Insider Holdings Dedup

The default join of "all insider filings → sum of shares" overcounts
positions, often by 2–10x. The reason: SEC rules require multiple
related parties (funds, GPs, advisers, family members, trustees,
beneficial owners) to each file a 13D/G or Form 4 covering the SAME
underlying shares. Naive summation = fictional ownership numbers.

Core principle

Beneficial ownership is per-share, not per-filer. If three filers
report the same 1,000,000 shares because of a shared-voting-power
arrangement, the position is 1,000,000 — not 3,000,000.

The reverse is also true: separate parties may individually file
13D/G for distinct positions. You cannot blindly dedup either; you
must read the filings.

Where double-counting happens

Schedule 13D / 13G groups

A typical activist or institutional 13D group:

Filer 1: The fund (Limited Partnership)        — reports 1,000,000 sh
Filer 2: The fund's GP (LLC)                   — reports 1,000,000 sh
Filer 3: The investment manager / adviser      — reports 1,000,000 sh
Filer 4: The CEO / managing member (individual) — reports 1,000,000 sh

All four are filing the same SC 13D as a "group". The cover page of
each filing reports the same 1,000,000 shares. Naive sum = 4,000,000;
true position = 1,000,000.

Form 4 transaction filings

When an executive transacts through a trust, an LLC, or a family
office, multiple Form 4s may be filed for the same transaction:

• One by the executive
• One by the trust / LLC entity
• One by the family member (spouse / dependent) if reporting required

The transaction S 50,000 @ $10.00 may appear three times for what
is one sale.

13G institutional cluster

Vanguard, BlackRock, and similar issuers file at the asset-manager
level with multiple subsidiary entities. Same beneficial position,
multiple cover-page disclosures.

Dedup rules (in priority order)

1. Group identity (Item 2). If multiple 13D/G filings list each
   other as members of the same Section 13(d) group, treat as ONE
   position. The cover-page share counts of all members are typically
   identical (or report sub-allocations summing to the group total).

2. Shared voting / dispositive power. Schedule 13D Item 5 reports
   "sole" vs "shared" voting and dispositive power. When two filers
   each report shared power over the same N shares, those N shares
   appear once, not twice.

3. Family attribution. Spouse and dependent-children holdings
   are reported on the executive's Form 4 with footnotes ("shares
   held by spouse"). If the spouse files separately, dedup against
   the executive's filing.

4. Entity layering. Fund → GP → Adviser → Managing Member is one
   chain. If the chain reports the SAME shares at each level, dedup
   to the lowest economic owner (typically the fund / LP).

5. Joint reporters on a single 13D/G. The cover page lists all
   joint filers; the agreement under Item 6 typically attaches the
   joint filing agreement. Treat as one filing for sum purposes.

What is NOT a duplicate

These look similar but represent distinct positions:

• Different share classes. Class A and Class B common are distinct
  even when held by the same entity.
• Different Section 13(d) groups. Two unrelated activist funds
  each filing 13Ds at the same time on the same issuer are
  independent positions.
• Direct vs derivative holdings. A Form 4 reporting common stock
  • an option = two distinct economic exposures, not a duplicate.
• Old amendments superseded by new ones. When SC 13D/A (amendment
  3. supersedes SC 13D/A (amendment 2), only the latest counts toward
     current holdings — but for an event-time series, both matter.

Workflow when computing total insider holdings

1. Pull all 13D, 13G, 13D/A, 13G/A filings for the issuer in the
   target window.
2. Group filings by reported group identity (Item 2):
   • All filings citing each other on the cover page = one group.
   • Each group has ONE position (use the cover-page share count of
     any member; they should match).
3. For each independent group, compute the LATEST reported holding
   per amendment chain.
4. Compute sum across DISTINCT groups only.
5. Cross-check against atm-detection and recent 424B activity:
   total beneficial holdings + ATM-issued shares + outstanding shares
   should reconcile to total shares outstanding within ~5%.
   Larger gaps = missed dilution event or missed group.

Workflow when computing insider transaction volume (Form 4)

1. Pull all Form 4s for the issuer in the target window.
2. Group by transaction date + transaction code + share count +
   per-share price. Identical-tuple Form 4s filed by related parties
   are likely the same transaction reported through multiple filers
   (e.g., trust + executive + spouse).
3. Apply attribution: footnotes commonly say "shares held by [X]
   for the benefit of [Y]". The economic owner is one party.
4. Sum DEDUPED transactions only.

Special cases

• Form 144 (notice of intent to sell). Not an executed transaction;
  do not include in completed-sale tallies. The actual sale (if it
  occurs) shows up later as a Form 4. Treating 144s as Form 4s is
  one of the most common quant bugs. (See sec-filing-types.)
• 13F filings. Are NOT 13D/G — they cover institutional MANAGER
  holdings with a 45-day lag, no 5% ownership threshold, and no
  filer-group dedup logic applies. Don't mix 13F and 13D/G summation.
• CUSIP changes (reverse splits / mergers). If the issuer's CUSIP
  changed mid-window, ownership filings on the old CUSIP and new CUSIP
  are the same position; reconcile by ticker history, not by CUSIP.

Phrases that should trigger this skill

• "total insider holdings"
• "insider ownership %"
• "13D vs 13G dedup"
• "joint filers"
• "are these Form 4s duplicates"
• "13D group"
• "beneficial ownership reconciliation"

What this skill is NOT

This is not a beneficial-ownership extractor. It defines the
deduplication semantics so a downstream summation produces a real
number rather than a multi-counted fiction. Combine with
sec-filing-types for form context and lookahead-safety for
historical reconstruction of holdings.