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AlphaScala
SEC Form 4 transaction code

Form 4 Code S: Open Market or Private Sale

Code S marks a sale of the company’s stock, or of a derivative, in the open market or in a private transaction.

“Open market or private sale of non-derivative or derivative security”
SEC Form 4, General Instruction 8 (Transaction Codes), under “General Transaction Codes”. Form 4 and instructions (PDF, sec.gov)

How often code S appears in real filings

Share of transaction rows
38.4%
19,214 of 50,023 rows, 1st most common
Filings with a code S row
35.0%
7,022 of 20,089 filings
Companies
1,385
of 2,099 in the sample
Median days, trade to filing
2
calendar days

18,890 of the rows are in Table I (non-derivative securities) and 324 in Table II (derivative securities). 65.7% of code S rows are on filings with the Rule 10b5-1 plan box checked.

Sample: 50,023 transaction rows in 20,089 Form 4 and 4/A filings filed Jul 23 – Oct 21, 2026 by insiders of 2,099 companies with an AlphaScala stock page. Rows are counted as filed; see how the codes are counted.

SEC Form 4 filings as of Oct 21, 2026

Reading code S on a Form 4

Many sales follow an exercise or a vesting reported on the same Form 4. An executive exercises options (code M) and sells some or all of the new shares the same day, or sells shares that have just vested. The filing shows both legs, so the sale can be read against what was received and what is left.

Since April 2023 Form 4 has a checkbox for transactions made under a contract, instruction or written plan intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). A sale on a filing with that box checked was scheduled under such a plan, and General Instruction 10 asks the filer to give the date the plan was adopted.

Not every disposal is a sale. Shares the company withholds to pay tax on vesting are code F, gifts are code G, shares handed back to the company are code D and shares tendered into a takeover offer are code U. Counting those rows as sales overstates insider selling, and AlphaScala’s insider tables count only code S as a sale.

Code S in real filings

Recent Form 4 lines coded S, chosen from the newest filings in the sample, one company each. Figures are as filed; each links to the filing on sec.gov.

SNOWSnowflake Inc.

Filing on sec.gov
Insider
Slootman Frank, Director
Transaction date
Oct 19, 2026
Filed
Oct 21, 2026
Table
I, non-derivative
Shares
82,420
Price
$317.36
Shares × price
$26.2M
Held after
79,142 (direct)
  • Slootman Frank (Director) sold 82,420 shares at $317.36 per share, about $26.2M.
  • Shares held after the transaction: 79,142, held directly.
  • The Rule 10b5-1 box is checked on this filing: a transaction on it was made under a plan intended to meet Rule 10b5-1(c).
  • The same filing also reports 9 code S rows (217,580 shares) and 2 code M rows (600,000 shares and derivative securities).
  • Filed 2 days after the transaction date.

MUMICRON TECHNOLOGY INC

Filing on sec.gov
Insider
Deboer Scott J, Pres. & Chief Tech & Prod Offr
Transaction date
Oct 16, 2026
Filed
Oct 20, 2026
Table
I, non-derivative
Shares
28,444
Price
$900.00
Shares × price
$25.6M
Held after
147,531 (direct)
  • Deboer Scott J (Pres. & Chief Tech & Prod Offr) sold 28,444 shares at $900.00 per share, about $25.6M.
  • Shares held after the transaction: 147,531, held directly.
  • The Rule 10b5-1 box is checked on this filing: a transaction on it was made under a plan intended to meet Rule 10b5-1(c).
  • The same filing also reports 2 code S rows (100.57 shares).
  • Filed 4 days after the transaction date.

TALOTALOS ENERGY INC.

Filing on sec.gov
Insider
Control Empresarial de Capitales S.A. de C.V., 10%+ Owner
Transaction date
Oct 19, 2026
Filed
Oct 21, 2026
Table
I, non-derivative
Shares
2,141,590
Price
$18.01
Shares × price
$38.6M
Held after
24,500,000 (direct)
  • Control Empresarial de Capitales S.A. de C.V. (10%+ Owner) sold 2,141,590 shares at $18.01 per share, about $38.6M.
  • Shares held after the transaction: 24,500,000, held directly.
  • Filed 2 days after the transaction date.

Codes read alongside S

Questions about these codes

How common is code S on Form 4?

In AlphaScala’s sample of 50,023 Form 4 transaction rows filed Jul 23 – Oct 21, 2026, code S made up 38.4% of rows (19,214) and appeared on 35.0% of filings (7,022 of 20,089). It was the 1st most common of the 16 codes found.

Is code S the same as code F?

No. S is a sale in the open market or in a private transaction. F is "payment of exercise price or tax liability by delivering or withholding securities" tied to a Rule 16b-3 award: the company keeps shares to cover the tax or exercise price, and the insider does not sell them in the market.

What does the 10b5-1 box mean on a code S sale?

The filer checks it to indicate that a transaction on the form "was made pursuant to a contract, instruction or written plan" intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). The box has been on Form 4 since April 2023, and the filer gives the plan’s adoption date in the explanation of responses.

Why do insiders sell stock?

Form 4 does not ask. Sales can pay tax on vested stock, fund an option exercise, diversify a concentrated holding or carry out a plan adopted months earlier. The filing shows the size and price of the sale and the holdings left afterwards, and footnotes sometimes add context.

Definition: SEC Form 4, General Instruction 8 (sec.gov). Examples and counts: AlphaScala's copy of SEC EDGAR Form 4 filings. See all 20 Form 4 transaction codes, insider cluster buys and our methodology.

Educational reference only, not investment advice. Insider transactions have many motives and a Form 4 does not record them. See our risk disclaimer.