# Insider Dedup > Use when aggregating beneficial-ownership filings (Schedule 13D, 13G, amendments) or insider transaction filings (Form 3, 4, 5, 144) to compute total insider holdings or insider activity. Defines the joint-filer, group, and shared-voting-power deduplication rules so that a single position is not double-counted across N filers. - Skill: `jefrnc/insider-dedup` (Agent Skill) - Install (CLI): `npx skillmds@latest add jefrnc/insider-dedup` - Raw SKILL.md: https://api.skillmd.com/api/skills/jefrnc/insider-dedup/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - License: MIT - Author: jefrnc (https://skillmd.com/u/jefrnc) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/jefrnc/insider-dedup --- # 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.