SEC Accession Numbers: What That 18-Digit Code Actually Means

If you've ever opened a 13F filing on EDGAR, looked at a Form 4 cross-reference, or chased a Schedule 13D footnote in a corporate dispute, you've seen something like this: 0001067983-25-000123. Eighteen digits. Three dash-separated segments. SEC documents call it an accession number, and it is the canonical primary key for every filing the SEC has ever received via the EDGAR electronic system. Understanding what each segment encodes makes the SEC record materially more navigable.

Across this platform, accession numbers appear on filer profile pages, in 13D/G tables, in Form 4 insider records, and in research article citations. Knowing how to decode them lets you jump directly from any 13F Insight reference back to the SEC primary source.

The Three Segments

Take a worked example: 0001067983-25-000123.

So 0001067983-25-000123 reads as: the 123rd filing submitted by Berkshire Hathaway (CIK 1067983) during calendar year 2025.

What the Numbers Tell You

The CIK (Central Index Key)

CIK is the SEC's permanent identifier for any entity that has ever filed anything with EDGAR — companies, fund families, insiders, even SPAC sponsors. CIKs are assigned sequentially as entities first file, so older entities have lower CIKs. BlackRock, Inc. sits at CIK 2012383 (a relatively recent registration of a specific BlackRock entity); State Street Corp sits at CIK 93751 (registered in the 1970s).

Note that CIK is the filing entity, not the subject of the filing. A 13F filed by FMR LLC about its holdings of Apple has the filer CIK (FMR LLC's, 315066) in the accession number — not Apple's. A Schedule 13D filed by an activist about a target company has the activist's filer CIK, not the target's.

The Year

Two-digit year. The 2025 calendar year is 25; 2026 is 26. The year is when the filing was submitted, not when the underlying reporting period closed. A Form 4 transaction dated 2024-12-30 that was filed in early January 2025 will have 25 in its accession number despite reporting a 2024 transaction.

The Sequence Number

Six-digit zero-padded, unique within filer + year. The number does not encode form type, subject company, or any other metadata — it's purely a within-filer-year counter incremented as the filer (or their filing agent / EDGAR submission service) submits each filing. So 000001 is the first filing of the year for that filer; 000123 is the 123rd; 012000 would be the 12,000th. Large brokers and dealers that file thousands of Form 4s annually can reach sequence numbers in the five-digit range.

Why Accession Numbers Beat Plain URLs

SEC EDGAR exposes filings via URLs like https://www.sec.gov/Archives/edgar/data/1067983/000106798325000123/... — but those URLs are constructed from the accession number components. If you have the accession number you can always construct the URL deterministically. The reverse is not true: the URL doesn't make the parts as obvious. Once you can decode accession numbers, you can:

• Jump directly from a 13F Insight article citation back to the SEC primary source using only the printed accession code.
• Cross-reference filings across the SEC's full-text search (efts.sec.gov) — accession numbers are first-class identifiers.
• De-duplicate filings programmatically — two filings with the same accession number are the same filing, full stop.
• Trace amendment chains — Form 13F-HR/A amendments reference the original 13F-HR by accession number in their cover page.

Common Accession-Number Patterns

Once you've decoded a few hundred accession numbers, certain filers' patterns become familiar:

• Filing agents — Many smaller filers use third-party filing agents (Computershare, Toppan Merrill, etc.). Those agents have their own CIKs and their own sequence-number streams. An accession number starting with a filing agent's CIK doesn't tell you which underlying issuer the filing concerns — you have to open the filing to see.
• Very high sequence numbers — Filers in the 10,000+ range typically include the SEC's largest broker-dealer entities, the largest banks, and a handful of mass-Form-4 filing complexes. Citadel Securities, Susquehanna, and the major prime brokers all sit in this range.
• Year-over-year continuity — A filer's sequence number resets each calendar year. A drop in volume year-over-year (from 000800 at year-end 2024 to 000200 at year-end 2025) can indicate organizational change, M&A activity, or a regulatory filing reduction.

Special Cases

Paper Filings

Pre-EDGAR (before 1993 broadly) and a small set of post-EDGAR paper filings do not have accession numbers in the modern 18-digit format. Some carry legacy paper-filing identifiers. Most analyses on this platform do not surface those because pre-1993 institutional ownership data is not publicly retrievable from EDGAR.

Withdrawn Filings

A filing can be withdrawn (Form 25 for delisting, Form 15 for deregistration). The original accession number persists in the record; the withdrawal is a separate accession number that references the original.

EDGAR Outages

The SEC has had a small number of EDGAR outages over the years (notably in late 2023). Filings submitted during outages may receive non-standard sequence numbers or backdated accession numbers. These are rare and documented in SEC public statements.

Worked Example — Following the Vanguard Reshuffle

The recent Vanguard reporting-entity reshuffle referenced three specific accession numbers:

• 0002100119-26-000520 — VANGUARD CAPITAL MANAGEMENT LLC (CIK 2100119), filed in 2026, sequence 520. This is the 520th filing submitted by Vanguard Capital Management LLC during calendar 2026.
• 0000102909-26-001322 — VANGUARD GROUP INC. (CIK 102909), filed in 2026, sequence 1322. The 1322nd filing — a much higher sequence reflecting Vanguard Group Inc.'s decades-long filing history and the many fund-level reportings made under that entity.
• 0000093751-25-000602 — STATE STREET CORP (CIK 93751), filed in 2025, sequence 602.

Each of those is reconstructable into a direct EDGAR URL. The leading-zero padding on the CIK and sequence components is what makes them lexicographically sortable — important for any system that sorts filings chronologically inside a single filer.

Quick Reference

For more on the SEC filing types that produce these accession numbers (13F-HR, 13F-HR/A, Schedule 13D, Schedule 13G, Form 4, Form 5, Form 8-K, Form 10-Q, Form 10-K), see the 13F Insight learn library. To trace a specific accession number to its source, the SEC filings hub resolves the cross-references automatically.