MKS CEO has 2,157 shares withheld for FICA taxes

Each restricted stock unit represents a contingent right to receive one MKS Inc. common share.

Available on EDGAR 11/03/2026 - 04:42 PM EST Accepted by SEC EDGAR 11/03/2026 - 04:41 PM EST Learn about SEC filing dates

Rhea-AI Filing Summary

MKS Inc. President & CEO and director John Tseng-Chung Lee reported converting portions of his 2025 and 2026 restricted stock unit awards into 1,479 and 679 common shares, respectively, on October 30, 2026; both award portions were accelerated to satisfy FICA taxes. On that date, 2,157 common shares were withheld for FICA taxes at $202.04 per share.

Insider Trade Summary

2,157.445 shares exercised/converted

Exercise 5 txns

Insider Lee John Tseng-Chung

Role President & CEO

Type	Security	Shares	Price	Value
Exercise	Restricted Stock Unit F1, F3	1,478.864	--	--
Exercise	Restricted Stock Unit F1, F4	678.581	--	--
Exercise	Common Stock F1	1,478.864	--	--
Exercise	Common Stock F1	678.581	--	--
Tax Withholding	Common Stock F2	2,157.445	$202.04	$436K

Holdings After Transaction: Restricted Stock Unit — 82,670.676 contracts (Direct); Common Stock — 134,776.2667 shares (Direct)

Footnotes (4)

1. F1. Each restricted stock unit (RSU) represents the contingent right to receive one share of common stock of MKS Inc.
2. F2. Shares used to satisfy FICA taxes.
3. F3. Portion of 2025 RSU Award accelerated to satisfy FICA taxes.
4. F4. Portion of 2026 RSU Award accelerated to satisfy FICA taxes.

Key Figures

Common shares from 2025 RSU award: 1,479 common shares Common shares from 2026 RSU award: 679 common shares Shares withheld for FICA taxes: 2,157 common shares +1 more

4 metrics

Common shares from 2025 RSU award 1,479 common shares Converted on October 30, 2026

Common shares from 2026 RSU award 679 common shares Converted on October 30, 2026

Shares withheld for FICA taxes 2,157 common shares October 30, 2026

Withholding price $202.04 per share October 30, 2026

Key Terms

Restricted Stock Unit, FICA taxes, contingent right

3 terms

Restricted Stock Unit financial

"Each restricted stock unit (RSU) represents the contingent right"

A restricted stock unit is a promise from a company to give an employee shares of stock after certain conditions are met, like staying with the company for a set amount of time. It’s like earning a bonus that turns into company stock once you’ve proven your commitment, making it a way to motivate and reward employees.

FICA taxes financial

"Shares used to satisfy FICA taxes."

contingent right financial

"represents the contingent right to receive one share"

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How many MKSI shares were withheld for FICA taxes?

John Tseng-Chung Lee reported withholding 2,157 common shares for FICA taxes at $202.04 per share on October 30, 2026.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Lee John Tseng-Chung

(Last) (First) (Middle)

C/O MKS INC.

2 TECH DRIVE

(Street)

ANDOVER MASSACHUSETTS 01810

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
MKS INC [ MKSI ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	President & CEO

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
10/30/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	10/30/2026		M		1,478.864	A	(1)	136,255.1307	D
Common Stock	10/30/2026		M		678.581	A	(1)	136,933.7117	D
Common Stock	10/30/2026		F(2)		2,157.445	D	$202.04	134,776.2667	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Restricted Stock Unit	(1)	10/30/2026		M			1,478.864	(3)	(3)	Common Stock	1,478.864	(1)	83,349.257	D
Restricted Stock Unit	(1)	10/30/2026		M			678.581	(4)	(4)	Common Stock	678.581	(1)	82,670.676	D

Explanation of Responses:

1. Each restricted stock unit (RSU) represents the contingent right to receive one share of common stock of MKS Inc.

2. Shares used to satisfy FICA taxes.

3. Portion of 2025 RSU Award accelerated to satisfy FICA taxes.

4. Portion of 2026 RSU Award accelerated to satisfy FICA taxes.

	/s/ M. Kathryn Rickards, attorney-in-fact	11/03/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)