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. 13)

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. 13 (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”), the Notice of Guaranteed Delivery (the “Notice of Guaranteed Delivery”), and the Supplement to the Offer to Purchase (the “Supplement to the Offer”), 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”).

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:

Items 1 through 9 and Item 11

1. The Offer to Purchase, the Supplement to the Offer and Items 1, 4 and 11 of the Schedule TO are hereby amended and supplemented by adding the following text thereto:

“On December 24, 2021, the Offeror announced an extension of the Expiration Date of the Offer until 12:00 midnight, New York City time, on Wednesday, January 26, 2022, unless the Offer is extended (such date and time, as it may be extended, the “Expiration Date”) or earlier terminated in the event that a condition to the Offer becomes incapable of being satisfied. The Offer was previously scheduled to expire at 12:00 midnight, New York City time, on December 27, 2021.

The Depositary has advised the Offeror that, as of 5:00 p.m., New York City time, on December 23, 2021, the last business day prior to the announcement of the extension of the Offer, approximately 8,670,967 Shares have been validly tendered pursuant to the Offer and not properly withdrawn, representing approximately 14.36% of the outstanding Shares. Of the Shares so tendered, none were tendered pursuant to guaranteed delivery procedures.

The full text of the press release announcing the extension of the Offer is attached hereto as Exhibit (a)(1)(W) and is incorporated herein by reference.”

2. The Offer to Purchase, the Supplement to the Offer and Items 1 through 9 and Item 11 of the Schedule TO, to the extent such items incorporate by reference the information contained in the Offer to Purchase, are hereby amended and supplemented as set forth below:

All descriptions and references in respect of the Expiration Date in the Offer to Purchase (Exhibit (a)(1)(A)), Letter of Transmittal (Exhibit (a)(1)(B)), Notice of Guaranteed Delivery (Exhibit (a)(1)(C)), Letter to Brokers, Dealers, Commercial Banks, Trust Companies and Other Nominees (Exhibit (a)(1)(D)), Letter to Clients for Use by Brokers, Dealers, Commercial Banks, Trust Companies and Other Nominees (Exhibit (a)(1)(E)), and the Supplement to the Offer to Purchase (Exhibit (a)(1)(T)) are hereby amended to reflect an extension of the Expiration Date from “12:00 midnight, New York City time, on December 27, 2021,” to “12:00 midnight, New York City time, on Wednesday, January 26, 2022.”

3. The information set forth in Section 18 of the Offer to Purchase, entitled “Legal Proceedings,” the Supplement to the Offer and Items 1 through 9 and Item 11 of the Schedule TO, to the extent such items incorporate by reference the information contained in the Offer to Purchase, are hereby amended and supplemented as set forth below:

“On December 21, 2021, the Court of Chancery of the State of Delaware held a hearing on Icahn Partners LP and Icahn Partners Master Fund LP’s (collectively, “Plaintiffs”) November 29, 2021 Motion for Temporary Restraining Order (the “Motion”). The Motion sought an order enjoining defendants John P. Hester, Michael J. Melarkey, Robert L. Boughner, Jose A. Cardenas, Stephen C. Comer, Jane Lewis-Raymond, Anne L. Mariucci, A. Randall Thoman, Thomas A. Thomas, Leslie T. Thornton, and Southwest Gas Holdings, Inc. (the “Company”) (collectively, “Defendants”) from (i) selling the Company’s stock to parties Defendants know or reasonably should know are likely to support the incumbent directors of Southwest Gas Holdings in the upcoming election and/or (ii) selling the Company’s stock to anyone at a price that is below $75 per share or such other higher price as Plaintiffs or their affiliates may offer. In the alternative, Plaintiffs requested an order requiring Defendants to provide Plaintiffs reasonable notice before they engage in any such sale so that Plaintiffs could take appropriate actions, including but not limited to seeking a preliminary injunction. At the conclusion of the hearing, the Court issued a ruling from the bench denying the Motion.”

Item 12. Exhibits.

Item 12 of the Schedule TO is hereby amended and supplemented by adding the following exhibit thereto:

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.

Date: December 27, 2021

Exhibit (a)(1)(W)

Icahn Enterprises Announces Extension of Southwest Gas Tender Offer

Sunny Isles Beach, Florida – December 24, 2021 – IEP Utility Holdings LLC, an affiliate of Icahn Enterprises L.P. (the “Offeror”), announced that it has extended the expiration date of its tender offer 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”), until 12:00 midnight, New York City time, on Wednesday, January 26, 2022, unless further extended or earlier terminated in the event that a condition to the Offer becomes incapable of being satisfied.

The Offer continues to be subject to the remaining conditions set forth in Section 14 — “Conditions of the Offer” of the Offer to Purchase. Complete terms and conditions of the tender offer can be found in the Offer to Purchase, the Letter of Transmittal, the Notice of Guaranteed Delivery, the Supplement to the Offer to Purchase, and certain other materials contained in the Offeror’s tender offer statement on Schedule TO originally filed with the U.S. Securities and Exchange Commission (“SEC”) on October 27, 2021, as amended and as may be further amended from time to time, and are available at www.sec.gov. Except as described in this press release, the terms of the tender offer remain the same as set forth in the Offer to Purchase, the Letter of Transmittal, the Notice of Guaranteed Delivery, and the Supplement to the Offer to Purchase, in each case, as amended.

Continental Stock Transfer & Trust Company, the depositary for the tender offer, has advised the Offeror that, as of 5:00 p.m., New York City time, on December 23, 2021, a total of approximately 8,670,967 Shares had been validly tendered and not properly withdrawn. Stockholders who have previously validly tendered and not withdrawn their shares do not need to re-tender their shares or take any other action in response to this extension.

Copies of the Offer to Purchase, the related Letter of Transmittal and other materials related to the tender offer may be obtained for free from the information agent, Harkins Kovler, LLC, at (800) 326-5997 (U.S. banks and brokerage firms, please call (212) 468-5380). The depositary for the tender offer is Continental Stock Transfer & Trust Company.

*****

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 DECEMBER 15, 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, AN AFFILIATE OF ICAHN ENTERPRISES, FILED A TENDER OFFER STATEMENT AND RELATED EXHIBITS WITH THE SEC ON OCTOBER 27, 2021. SOUTHWEST GAS FILED A SOLICITATION/ RECOMMENDATION STATEMENT WITH RESPECT TO THE TENDER OFFER WITH THE SEC ON NOVEMBER 9, 2021. STOCKHOLDERS OF SOUTHWEST GAS ARE STRONGLY ADVISED TO READ THE TENDER OFFER STATEMENT (INCLUDING THE RELATED EXHIBITS) AND THE SOLICITATION/RECOMMENDATION STATEMENT, 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 WITH THE SEC WILL BE MADE AVAILABLE TO ALL STOCKHOLDERS OF SOUTHWEST GAS FREE OF CHARGE UPON REQUEST TO THE INFORMATION AGENT FOR THE TENDER OFFER. THE INFORMATION AGENT FOR THE TENDER OFFER IS HARKINS KOVLER, LLC, 3 COLUMBUS CIRCLE, 15TH FLOOR, NEW YORK, NY 10019, TOLL-FREE TELEPHONE: +1 (800) 326-5997, EMAIL: SWX@HARKINSKOVLER.COM.

Other Important Disclosure Information

SPECIAL NOTE REGARDING THIS PRESS RELEASE

THIS PRESS RELEASE 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 PRESS RELEASE. 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 PRESS RELEASE OR PROVIDING ANY NOTICE WHATSOEVER OF ANY SUCH CHANGES (EXCEPT AS OTHERWISE REQUIRED BY LAW).

FORWARD-LOOKING STATEMENTS:

Certain statements contained in this press release 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.

Important factors that could cause actual results to differ materially from the expectations set forth in this press release 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.

Contacts:

Information Agent

Harkins Kovler, LLC

Peter Harkins / Jordan Kovler

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

pharkins@harkinskovler.com / jkovler@harkinskovler.com