include numbered subtypes such as 424B1 and 424B4 used in IPO pricing flows.
The structural twin of S-1MEF: same 20% cap, same automatic effectiveness, same single-purpose role under Rule 462(b). The difference is registrant population. S-3MEF rides on a Form S-3 (seasoned issuers eligible for short-form or shelf registration) and is typically associated with shelf takedowns and 424B5 supplements. S-1MEF rides on an S-1 and is concentrated in IPOs and follow-on offerings by issuers not yet S-3 eligible. The two populations rarely overlap.
The Rule 462(b) companion for foreign private issuers whose parent registration is Form F-1. Mechanically identical to S-1MEF, distinguished only by issuer domicile and the FPI disclosure regime governing the parent F-1. For cross-border IPO studies, S-1MEF and F-1MEF are complementary by jurisdiction.
The alternative path for changing a registration statement, including increasing the registered amount. Amendments do not become effective on filing; they generally require SEC review or staff acceleration, which is incompatible with same-day pricing-driven upsizing. S-1MEF exists to avoid that delay within the 20% cap. Increases beyond 20%, or substantive disclosure changes, must go through an amendment instead. POS AM and S-1/A datasets are broader in scope but not event-tied to pricing.
Rule 462 contains several immediate-effectiveness mechanisms. 462(a) governs automatic effectiveness for certain registration statements at the issuer's request; 462(c) and 462(d) cover narrow post-effective amendments (e.g., adding exhibits, non-substantive corrections). Only 462(b) authorizes a separate companion registration statement adding incremental securities; that is the slot S-1MEF fills. The others share the automatic-effectiveness mechanic but not the registering function.
S-1MEF is defined by the convergence of four features: it is a registration statement (not a prospectus or amendment); it is filed only under Rule 462(b), tied to a still-effective S-1, and capped at 20% of additional aggregate offering price; it becomes effective on filing with no SEC review; and its content is intentionally minimal because the substantive disclosure already lives in the parent S-1. The S-1 carries disclosure, the 424B carries priced terms, and S-1MEF is the time-stamped record of a same-day upsize within the Rule 462(b) ceiling. S-3MEF and F-1MEF extend the same pattern to other registrant classes without overlapping the S-1MEF population.
The Form S-1MEF Files Dataset serves a narrow set of users focused on offering sizing, fee mechanics, and last-minute capacity expansions on Rule 462(b) deals.
ECM syndicate and origination teams mine the calculation-of-registration-fee table for incremental share count and aggregate offering price, joined to the parent S-1 file number and effectiveness timestamp in metadata.json. Output: upsize base rates by sector and deal-size band, pitch-deck statistics on 462(b) headroom relative to book coverage, and live-deal sizing recommendations.
Capital-markets counsel use the corpus as a precedent library. Issuer counsel pull cover-page Rule 462(b) legends, signature blocks, and incorporation-by-reference language. Underwriter counsel review EX-5 opinions and EX-23 consents to determine what must be re-filed versus carried over from the predecessor S-1. Both sides verify the 20% cap against the parent registration's maximum aggregate offering price.
Sell-side and independent IPO analysts treat the MEF as a real-time demand signal. They sum the original S-1, the MEF fee table, and the 424B to compute true offered amount including any green-shoe, then feed revised float and post-IPO supply figures into initiation notes and pricing post-mortems.
League-table desks at data vendors and bank competitive-intelligence groups use the registrant CIK, parent S-1 file number, fee-table totals, and effective timestamp to attribute incremental deal volume to bookrunners and co-managers. Without MEF capture, credit understates the final deal. The 1996-onward history supports vintage-year reconstructions.
ECM and IPO reporters use the fee table and Rule 462(b) effectiveness clause to quote exact incremental dollars and shares within hours of filing. Editorial data teams aggregate MEF activity into longitudinal series for features on hot-IPO windows and demand spikes.
Finance researchers use MEF filings as a clean event marker for pricing-day upsize decisions, linking incremental capacity to first-day returns, offer-price revisions, and partial-adjustment patterns. Legal academics study how 462(b) practice evolved across decades using exhibit composition, signature conventions, and incorporation-by-reference behavior.
Engineers at data vendors, hedge funds, and fintech platforms use metadata.json as the join anchor between MEF accessions and S-1, 424B, Form 8-A, and EFFECT records. They parse fee tables from HTML and TXT submissions into normalized incremental-share and incremental-offering-price fields and use the predictable exhibit set (EX-5.1, EX-23.x) to test classifier logic.
Fee-analytics teams parse the calculation-of-registration-fee table and EX-FILING FEES exhibits to track 462(b) fees, reconcile fee-bearing capacity against the issuer's shelf, and study Rule 457(o) versus share-count fee bases. Issuer treasury groups benchmark their own fee computations against peer MEFs; regulatory-fee researchers build aggregate 462(b) revenue series across rate changes.
Document vendors serving law firms, banks, and corporate issuers index registrant identifiers, file numbers, exhibit lists, and cover-page statutory citations so subscribers can retrieve MEFs alongside the related S-1 and 424B as a single deal package. Complete historical coverage is required because the MEF is the sole authoritative artifact of the 462(b) upsize.
Broker-dealer syndicate compliance uses the MEF effective timestamp to confirm that incremental allocations sit within a registered offering at the moment of distribution. Market-surveillance groups align trade prints with the registered amount in force, especially when the MEF is filed in the same hour as pricing.
The Form S-1MEF corpus is the authoritative record of Rule 462(b) upsize events. The following workflows show how practitioners turn the manifest, fee exhibit, and cover-page elements into concrete outputs.
Pull every S-1MEF accession in a window, extract the registered amount and maximum aggregate offering price from the EX-FILING FEES iXBRL (FFD MaxAggtOfferingPric, share counts per offering line), and join to the parent S-1 via ffd:RegnFileNb to compute upsize-as-percent-of-original. Output: sector and size-band base rates for 462(b) usage, pitch-deck statistics on headroom utilization, and same-day "is this deal upsizing?" alerts keyed to the filedAt timestamp.
Reconstruct true deal volume by combining the parent S-1 base offering with the S-1MEF fee-table totals. The entities[].cik, parent RegnFileNb, and effectiveness timestamp let league-table desks attach incremental dollars to bookrunners and co-managers in the matching 424B prospectus. Without MEF capture, credit understates final deal size on every Rule 462(b) deal in the vintage.
Index cover-page Rule 462(b) legends, signature blocks, EX-5.1 / EX-5.2 opinion text, and EX-23.x consent language to build a precedent library. Issuer counsel filter by sic and stateOfIncorporation (e.g. Cayman SPAC precedents with Maples or Conyers EX-5.2 opinions); underwriter counsel reuse EX-23 consent paragraphs that reference the prior 333-file number. The <TYPE> SGML headers drive exhibit-type retrieval without filename pattern matching.
Parse the EX-FILING FEES iXBRL across the FFD-era population (filings on or after the 2022 modernization) into a normalized table: security type, registered amount, maximum aggregate offering price, fee rate, fee amount, and Rule 457 offsets per offering line. Output: 462(b) fee revenue series across rate changes, Rule 457(o) versus share-count base studies, and treasury benchmarking of issuer fee computations against peer MEFs.
Use the S-1MEF filedAt timestamp as a clean event marker for the issuer's pricing-day upsize decision. Join CIK to CRSP for first-day returns and to the parent S-1 / S-1/A sequence for offer-price revisions, then test partial-adjustment and demand-driven upsize hypotheses. The 1996-onward coverage supports decade-spanning panels and the format-stable cover page lets the 462(b) election be detected uniformly across eras.
Surveillance and best-execution teams ingest filedAt (ISO-8601 with offset) and the fee-table incremental share count to confirm that allocations after pricing sit inside a registered offering. Aligning trade prints to the moment the S-1MEF became effective by Rule 462(b) construction closes the gap between original S-1 capacity and final allocated size on upsized IPOs.
Index accessionNo, entities[].fileNo (the new 333- number), RegnFileNb (the parent), tickers[], and the exhibit list from documentFormatFiles[] so subscribers retrieve the S-1, the S-1MEF, and the 424B as a single deal package. The MEF is the sole authoritative artifact of the 462(b) upsize, so complete historical coverage is required for the package to be defensible.
Dataset Index JSON API: https://api.sec-api.io/datasets/form-s1mef-files.json
This endpoint returns the dataset metadata, including the name, description, last updated timestamp, earliest sample date, total record count, total size, form types covered, container format, and file types. It also returns the download URL for the full dataset archive and a list of all available container files with per-container metadata such as size, record count, last updated timestamp, and individual download URL. Poll this endpoint to detect which monthly containers were updated in the most recent refresh and to schedule incremental downloads. The endpoint does not require an API key.
Example response:
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{
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"datasetId": "1f13365b-9ae0-6982-a3af-d21f52721274",
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"datasetDownloadUrl": "https://api.sec-api.io/datasets/form-s1mef-files.zip",
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"name": "Form S-1MEF Files Dataset",
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"updatedAt": "2026-05-01T03:10:02.969Z",
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"earliestSampleDate": "1996-02-01",
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"totalRecords": 8082,
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"totalSize": 26163824,
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"formTypes": ["S-1MEF"],
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"containerFormat": "ZIP",
11
"fileTypes": ["TXT", "JSON", "HTML"],
12
"containers": [
13
{
14
"downloadUrl": "https://api.sec-api.io/datasets/form-s1mef-files/2025/2025-11.zip",
15
"key": "2025/2025-11.zip",
16
"size": 218450,
17
"records": 7,
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"updatedAt": "2025-11-28T21:14:08.000Z"
19
}
20
]
21
}
Download Entire Dataset: https://api.sec-api.io/datasets/form-s1mef-files.zip?token=YOUR_API_KEY
Downloads the complete Form S-1MEF Files Dataset as a single ZIP archive covering all filings from February 1996 to the present. Replace YOUR_API_KEY with your SEC API key. This endpoint requires authentication.
Download Single Container: https://api.sec-api.io/datasets/form-s1mef-files/2025/2025-11.zip?token=YOUR_API_KEY
Downloads one monthly container ZIP file instead of the full dataset. Containers are keyed by year and month (e.g., 2025/2025-11.zip), which is useful for fetching only newly added or updated months. Replace YOUR_API_KEY with your SEC API key. This endpoint requires authentication.
The dataset covers Form S-1MEF, a short, dependent registration statement filed under Securities Act Rule 462(b) that registers additional securities — capped at 20% of the maximum aggregate offering price of an already-effective Form S-1 — and becomes effective immediately upon filing without further SEC action.
One record corresponds to a single Form S-1MEF submission filed on EDGAR, identified by its 18-digit dashless accession number. On disk the record is a folder named after that accession number containing a metadata.json manifest plus the original EDGAR submission documents — the S-1MEF registration statement and every textual exhibit attached to it.
The filer is always the same domestic issuer that filed the underlying effective Form S-1, acting as the issuer of the registered securities. The population is concentrated in IPO-stage operating companies, special purpose acquisition companies (SPACs), follow-on issuers not yet S-3 eligible, smaller reporting companies, and emerging growth companies. Foreign private issuers use Form F-1MEF instead, and S-3 shelf issuers use Form S-3MEF.
Filing is event-driven, not periodic. An S-1MEF is filed on the day the offering is priced, after pricing demonstrates a need to upsize — either because the deal is oversubscribed and the issuer and underwriters increase deal size or price per share, or because underwriters exercise a green-shoe / over-allotment option that pushes aggregate offering value above the originally registered amount — but before sales of the additional securities are confirmed to investors.
The dataset covers Form S-1MEF filings from February 1996, when the SEC adopted Rule 462(b) and introduced the MEF form variants, through the present.
Records are packaged into monthly ZIP containers keyed YYYY/YYYY-MM.zip. Each accession folder contains a metadata.json manifest (JSON), the S-1MEF registration statement and exhibits as HTML files preserved inside their EDGAR SGML document wrappers, and TXT submission artifacts. Image binaries (JPG, GIF, PNG) referenced by the exhibits are not bundled, though their presence is recorded in documentFormatFiles[] as GRAPHIC entries.
Form S-1 is the full-disclosure parent registration statement carrying the prospectus, business description, risk factors, MD&A, financials, and full exhibit set. Form S-1MEF depends on a prior effective S-1, incorporates it by reference, and registers only an incremental amount of securities of the same class. The S-1 supplies the substantive disclosure; the S-1MEF is the time-stamped record of a same-day upsize within the Rule 462(b) 20% ceiling. Deal-sizing or pricing analysis typically requires both.