UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE TO

Tender Offer Statement under Section 14(d)(1) or 13(e)(1)

of the Securities Exchange Act of 1934

(Amendment No. 4)

SOUTHWEST GAS HOLDINGS, INC.

(Name of Subject Company)

IEP UTILITY HOLDINGS LLC

ICAHN ENTERPRISES HOLDINGS L.P.

ICAHN ENTERPRISES L.P.

ICAHN ENTERPRISES G.P. INC.

BECKTON CORP.

CARL C. ICAHN

(Names of Filing Persons) (Offerors))

Common Stock, par value $1.00 per share

(Title of Class of Securities)

844895102

(CUSIP Number of Class of Securities)

Jesse Lynn, Esq.

Icahn Enterprises L.P.

16690 Collins Avenue, Suite PH-1

Sunny Isles Beach, FL 33160

(305) 422-4100

(Name, Address, and Telephone Number of Person Authorized to Receive Notices and Communications on Behalf of Filing Persons)

CALCULATION OF FILING FEE

Check the appropriate boxes below to designate any transactions to which the statement relates:

Check the following box if the filing is a final amendment reporting the results of the tender offer. ☐

If applicable, check the appropriate box(es) below to designate the appropriate rule provision(s) relied upon:

This Amendment No. 4 (this “Amendment”) amends and supplements the Tender Offer Statement on Schedule TO, originally filed with the Securities and Exchange Commission (the “SEC”) on October 27, 2021 (as hereby amended and supplemented and together with any subsequent amendments and supplements thereto, this “Schedule TO”), which relates to the tender offer by IEP Utility Holdings LLC, a Delaware limited liability company (the “Offeror”), to purchase any and all of the issued and outstanding shares of the common stock, par value $1.00 per share (the “Common Stock”), of Southwest Gas Holdings, Inc., a Delaware corporation (the “Company” or “Southwest Gas”), including the associated rights issued pursuant to the Rights Agreement, dated October 10, 2021 (as it may be amended from time to time, the “Rights Agreement”), between the Company and Equiniti Trust Company, as rights agent, that are issued and outstanding (the “Rights” and, together with the Common Stock, the “Shares”), for $75.00 per Share in cash, without interest, less any applicable withholding taxes (the “Offer Price”), upon the terms and subject to the conditions set forth in the Offer to Purchase, dated October 27, 2021 (the “Offer to Purchase”), the related letter of transmittal (the “Letter of Transmittal”), and the Notice of Guaranteed Delivery (the “Notice of Guaranteed Delivery”, which, together with the Offer to Purchase, the Letter of Transmittal and the other related materials, as each may be amended or supplemented from time to time, constitutes the “Offer”), copies of which were previously filed with the Schedule TO.

This Amendment is being filed to amend and supplement the Schedule TO. Except as amended hereby to the extent specifically provided herein, all terms of the Offer and all other disclosures set forth in the Schedule TO and the Exhibits thereto remain unchanged and are hereby expressly incorporated into this Amendment by reference. Capitalized terms used and not otherwise defined in this Amendment shall have the meanings assigned to such terms in the Schedule TO and the Offer to Purchase.

The Schedule TO is hereby amended and supplemented as follows:

Item 12. Exhibits.

Item 12 of the Schedule TO is hereby amended and supplemented by adding Exhibit (a)(1)(M) thereto:

* Previously filed

SIGNATURES

After due inquiry and to the best knowledge and belief of the undersigned, each of the undersigned certify that the information set forth in this statement is true, complete and correct.

Exhibit (a)(1)(M)

Carl C. Icahn Issues Open Letter to

Stockholders of Southwest Gas

Sunny Isles Beach, Florida, November 9, 2021 — Today, Carl C. Icahn released the following open letter to the stockholders of Southwest Gas Holdings, Inc. (NYSE: SWX).

Investor Contacts:

Harkins Kovler, LLC

Peter Harkins / Jordan Kovler

(212) 468-5390 / (212) 468-5384

pharkins@harkinskovler.com / jkovler@harkinskovler.com

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CARL C. ICAHN

16690 Collins Avenue, Suite PH-1

Sunny Isles Beach, FL 33160

November 9, 2021

To ALL Stockholders of SWX:

The statement issued today by the SWX board in response to our tender offer is almost inexplicable and frankly the height of hypocrisy. At the same time that they’re telling stockholders their stock is worth more than our $75 offer, they’re amazingly also saying they’ve determined to issue up to $1 billion of new stock, equivalent to almost 25% of the current market capitalization, in order to finance an ill-advised acquisition that will provide NO synergies and NO growth! That stock issuance would likely be at a valuation well below the currently depressed market price of $68. In other words, it’s fine for the board, in their infinite wisdom, to sell a block of SWX stock at somewhere below $68, but they’re advising YOU not to sell at $75. What are we missing?

It is patently obvious that if the SWX board truly believed our company was worth more than $75 per share, they wouldn’t be proposing to issue up to 25% of the company at bargain basement prices. Some might even call this gross negligence.

In addition, the board’s claim that our offer is “illusory” and “highly conditional” is equally disingenuous and we believe intentionally misleading. We have taken great pains to eliminate every “boilerplate” condition that appears in almost every tender offer. For example, our offer is NOT conditioned on us obtaining financing, and it is NOT conditioned on no “material adverse effect” having occurred. It is also not conditioned on us conducting any due diligence.

It is interesting that two of the “conditions” the SWX board has focused on in our tender offer are of their own making and solely within their control to eliminate! For example, our condition requiring elimination of the “poison pill,” which the board implemented after we arrived on the scene, could easily be eliminated if they would simply remove the pill. Additionally, our condition requiring waiver of the “dominant stockholder” provision contained in SWX’s charter is necessitated only by the board’s own actions and could easily be eliminated by the board. We believe it is self-evident that the only reason the board will not remove these impediments is to entrench their positions and protect their lucrative cash compensation.

We believe that if the board had any meaningful stock ownership in SWX (they collectively own well under 1% of the company!) they would be reacting very differently to our compelling offer. Ask yourself: Why won’t the SWX board let the SWX stockholders decide for themselves whether they wish to accept our offer?”

Sincerely yours,

Carl C. Icahn

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Additional Information and Where to Find It;

Participants in the Solicitation and Notice to Investors

SECURITY HOLDERS ARE ADVISED TO READ THE PROXY STATEMENT AND OTHER DOCUMENTS RELATED TO THE SOLICITATION OF PROXIES BY CARL C. ICAHN AND HIS AFFILIATES FROM THE STOCKHOLDERS OF SOUTHWEST GAS HOLDINGS, INC (“SOUTHWEST GAS”) FOR USE AT THE ANNUAL MEETING OF STOCKHOLDERS OF SOUTHWEST GAS WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION, INCLUDING INFORMATION RELATING TO THE PARTICIPANTS IN SUCH PROXY SOLICITATION. WHEN COMPLETED, A DEFINITIVE PROXY STATEMENT AND A FORM OF PROXY WILL BE MAILED TO STOCKHOLDERS OF SOUTHWEST GAS AND WILL ALSO BE AVAILABLE AT NO CHARGE AT THE SECURITIES AND EXCHANGE COMMISSION’S (“SEC”) WEBSITE AT HTTP://WWW.SEC.GOV. INFORMATION RELATING TO THE PARTICIPANTS IN SUCH PROXY SOLICITATION IS CONTAINED IN THE SCHEDULE 14A FILED BY CARL C. ICAHN AND HIS AFFILIATES WITH THE SECURITES AND EXCHANGE COMMISSION ON OCTOBER 5, 2021. EXCEPT AS OTHERWISE DISCLOSED IN THE SCHEDULE 14A, THE PARTICIPANTS HAVE NO INTEREST IN SOUTHWEST GAS.

THE SOLICITATION DISCUSSED HEREIN RELATES TO THE SOLICITATION OF PROXIES FOR USE AT THE 2022 ANNUAL MEETING OF STOCKHOLDERS OF SOUTHWEST GAS HOLDINGS.

THIS COMMUNICATION IS FOR INFORMATIONAL PURPOSES ONLY AND IS NOT A RECOMMENDATION, AN OFFER TO PURCHASE OR A SOLICITATION OF AN OFFER TO SELL SHARES. IEP UTILITY HOLDINGS LLC AND ICAHN ENTERPRISES HOLDINGS L.P., AFFILIATES OF ICAHN ENTERPRISES, FILED A TENDER OFFER STATEMENT AND RELATED EXHIBITS WITH THE SEC ON OCTOBER 27, 2021. SWX WILL FILE A SOLICITATION/ RECOMMENDATION STATEMENT WITH RESPECT TO THE TENDER OFFER WITH THE SEC. STOCKHOLDERS OF SWX ARE STRONGLY ADVISED TO READ THE TENDER OFFER STATEMENT (INCLUDING THE RELATED EXHIBITS) AND THE SOLICITATION/RECOMMENDATION STATEMENT, WHEN AVAILABLE, AS THEY MAY BE AMENDED FROM TIME TO TIME, BECAUSE THEY CONTAIN IMPORTANT INFORMATION THAT STOCKHOLDERS SHOULD CONSIDER BEFORE MAKING ANY DECISION REGARDING TENDERING THEIR SHARES. THE TENDER OFFER STATEMENT (INCLUDING THE RELATED EXHIBITS) AND THE SOLICITATION/RECOMMENDATION STATEMENT ARE AVAILABLE AT NO CHARGE ON THE SEC’S WEBSITE AT WWW.SEC.GOV. THE TENDER OFFER STATEMENT AND OTHER DOCUMENTS THAT ARE FILED BY IEP UTLITY HOLDINGS LLC AND ICAHN ENTERPRISES HOLDINGS L.P. WITH THE SEC WILL BE MADE AVAILABLE TO ALL STOCKHOLDERS OF SWX FREE OF CHARGE UPON REQUEST TO THE INFORMATION AGENT FOR THE TENDER OFFER. THE INFORMATION AGENT FOR THE TENDER OFFER WILL BE HARKINS KOVLER, LLC, 3 COLUMBUS CIRCLE, 15TH FLOOR, NEW YORK, NY 10019, TOLL-FREE TELEPHONE: +1 (800) 326-5997, EMAIL: SWX@HARKINSKOVLER.COM.

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Other Important Disclosure Information

SPECIAL NOTE REGARDING THIS LETTER:

THIS LETTER CONTAINS OUR CURRENT VIEWS ON THE VALUE OF SOUTHWEST GAS SECURITIES AND CERTAIN ACTIONS THAT SOUTHWEST GAS’ BOARD MAY TAKE TO ENHANCE THE VALUE OF ITS SECURITIES. OUR VIEWS ARE BASED ON OUR OWN ANALYSIS OF PUBLICLY AVAILABLE INFORMATION AND ASSUMPTIONS WE BELIEVE TO BE REASONABLE. THERE CAN BE NO ASSURANCE THAT THE INFORMATION WE CONSIDERED AND ANALYZED IS ACCURATE OR COMPLETE. SIMILARLY, THERE CAN BE NO ASSURANCE THAT OUR ASSUMPTIONS ARE CORRECT. SOUTHWEST GAS’ PERFORMANCE AND RESULTS MAY DIFFER MATERIALLY FROM OUR ASSUMPTIONS AND ANALYSIS.

WE HAVE NOT SOUGHT, NOR HAVE WE RECEIVED, PERMISSION FROM ANY THIRD-PARTY TO INCLUDE THEIR INFORMATION IN THIS LETTER. ANY SUCH INFORMATION SHOULD NOT BE VIEWED AS INDICATING THE SUPPORT OF SUCH THIRD PARTY FOR THE VIEWS EXPRESSED HEREIN.

OUR VIEWS AND OUR HOLDINGS COULD CHANGE AT ANY TIME. WE MAY SELL ANY OR ALL OF OUR HOLDINGS OR INCREASE OUR HOLDINGS BY PURCHASING ADDITIONAL SECURITIES. WE MAY TAKE ANY OF THESE OR OTHER ACTIONS REGARDING SOUTHWEST GAS WITHOUT UPDATING THIS LETTER OR PROVIDING ANY NOTICE WHATSOEVER OF ANY SUCH CHANGES (EXCEPT AS OTHERWISE REQUIRED BY LAW).

FORWARD-LOOKING STATEMENTS:

Certain statements contained in this letter are forward-looking statements including, but not limited to, statements that are predications of or indicate future events, trends, plans or objectives. Undue reliance should not be placed on such statements because, by their nature, they are subject to known and unknown risks and uncertainties. Forward-looking statements are not guarantees of future performance or activities and are subject to many risks and uncertainties. Due to such risks and uncertainties, actual events or results or actual performance may differ materially from those reflected or contemplated in such forward-looking statements. Forward-looking statements can be identified by the use of the future tense or other forward-looking words such as “believe,” “expect,” “anticipate,” “intend,” “plan,” “estimate,” “should,” “may,” “will,” “objective,” “projection,” “forecast,” “management believes,” “continue,” “strategy,” “position” or the negative of those terms or other variations of them or by comparable terminology.

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Important factors that could cause actual results to differ materially from the expectations set forth in this letter include, among other things, the factors identified in Southwest Gas’ public filings. Such forward-looking statements should therefore be construed in light of such factors, and we are under no obligation, and expressly disclaim any intention or obligation, to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise, except as required by law.

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