0001692115-26-000102 | 11-K | XBRL Viewer | Southwest GAS Holdings INC

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The entire disclosure for fair value of investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), including, but not limited to, fair value measured at net asset value per share as practical expedient (NAV).

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Federal Income Taxes	12 Months Ended
Dec. 31, 2025
EBP 004
EBP, Tax Status [Line Items]
Federal Income Taxes	Note 5 - Federal Income Taxes In August 2016, the Company received a favorable determination letter from the IRS stating that the Plan, amended and restated effective January 1, 2015, qualifies for deferred tax treatment of contributions under Section 401(k) of the IRC. In 2015, the IRS announced that it was discontinuing its requirement that individually designed plans seeking approval be reviewed for new determination letters every five years and it will no longer review these plans except on adoption and termination. Management noted that the Plan has been amended, resulting in no significant changes, subsequent to receipt of its latest determination letter. U.S. GAAP requires Plan management to evaluate tax positions taken by the Plan. Management evaluated the Plan's tax positions and concluded that the Plan has maintained its tax-exempt status and has taken no uncertain tax positions that require recognition or disclosure in the financial statements. The Plan is subject to routine audits by taxing jurisdictions; however, there are currently no audits in progress for any tax periods.

Subsequent Events	12 Months Ended
Dec. 31, 2025
EBP 004
EBP, Subsequent Event [Line Items]
Subsequent Events	Note 7 - Subsequent Events Management of the Plan monitors events occurring after the Statements of Net Assets Available for Benefits date and through the issuance of the financial statements to determine the impacts, if any, of events on the financial statements to be issued or disclosures to be made, and has reflected them where appropriate.

Description of the Plan - Schedule of Vesting Percentages of Employer Contributions (Details) - EBP 004	12 Months Ended
Dec. 31, 2025
One but less than two
EBP, Description of Plan [Line Items]
Vested percentage	20.00%
Two but less than three
EBP, Description of Plan [Line Items]
Vested percentage	40.00%
Three but less than four
EBP, Description of Plan [Line Items]
Vested percentage	60.00%
Four but less than five
EBP, Description of Plan [Line Items]
Vested percentage	80.00%
Five and over
EBP, Description of Plan [Line Items]
Vested percentage	100.00%

Description of the Plan - Narrative (Details)	12 Months Ended
Description of the Plan - Narrative (Details)	Dec. 31, 2025 USD ($) year	Dec. 31, 2024 USD ($)
EBP, Description of Plan [Line Items]
Participant loans, maximum borrowing term	5 years
EBP 004
EBP, Description of Plan [Line Items]
Automatic plan enrollment, requisite period	30 days
Participant contribution, minimum annual compensation to total compensation	2.00%
Participant contribution, maximum annual compensation to total compensation	75.00%
Employer contribution maximum vesting age \| year	65
Forfeited nonvested account, reallocated to participant	$ 447,000	$ 293,000
Participant loans, basis spread on variable rate	2.00%
Individual retirement account, triggering amount	$ 5,000
Involuntary cash-out limit	$ 1,000
Period to request payment by beneficiary in event of death of participant	5 years
Loan origination and maintenance fees paid by participant	$ 297,582
EBP 004 \| Minimum
EBP, Description of Plan [Line Items]
Participant loans, interest rate	5.25%
EBP 004 \| Maximum
EBP, Description of Plan [Line Items]
Participant loans, interest rate	10.50%
EBP 004 \| EBP, Retirement Age On Or After January 1, 2020
EBP, Description of Plan [Line Items]
Retirement age \| year	72
EBP 004 \| EBP, Retirement Age Prior To January 1, 2020
EBP, Description of Plan [Line Items]
Retirement age \| year	70.5
EBP 004 \| EBP, Hired Prior To January 1, 2022
EBP, Description of Plan [Line Items]
Employer contribution, matching percentage	50.00%
Employer contribution, participant compensation matched, percentage	3.50%
EBP 004 \| EBP, Hired On Or After January 1, 2022
EBP, Description of Plan [Line Items]
Employer contribution, participant compensation matched, percentage	7.00%
EBP 004 \| EBP, Hired On Or After January 1, 2022 \| EBP, Non-Elective Contribution
EBP, Description of Plan [Line Items]
Employer contribution, matching percentage	3.00%
EBP 004 \| EBP, Hired On Or After January 1, 2022 \| EBP, Employer Matching And Non-Elective Contribution
EBP, Description of Plan [Line Items]
Employer contribution, matching percentage	10.00%

Related-Party and Party-In-Interest Transactions - Schedule of Investments Held by Party-In-Interest (Details) - EBP 004 - USD ($)	Dec. 31, 2025	Dec. 31, 2024
EBP, Related Party and Party-in-Interest Transactions [Line Items]
Investments held by parties-in-interest	$ 683,562,499	$ 590,712,929
EBP, Employer, Common Stock And Fidelity Management Trust Company
EBP, Related Party and Party-in-Interest Transactions [Line Items]
Investments held by parties-in-interest	551,631,674	468,843,415
EBP, Fidelity Management Trust Company
EBP, Related Party and Party-in-Interest Transactions [Line Items]
Investments held by parties-in-interest	491,306,477	413,498,661
Company Common Stock
EBP, Related Party and Party-in-Interest Transactions [Line Items]
Investments held by parties-in-interest	$ 60,325,197	$ 55,344,754

Fair value of investment, excluding plan interest in master trust, held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Includes, but is not limited to, derivative, investment measured at net asset value per share as practical expedient, and insurance contract not meeting fully-benefit responsive investment criteria.

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Fair Value Measurements - Schedule of Plan Assets Accounted at Fair Value (Details) - EBP 004 - USD ($)	Dec. 31, 2025	Dec. 31, 2024
EBP, Investment, Fair Value and NAV [Line Items]
Investments at fair value	$ 683,562,499	$ 590,712,929
Company Common Stock
EBP, Investment, Fair Value and NAV [Line Items]
Investments at fair value	60,325,197	55,344,754
Fair Value, Inputs, Level 1
EBP, Investment, Fair Value and NAV [Line Items]
Investments at fair value	243,678,249	214,770,000
Fair Value, Inputs, Level 1 \| Company Common Stock
EBP, Investment, Fair Value and NAV [Line Items]
Investments at fair value	60,325,197	55,344,754
Fair Value, Inputs, Level 1 \| Temporary cash investments
EBP, Investment, Fair Value and NAV [Line Items]
Investments at fair value	6,449	5,781
Fair Value, Inputs, Level 1 \| Mutual Funds
EBP, Investment, Fair Value and NAV [Line Items]
Investments at fair value	183,346,603	159,419,465
Fair Value Measured at Net Asset Value Per Share \| Common Collective Trusts
EBP, Investment, Fair Value and NAV [Line Items]
Investments at fair value	$ 439,884,250	$ 375,942,929

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Summary of Accounting Policies (Policies) - EBP 004	12 Months Ended
Summary of Accounting Policies (Policies) - EBP 004	Dec. 31, 2025
EBP, Accounting Policy [Line Items]
Basis of Accounting	Basis of Accounting The financial statements of the Plan are prepared in conformity with generally accepted accounting principles in the United States (“U.S. GAAP”).
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of changes in net assets during the reporting period. Actual results could materially differ from those estimates.
Investment Valuation and Income Recognition	Investment Valuation and Income Recognition Investments are reported at fair value. Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. Common Collective Trusts are measured using their net asset value (“NAV”) of shares held by the Plan at year-end. See Note 6 - Fair Value Measurements. Purchases and sales of securities are generally valued on an end-of-trade-date pricing basis with the exception of exchanges in and out of the Southwest Gas Stock Fund. When exchanging into Company Common Stock, the stock purchase will be processed on the trade date in real-time pricing. When exchanging out of Company Common Stock, the stock sale will be processed on the trade date in real-time pricing, and the exchange into another investment option will be processed three business days after the trade date (in accordance with normal securities settlement practice). Exchanges in and out of Company Common Stock are generally reflected in participant accounts the day following the trade date. Other purchase and sale transactions, such as contributions, loans, and withdrawals involving Company Common Stock, are not subject to real-time trading. Dividends are recorded on the ex-dividend date.
Notes Receivable from Participants	Notes Receivable from Participants Notes receivable from participants (participant loans) are measured at their unpaid principal balance plus any accrued but unpaid interest. No allowance for credit losses has been recorded at December 31, 2025 or 2024. If a participant ceases to make a note repayment and the Plan administrator deems the note to be a distribution, the note receivable balance is reduced and a benefit payment is recorded.
Contributions Receivable	Contributions Receivable Contributions receivable consist of employer and/or employee contributions, when applicable, made but not yet received by the Plan.
Risks and Uncertainties	Risks and Uncertainties Investment securities, in general, are exposed to various risks, such as interest rate, credit, and overall market volatility risks as well as changes in prevailing market and interest rates, increases in defaults and credit rating downgrades. Due to the level of risk associated with certain investment securities and the amount invested in Company Common Stock, it is reasonably possible that changes in the values of investment securities will occur in the near term and such changes could materially affect the amounts reported in the Statements of Net Assets Available for Benefits.
Payment of Benefits	Payment of Benefits Benefits are recorded when paid.

Disclosure of accounting policy for use of estimate in preparation of financial statement of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References + Details

Statements of Net Assets Available for Benefits - EBP 004 - USD ($)	Dec. 31, 2025	Dec. 31, 2024
Assets:
Investments at fair value	$ 683,562,499	$ 590,712,929
Notes receivable from participants	9,321,006	9,106,084
Contribution receivable from employer	177,571	111,731
Total assets	693,061,076	599,930,744
Net assets available for benefits	$ 693,061,076	$ 599,930,744

Amount of asset less liability available to pay benefit of participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), including, but not limited to, aggregation of participants' individual account balances.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 325
-Name Accounting Standards Codification
-Section 45
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477509/962-325-45-8

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
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-Paragraph 1
-Subparagraph (b)(3)
-Publisher FASB
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Reference 3: http://www.xbrl.org/2003/role/exampleRef
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Reference 4: http://www.xbrl.org/2003/role/exampleRef
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Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-05(a)(Schedule II))
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org/1943274/2147477063/962-205-45-2

EBP, Description of Plan [Line Items]

Description of the Plan

12 Months Ended

Dec. 31, 2025

EBP 004

Description of the Plan

Note 1 - Description of the Plan

The following description of the Southwest Gas Corporation Employees’ Investment Plan (the “Plan”), as amended, provides general information. Participants should refer to the Plan document for a more complete description of the Plan’s provisions.

General

The Plan is a voluntary defined contribution plan covering all employees of Southwest Gas Corporation (the “Company”). However, references within these disclosures to “Company Stock” or “Company Common Stock” relate to stock of the Company's parent entity, Southwest Gas Holdings, Inc., the ticker symbol for which is “SWX.” The Plan is subject to the provisions of the Employee Retirement Income Security Act of 1974 (“ERISA”). Its assets invested in Company stock (consisting of (i) Company matching contributions and (ii) participant deferrals) are designated as an Employee Stock Ownership Plan (“ESOP”). New employees are automatically enrolled in the Plan after 30 days unless they elect not to participate. The Plan is for the benefit of employees of the Company.

The ESOP invests primarily in qualifying employer securities. The non-ESOP portion of the Plan is a profit-sharing plan that is qualified under Internal Revenue Code (“IRC”) Sections 401(a) and 401(k). The ESOP portion of the Plan is a stock bonus plan and an employee stock ownership plan that is qualified under IRC Sections 401(a) and 4975(e)(7) and described in ERISA Section 407(d)(6). The profit-sharing plan and the ESOP together compose a single plan under Treasury Regulation Section 1.414(1)-1(b)(1). The Plan satisfies the requirements of ERISA and the trust fund maintained under the Plan is tax-exempt under IRC Section 501(a).

In January 2022, the Plan was amended with respect to employees hired or re-hired on or after January 1, 2022, who will participate in enhanced benefits under the Plan rather than in a separate defined benefit retirement plan. Enhanced benefits under the Plan are discussed below. The change is not applicable to employees hired on or before December 31, 2021.

Contributions

Participants may contribute from 2% to 75% of their annual base wages. However, contributions may not exceed amounts promulgated by the IRC. For participants hired prior to January 1, 2022, the Company contributes to the Plan an amount equal to 50% of a participant’s contribution. The Company’s maximum contribution in this case is 3.5% of a participant’s annual base compensation as defined in the Plan document. For participants hired on or after January 1, 2022, the Company makes a 3% non-elective contribution (effective upon hire), plus a matching contribution (dollar-for-dollar) for every dollar saved up to 7% of eligible compensation, bringing the maximum Company contribution up to 10% as defined in the Plan. Deferral percentages elected by participants are also applied to overtime earnings; however, deferral of such earnings is not matched by the Company. Roth contributions are eligible for Company matching contributions.

The SECURE 2.0 Act of 2022 (“SECURE 2.0”), enacted in 2023, includes provisions that affect tax‑qualified retirement plans. Certain provisions of SECURE 2.0 were effective in 2023, whereas other provisions are effective for 2024 or later years. Furthermore, many provisions are optional, including some that the Plan may adopt, while others it will not adopt.

Under current law, the Plan may permit qualified birth or adoption distributions of up to $5,000, as described in Code Section 72(t)(2)(H), and may permit qualified disaster recovery distributions of up to $22,000 for individuals affected by federally declared disasters, in each case subject to applicable Internal Revenue Service limitations and requirements.

Under current law, employees aged 50 or older are permitted to make catch-up contributions of $7,500 in excess of otherwise applicable annual limits. Starting in 2025, SECURE 2.0 allows for an additional “tier” of catch-up contributions for individuals who are ages 60 to 63. Such individuals will have a limit for 2025 and 2026 of $11,250, which is the greater of $10,000 or 150% of the regular catch-up amount, whichever is greater for the applicable year. The increased amounts are indexed for inflation after 2025.

As part of SECURE 2.0, beginning in 2026, catch-up contributions made by participants age 50 or older whose prior-year wages exceed the applicable IRS threshold must be made on a Roth basis. The SECURE 2.0 Act originally established the threshold at $145,000 per year (as indexed). In Notice 2023-62, the Internal Revenue Service (“IRS”) provided an administrative transition period delaying this requirement until January 1, 2026. Subsequently, in Notice 2025-67, the IRS increased the applicable wage threshold for 2026 to $150,000 per year.

Participants’ Accounts

Each participant account is credited with the participant’s contribution and amounts contributed by the Company. Participant and Company contributions are invested in the various funds according to the direction of the participant.

Vesting

Participants are immediately vested in their voluntary contributions plus actual earnings thereon. Vesting in the contributions made by the Company and in the earnings thereon is based on years of continuous service. Participants are fully vested in dividends paid in the Southwest Gas Stock Fund (“Southwest Gas Stock Fund”) without regard to whether the participant is vested in the Company Common Stock with respect to which the dividend is paid. The following table shows the vesting schedule of Company contributions and the earnings thereon (other than dividends on the Southwest Gas Stock Fund).


						Vested
Years of Service						Percentage
One but less than two						20
Two but less than three						40
Three but less than four						60
Four but less than five						80
Five and over						100

In the event of death, attainment of age 65, total disability of a participant, or Plan termination, Company contributions become fully vested irrespective of the years of service. Forfeitures as a result of a participant’s termination prior to vesting, that are not utilized to restore prior benefits or to pay benefits to previously unlocated participants and beneficiaries, are reallocated to the remaining participants on a quarterly basis based on the employer contribution ratio. For the years ended December 31, 2025 and 2024, forfeitures of non-vested accounts reallocated to participants were approximately $447,000 and $293,000, respectively.

Notes Receivable from Participants (Participant Loans)

The Plan provides that participants may borrow against the contribution and rollover balances in their accounts, subject to certain limitations specified in the Plan. Funds for loans are obtained through the liquidation of participants’ investment accounts. Payments on the loans include interest at a rate that approximates the prime rate, plus 2%. At December 31, 2025, all outstanding loans had annual interest rates ranging from 5.25% to 10.50%, maturing through 2030. Principal and interest payments on participant loans are credited to participant contribution and rollover accounts in the same ratio as ongoing investment elections. The maximum repayment period for participant loans is five years.

Payment of Benefits

If a participant terminates employment with the Company as a result of retirement, death, or permanent and total disability, such participant, or designated beneficiary in the case of participant death, will be entitled to receive an amount equal to the value of their account as soon as practicable following termination of employment. Distributions from the Southwest Gas Stock Fund will be made in Company Common Stock plus cash in lieu of fractional shares. A participant may apply to the Company’s Benefits Committee (the “Committee”) to request a single lump sum payment in cash for the value of Company Common Stock otherwise distributable to the participant. Lump sum distributions from other funds will be paid in cash.

Under existing provisions of the Plan, or those applicable from SECURE 2.0, distributions under the Plan will begin as soon as practicable, but no later than April 1 following the end of the Plan year in which the participant attains age 72 (70-1/2 if you reach age 70-1/2 before January 1, 2020) or terminates employment (if occurring after age 72). SECURE 2.0 increases the required minimum distribution age to 73 (for individuals born between 1951 and 1959) and age 75 (for individuals who attain age 74 after December 31, 2032). If the participant’s vested account balance is less than $5,000, the participant may request a lump-sum distribution or direct that the amount be rolled over into an Individual Retirement Account (“IRA”). If no election is made and the balance does not exceed $1,000, it will be distributed to the participant. If no election is made and the balance is greater than $1,000 but does not exceed $5,000, it will be rolled over to an IRA, designated by the Committee, for the benefit of the participant. If the participant’s vested account balance is greater than $5,000, the participant may remain in the Plan, receive a lump-

sum distribution, or roll over the account into an IRA in 2024 or a later Plan year. SECURE 2.0 provides that the Plan may be amended to increase the $5,000 limit to $7,000. In this case, a participant who is terminated and does not elect to take a distribution will continue to receive their share of investment income on all vested portions of their account until electing to receive distributions from the Plan. SECURE 2.0 eliminates the pre-death distribution requirement for Roth accounts in employer plans for taxable years beginning after December 31, 2023. However, this change does not apply to distributions that are required with respect to years beginning before January 1, 2024, but are permitted to be paid on or after such date. Beneficiaries of a participant have no more than five years after the participant’s death to request payment.

A participant or surviving spouse, if the designated beneficiary, is permitted to make partial withdrawals as long as minimum distribution requirements are met.

Plan Expenses

Plan-related expenses and any other costs of administering the Plan will be paid with funds from the Plan unless paid by the Company at its discretion. The Company paid all administrative Plan expenses, except loan origination and maintenance fees, during 2025. Loan origination and maintenance fees paid by Plan participants for the year ended December 31, 2025 were $297,582.

Other Income

The Plan participates in Fidelity’s revenue credit program, which allows the Plan sponsor to apply credits received to pay for ERISA qualified expenses and/or allocate credits to participants on a pro rata basis. The pro rata allocation is based on the ratio of each participant’s average daily balance in a fund during the quarter to the total average daily balances for all participants in such fund during the quarter. These revenue credits qualify as party-in-interest transactions for which a statutory exemption exists.

Plan Administration

The Committee is the administrator for all activities of the Plan. Fidelity Management Trust Company acts as the Trustee and Fidelity Investments Institutional Operations Company performs all recordkeeping of the Plan.

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2025

EBP 004

EBP, Investment, Fair Value and NAV [Line Items]

Schedule of Plan Assets Accounted at Fair Value

The following table presents information about the Plan’s assets measured at fair value.


	December 31,
	2025		2024
Assets values:
Level 1 - Quoted prices in active markets for identical financial assets
Mutual Funds	$	183,346,603	$	159,419,465
Company Common Stock	60,325,197		55,344,754
Temporary cash investments	6,449		5,781
Total Level 1 assets	243,678,249		214,770,000
Assets measured in NAV:
Common Collective Trusts	439,884,250		375,942,929
Total assets at fair value	$	683,562,499	$	590,712,929

The following table sets forth a summary of the Plan’s investments for which the fair value has been estimated using the NAV of the investments.

December 31,

Unfunded Commitment and Other Redemption Restrictions

Redemption Frequency

Redemption Notice Period

2025

2024

Fidelity Contrafund Pool Class A

143,657,806

128,083,767

None

Daily

1-day

Fidelity Freedom 2010 Commingled Pool Class D

3,035,018

1,246,650

None

Daily

1-day

Fidelity Freedom 2015 Commingled Pool Class D

4,574,356

4,002,932

None

Daily

1-day

Fidelity Freedom 2020 Commingled Pool Class D

14,432,866

13,320,326

None

Daily

1-day

Fidelity Freedom 2025 Commingled Pool Class D

22,124,940

25,416,164

None

Daily

1-day

Fidelity Freedom 2030 Commingled Pool Class D

37,062,094

33,161,952

None

Daily

1-day

Fidelity Freedom 2035 Commingled Pool Class D

27,356,002

21,411,336

None

Daily

1-day

Fidelity Freedom 2040 Commingled Pool Class D

38,257,480

30,480,439

None

Daily

1-day

Fidelity Freedom 2045 Commingled Pool Class D

32,163,082

24,075,501

None

Daily

1-day

Fidelity Freedom 2050 Commingled Pool Class D

26,830,501

19,768,419

None

Daily

1-day

Fidelity Freedom 2055 Commingled Pool Class D

20,094,378

14,439,162

None

Daily

1-day

Fidelity Freedom 2060 Commingled Pool Class D

11,476,100

7,800,310

None

Daily

1-day

Fidelity Freedom 2065 Commingled Pool Class D

5,068,131

2,728,504

None

Daily

1-day

Fidelity Freedom Retirement Commingled Pool Class D

3,225,182

3,370,539

None

Daily

1-day

FIAM Core Plus Commingled Pool Class F

23,197,709

19,011,401

None

Daily

1-day

T. Rowe Price Stable Value Common Trust Fund A

27,328,605

27,625,527

None

Daily

1-day

439,884,250

375,942,929

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Tabular disclosure of fair value of investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), including, but not limited to, fair value measured at net asset value per share as practical expedient (NAV).