Costco Wholesale Corp (COST) insider trading
Recent insider transactions reported to the SEC on Form 4 — directors and officers buying or selling their own company’s stock. Sourced directly from public SEC filings, latest filed Oct 14, 2026.
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- Filings shown
- 11
- Open-market buys
- 0
- Open-market sells
- 3
Counts cover the 11 most recent Form 4 filings Tradune holds for COST (filed Jul 14 – Oct 14, 2026); the score below covers only the trailing 90 days (0 buys, 3 sells). No completed check of COST's Form 4 list on SEC EDGAR is on record yet; the latest COST filing Tradune holds was filed Oct 14, 2026. This is not guaranteed to be the complete record — see COST's full Form 4 filing history on SEC EDGAR.
Open-market activity, last 90 days
Purchases (Form 4 code P) and sales (code S) on the 10 filings Tradune holds for COST filed Sep 14 – Oct 14, 2026. Grants, exercises, tax withholding and the other Form 4 transaction codes are left out.
3 open-market sales by Rule 10b5-1 checkbox
- On filings with the 10b5-1 box checked
- 0 sales· 0 sh
- checkbox disclosed
- On filings with the box not checked
- 3 sales· 4,101 sh
- not proof that no plan exists
- Not comparable
- 0 sales· 0 sh
- filed before Apr 1, 2023, or no checkbox value in the filing data
Counts are Form 4 lines as filed. The checkbox is one per filing, so every sale on a filing with the box checked is counted there even if only some of its transactions were under a plan; it records what the filer disclosed, and the three categories are not a judgement about why a sale was made.
| Insider | Buys | Sells | Shares bought | Shares sold | Value |
|---|---|---|---|---|---|
| Claudine AdamoExecutive Vice President | 0 | 1 | — | 2,200 | −$2,015,046 |
| William Richard WilcoxExecutive Vice President | 0 | 1 | — | 1,100 | −$1,054,026 |
| Caton FratesSr. Executive Vice President | 0 | 1 | — | 801 | −$733,328 |
Value = shares × the price reported on each Form 4 (+ purchases, − sales); every open-market line in this window disclosed a price.
Summarises ~90 days of public SEC Form 4 activity — more distinct buyers, officer involvement and net buying score higher. A description of filing activity, not a rating or buy signal. How this score is computed →
How to read this: an open-market purchase (Form 4 code P) is a buy at the market price with the insider’s own money, as opposed to a grant, award or option exercise; an open-market sale is code S. When two or more distinct insiders report open-market purchases in the same 90-day window, this site labels that a cluster — a definition, not a forecast; see insider cluster buying. “Held after” is Form 4 Table I column 5; “Change” = shares ÷ holdings before the trade (held after − shares for an acquisition, held after + shares for a disposition).
Insider Buying at COST
No open-market insider purchases (Form 4 code P) were reported for COST between Jul 14, 2026 and Oct 14, 2026. The filings below may include other transaction types — sales, grants, option exercises, and tax withholding — shown for completeness; they are not open-market purchases.
Recent Form 4 filings
Source: SEC EDGAR Form 4 · transaction codes explained
| Transaction | Shares | Price | Held after | Change† | Date |
|---|---|---|---|---|---|
| Open-market sale 10b5-1 box not checked | 1,100 | $958.21 | 3,094 | −26% | Oct 13, 2026 |
† change in this filer’s own reported holding line (Form 4 Table I, col. 5), not of total company ownership; small prior holdings produce large percentages, so under 100 shares the prior holding is shown instead.
“10b5-1 box checked” = the filer checked the Form 4 box stating that a transaction on the filing was made under a plan intended to satisfy Rule 10b5-1(c); “10b5-1 box not checked” = the box was left blank, which does not prove that no plan exists. The box applies to Form 4s filed from April 1, 2023; older filings, and boxes we could not read, carry no tag. What the 10b5-1 box means.
| Transaction | Shares | Price | Held after | Change† | Date |
|---|---|---|---|---|---|
| Open-market sale 10b5-1 box not checked | 801 | $915.93 | 7,912 | −9.2% | Sep 29, 2026 |
| Transaction | Shares | Price | Held after | Change† | Date |
|---|---|---|---|---|---|
| Open-market sale 10b5-1 box not checked | 2,200 | $915.93 | 7,134 | −24% | Sep 29, 2026 |
| Transaction | Shares | Price | Held after | Change† | Date |
|---|---|---|---|---|---|
| Grant / award | 4,129 | — | 6,129 | +206% | Sep 10, 2026 |
| Tax withholding | 1,935 | $902.38 | 4,194 | −32% | Sep 10, 2026 |
| Transaction | Shares | Price | Held after | Change† | Date |
|---|---|---|---|---|---|
| Grant / award | 4,129 | — | 12,376 | +50% | Sep 10, 2026 |
| Tax withholding | 1,696 | $902.38 | 10,680 | −14% | Sep 10, 2026 |
| Transaction | Shares | Price | Held after | Change† | Date |
|---|---|---|---|---|---|
| Tax withholding | 1,562 | $902.38 | 14,246 | −9.9% | Sep 10, 2026 |
| Grant / award | 4,552 | — | 15,808 | +40% | Sep 10, 2026 |
| Transaction | Shares | Price | Held after | Change† | Date |
|---|---|---|---|---|---|
| Tax withholding | 936 | $902.38 | 48,030 | −1.9% | Sep 10, 2026 |
| Grant / award | 4,129 | — | 48,966 | +9.2% | Sep 10, 2026 |
| Transaction | Shares | Price | Held after | Change† | Date |
|---|---|---|---|---|---|
| Grant / award | 4,129 | — | 8,057 | +105% | Sep 10, 2026 |
| Tax withholding | 1,459 | $902.38 | 6,598 | −18% | Sep 10, 2026 |
| Transaction | Shares | Price | Held after | Change† | Date |
|---|---|---|---|---|---|
| Grant / award | 4,552 | — | 10,367 | +78% | Sep 10, 2026 |
| Tax withholding | 1,654 | $902.38 | 8,713 | −16% | Sep 10, 2026 |
| Transaction | Shares | Price | Held after | Change† | Date |
|---|---|---|---|---|---|
| Grant / award | 4,129 | — | 10,250 | +67% | Sep 10, 2026 |
| Tax withholding | 917 | $902.38 | 9,334 | −8.9% | Sep 10, 2026 |
| Transaction | Shares | Price | Held after | Change† | Date |
|---|---|---|---|---|---|
| Gift | 5,249 | — | — | — | Jul 10, 2026 |
Insider filings reported around the same time
Other companies whose most recent Form 4 was filed closest to COST's (Oct 14, 2026).
Frequently asked about COST insider activity
How many insiders bought COST stock in these Form 4 filings?
No open-market purchases (Form 4 code P) of COST shares were reported by Costco Wholesale Corp insiders between Jul 14, 2026 and Oct 14, 2026. The 11 filings shown on this page cover other transaction types — sales, grants, option exercises, and tax withholding.
Who filed the most recent Form 4 for COST?
The most recent Form 4 on this page was filed by William Richard Wilcox (Executive Vice President) on Oct 14, 2026, reporting 1 transaction. The original document is linked from the filing list above on SEC EDGAR. Amended filings (Form 4/A) may later revise reported figures.
What was the largest open-market COST insider sale shown?
The largest open-market sale among the filings shown was 2,200 COST shares at $915.93 (about $2,015,046) by Claudine Adamo (Executive Vice President) on Sep 29, 2026. Value is shares × the price reported on the Form 4; its Rule 10b5-1 box is not checked.
New to Form 4s? The transaction codes, the 90-day window and the 0–100 score are defined on the insider-activity score methodology page.
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Track COST insider filings free →This score summarizes SEC Form 4 filing activity over the trailing 90 days. It is descriptive, not predictive — not a rating, recommendation, or investment advice. Data: SEC EDGAR (public domain), as filed; amendments may revise figures. Tradune is not a registered investment adviser.
Data as filed; amended filings (Form 4/A) may revise figures. Sales may occur under prearranged Rule 10b5-1 trading plans.