About
How we clean the glass
Glass Cleaner turns the insider filings Costco's officers, directors and large holders send to the SEC into a plain-English feed: who sold, who bought, who was granted shares, and how much.
Where the data comes from
- Every Form 3, 4 and 5, amendments included, filed for Costco Wholesale Corporation (COST, SEC CIK 0000909832) since 12/2/21, read from SEC EDGAR.
- Values are shown as filed: the exact shares, prices and dates in each filing's XML. Every row links to its filing page, and every filing page links to the SEC original.
- Nothing here comes from anywhere but those public filings. Reporting owners' addresses are in the filings but are never stored or shown.
What counts as sold and bought
Only open-market or private sales (code S) and purchases (code P) of the stock itself count toward the Sold and Bought lines. A grant, a vesting, tax withholding or a gift is never counted as a sale: each gets its own label, and grants, withholding and gifts get their own lines on The Receipt.
Net flow is the dollars bought minus the dollars sold, where dollars are shares × price per share as filed. A negative net flow means insiders sold more than they bought in that period. It says nothing about why.
Periods count trades by trade date, not filing date. Quarters follow Costco's fiscal calendar: 52 or 53 weeks ending on the Sunday nearest August 31, with quarters of 12, 12, 12 and 16 (or 17) weeks.
What the labels mean
| Code | SEC meaning | Label here | In Sold or Bought? |
|---|---|---|---|
| S | Open market or private sale | Sold | Yes: sold |
| P | Open market or private purchase | Bought | Yes: bought |
| F | Paid the exercise price or tax by delivering or withholding shares | Withheld for taxes | No: its own line |
| A | Grant or award under Rule 16b-3(d) | Granted | No: its own line |
| M | Exercise or conversion of a derivative exempted under Rule 16b-3 | Vested or exercised | No |
| C, X, O | Conversion; in-the-money exercise; out-of-the-money exercise | Exercised or converted | No |
| G | Bona fide gift | Gifted | No: its own line |
| D | Disposition to the issuer under Rule 16b-3(e) | Returned to company | No |
| W | Acquired or disposed of by will or the laws of descent | Inheritance transfer | No |
| J, K, I, L, U, Z, E, H, V | Other, swaps, discretionary, small acquisitions, tender, voting trust, expirations, voluntary early report | Other (see footnote) | No |
Codes from the SEC's Form 4 General Instructions.
The tags on a row
- Pre-Planned (10b5-1): the filing's 10b5-1 box is checked, or, on filings from before that box existed (April 2023), a footnote mentions a 10b5-1 plan.
- Indirect: shares held through a trust, family member, 401(k) or entity, with the filing's own description.
- Amended: the row comes from an amendment (Form 3/A, 4/A or 5/A).
- Late: the filing itself marks the transaction as reported late.
Amendments
An amendment often restates only the lines it corrects. So an amendment replaces just the matching lines of the filing it amends (same table, date, code and ownership), and the rest of that filing stands. Replaced lines stay on the original filing's page, marked Restated, and are left out of every total.
Missing prices
Some lines have no price, or a $0 price: grants of restricted stock units and gifts, for example. Their value shows as “—” with “No price on filing”, and they never add $0 to a total. No outside stock-price source is used.
Updates
Last updated 11/5/26, 9:45 AM PT. The most recent filing is from 10/27/26. Right now: 284 filings from 31 insiders, 508 trades, and 21 lines restated by amendments.
2 amendments amend a filing from before our history starts, so their lines stand as filed: 0001209191-21-067442, 0001209191-21-067463.
Update log
| Run | New filings | Lines read | Errors | Warnings |
|---|---|---|---|---|
| 11/4/26, 9:26 AM PT | 89 | 99 | 0 | 1 |
The fine print
Not affiliated with or endorsed by Costco Wholesale Corporation. Data from SEC EDGAR, shown as filed. Not investment advice.
Filings say what happened, not why. Insiders sell for many ordinary reasons: taxes, diversification, a house. Nothing here suggests anyone did anything wrong, and nothing here is advice to buy or sell anything.