Masimo (MASI) removes unsold S-3 securities after Danaher merger

Rhea-AI Filing Summary

Masimo Corporation deregisters all unsold securities registered on its Form S-3 following the completion of a merger with Danaher Corporation.

The post-effective amendment states that, pursuant to the Agreement and Plan of Merger dated February 16, 2026, Merger Sub merged with and into Masimo on June 10, 2026, the registrant became a wholly owned subsidiary of Danaher, and all offerings under Registration No. 333-285240 have been terminated and removed from registration.

Insights

Corporate Transactions Attorney

Post-effective amendment removes unsold shelf securities after a closing merger.

The filing is a standard post-effective amendment to a Form S-3 that deregesters unsold securities under Registration No. 333-285240, reflecting the merger closing described in the agreement dated February 16, 2026.

Key legal effect: the registration statement is terminated and effectiveness is ended; related rights under that registration no longer support public sales. Any remaining contractual rights or obligations should be reviewed in the Merger Agreement (Exhibit 2.1 referenced).

Securities Capital Markets Analyst

This is an administrative deregistration tied to a corporate acquisition, not a new capital raise.

The amendment states that offerings registered under the Form S-3 were terminated as a result of the Merger closing on June 10, 2026. No offering size, pricing, or proceeds are disclosed in the amendment.

Operational consequence: the shelf registration no longer provides capacity for future public sales under that registration number; subsequent filings from the combined company would govern any new offerings.

Key Figures

Registration Number: 333-285240 Merger closing date: June 10, 2026 Merger Agreement date: February 16, 2026 +1 more

4 metrics

Registration Number 333-285240 Form S-3 referenced in the post-effective amendment

Merger closing date June 10, 2026 Date Merger Sub merged into the Registrant

Merger Agreement date February 16, 2026 Agreement and Plan of Merger dated

Original S-3 filing date February 25, 2025 Date the Registration Statement was filed

Key Terms

post-effective amendment, deregister, Registration Statement on Form S-3, Agreement and Plan of Merger

4 terms

post-effective amendment regulatory

"to this Post-Effective Amendment to the Registration Statement"

A post-effective amendment is an official update to a securities registration document filed after that document has become effective with regulators; it corrects, adds or replaces information about the securities, the company, or an offering. Investors care because it keeps the legal record current and can change what is being sold or the rights attached to shares — like getting a revised product manual after a launch that may affect value or use.

deregister regulatory

"to deregister all securities registered pursuant to the Registration Statement"

Deregister is the act of removing a company’s securities from a public regulatory registry or ending their listing on a stock exchange; think of it like taking a car off public roads so it no longer needs public inspections. For investors, deregistration matters because it usually reduces required public disclosures, can make shares harder to buy or sell, and increases uncertainty about the company’s finances and governance due to lower transparency and liquidity.

Registration Statement on Form S-3 regulatory

"Post-Effective Amendment to Form S-3 REGISTRATION STATEMENT"

A registration statement on Form S‑3 is a short, standardized filing a qualified public company uses to register new securities with regulators so they can be sold to investors; think of it as a pre-approved, reusable permission slip that speeds up future offerings. It matters to investors because it lets the company raise money more quickly and cheaply — which can fund growth or pay debt — but may also lead to share dilution or change in ownership, so it affects value and liquidity.

Agreement and Plan of Merger legal

"pursuant to the terms of the Agreement and Plan of Merger"

An Agreement and Plan of Merger is a formal document where two companies agree to combine into one, outlining how the process will happen. It’s like a step-by-step plan for merging, and it matters because it shows both sides have agreed on the details before the official transition takes place.

Offering Details

shelf

Offering

Offering Type shelf

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As filed with the Securities and Exchange Commission on June 10, 2026

Registration No. 333-285240

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

Post-Effective Amendment No. 1

to

Form S-3

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

MASIMO CORPORATION

(Exact name of registrant as specified in its charter)

Delaware		33-0368882
(State or other jurisdiction of incorporation)		(IRS Employer Identification No.)

52 Discovery
Irvine, California 92618
(949) 297-7000

(Address, including zip code, and telephone number, including area code of principal executive offices)

Micah Young

EVP, Chief Financial Officer

Masimo Corporation

52 Discovery

Irvine, California 92618

(949) 297-7000

(Name and address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Daniel Wolf, P.C.

David M. Klein, P.C.

Brian H. Junquera

Kirkland & Ellis LLP

601 Lexington Avenue

New York, New York 10022

(212) 446-4800

Approximate date of commencement of proposed sale to the public: Not applicable. Removal from registration of securities that were not sold pursuant to the above referenced registration statement.

If the only securities being registered on this Form are being offered pursuant to dividend or interest reinvestment plans, please check the following box:  ¨

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, other than securities offered only in connection with dividend or interest reinvestment plans, check the following box:  ¨

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ¨

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ¨

If this Form is a registration statement pursuant to General Instruction I.D. or a post-effective amendment thereto that shall become effective upon filing with the Commission pursuant to Rule 462(e) under the Securities Act, check the following box.  x

If this form is a post-effective amendment to a registration statement filed pursuant to General Instruction I.D. filed to register additional securities or additional classes of securities pursuant to Rule 413(b) under the Securities Act, check the following box.  ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule 12b-2 of the Exchange Act.:

Large accelerated filer	x		Accelerated filer	¨
Non-accelerated filer	¨		Smaller reporting company	¨
			Emerging growth company	¨

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act.  ¨

DEREGISTRATION OF SECURITIES

Masimo Corporation, a Delaware corporation (the “Registrant”), is filing this post-effective amendment (the “Post-Effective Amendment”) to the Registration Statement on Form S-3 (Registration No. 333-285240) (the “Registration Statement”) filed with the Securities and Exchange Commission (the “SEC”) on February 25, 2025, to deregister all securities registered pursuant to the Registration Statement that remain unsold as of the date of this Post-Effective Amendment.

On June 10, 2026, pursuant to the terms of the Agreement and Plan of Merger (the “Merger Agreement”), dated as of February 16, 2026, by and among the Registrant, Danaher Corporation, a Delaware corporation (“Parent”), and Mobius Merger Sub, Inc., a Delaware corporation and a wholly owned subsidiary of Parent (“Merger Sub”), Merger Sub merged with and into the Registrant (the “Merger”), with the Registrant continuing as the surviving corporation and a wholly owned subsidiary of Parent.

As a result of the transactions contemplated by the Merger Agreement, all offerings of securities registered pursuant to the Registration Statement have been terminated. In accordance with undertakings made by the Registrant in the Registration Statement to remove from registration, by means of a post-effective amendment, any of the securities registered under the Registration Statement that remain unsold at the termination of the offering, the Registrant hereby removes from registration all of the securities registered but unsold under the Registration Statement as of the date hereof. The Registration Statement is hereby amended, as appropriate, to reflect the deregistration of such securities, and the Registrant hereby terminates the effectiveness of the Registration Statement.

The foregoing description of the Merger, the Merger Agreement and the transactions contemplated thereby does not purport to be complete and is subject to, and qualified in its entirety by the Merger Agreement, which is included as Exhibit 2.1 in the Registrant’s Form 8-K filed with the SEC on February 17, 2026.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, as amended (the “Securities Act”) the Registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-8 and has duly caused this Post-Effective Amendment to the Registration Statements to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Irvine, State of California, on June 10, 2026.

	MASIMO CORPORATION
	By:	/s/ Micah Young
		Name:	Micah Young
		Title:	EVP, Chief Financial Officer

No other person is required to sign this Post-Effective Amendment in reliance upon Rule 478 under the Securities Act of 1933, as amended.

FAQ

What did Masimo (MASI) do in this post-effective amendment?

Masimo removed from registration all unsold securities under Registration No. 333-285240. The amendment states the offerings were terminated following the merger consummated on June 10, 2026 pursuant to the Merger Agreement dated February 16, 2026.

Why did MASI terminate the Form S-3 registration?

The registration was terminated because Masimo became a wholly owned subsidiary of Danaher after the merger closing. The amendment cites the Merger Agreement and states all offerings under the registration were terminated and removed from registration.

Does the amendment disclose any offering size or proceeds for MASI?

No specific offering size, price range or proceeds are disclosed in the amendment. The document only states that unsold securities registered under Registration No. 333-285240 were removed and the registration terminated.

Where can I find the Merger Agreement referenced by MASI?

The amendment refers to the Merger Agreement dated February 16, 2026, which is included as Exhibit 2.1 to Masimo’s Form 8-K filed with the SEC on February 17, 2026. That exhibit contains the full agreement terms.

Will the deregistration affect future securities offerings by the combined company?

This amendment ends effectiveness of the specified Form S-3 registration. Any future public offerings by the combined company would require a new or different effective registration statement or reliance on another applicable registration mechanism.