American Century group reports 5.1% AdvanSix (ASIX) stake in Schedule 13G

Rhea-AI Filing Summary

American Century Investment Management, Inc., together with American Century Companies, Inc. and the Stowers Institute for Medical Research, reports beneficial ownership of AdvanSix Inc. common stock. The group holds 1,363,346 shares, representing 5.1% of the outstanding common stock as of June 30, 2026.

The reporting persons have sole voting and sole dispositive power over the 1,363,346 shares, with no shared voting or dispositive power. Various investment company and institutional accounts advised by American Century Investment Management, Inc. have rights to dividends and sale proceeds, but no single client holds more than 5% of the class.

Key Figures

Beneficially owned shares: 1,363,346 shares Ownership percentage: 5.1% Sole voting power: 1,363,346 shares +1 more

4 metrics

Beneficially owned shares 1,363,346 shares AdvanSix common stock beneficially owned as of June 30, 2026

Ownership percentage 5.1% Percent of AdvanSix common stock class beneficially owned

Sole voting power 1,363,346 shares Shares over which the reporting persons have sole power to vote

Sole dispositive power 1,363,346 shares Shares over which the reporting persons have sole power to dispose

Key Terms

beneficial ownership, sole voting power, sole dispositive power, Schedule 13G, +1 more

5 terms

beneficial ownership financial

"the beneficial ownership of the securities which are the subject of this schedule"

Beneficial ownership means the person or entity that actually enjoys the benefits of owning shares or other assets — such as receiving dividends, voting rights, or price gains — even if the legal title is held in another name. For investors it matters because knowing who truly controls and profits from a company reveals who can influence decisions, exposes potential conflicts of interest or hidden concentration of power, and affects transparency and risk in the stock.

sole voting power financial

"5 | Sole Voting Power 1,363,346.00 6 | Shared Voting Power 0.00"

Sole voting power is the exclusive right to cast votes attached to a shareholder’s stock without needing approval from anyone else. Like holding the only remote control for a TV, it lets that holder decide corporate matters such as board members, mergers, and policy changes, making it important to investors because it concentrates control and can strongly influence a company’s strategy and the value of its shares.

sole dispositive power financial

"7 | Sole Dispositive Power 1,363,346.00 8 | Shared Dispositive Power 0.00"

Sole dispositive power is the exclusive legal authority to decide what happens to a security — for example, whether to sell, transfer, or retain shares — without needing anyone else’s permission. Investors care because it signals who truly controls the economic outcome of an investment: like holding the only key to a safe, the holder can realize gains or losses and may trigger regulatory reporting, insider rules, or influence over corporate ownership.

Schedule 13G regulatory

"beneficial ownership of the securities that are the subject of this schedule"

A Schedule 13G is a formal document that investors file with the government when they acquire a large ownership stake in a company, usually for investment purposes rather than control. It helps keep the public informed about who owns significant parts of a company's shares, which can influence how the company is managed and how investors make decisions. Filing this schedule is important for transparency and understanding the ownership landscape of publicly traded companies.

investment adviser financial

"American Century Investment Management, Inc. ("ACIM") serves as investment adviser"

An investment adviser is a person or firm that professionally manages money and gives recommendations about buying, selling, or holding investments. Like a financial coach or guide, they have a legal duty to act in a client's best financial interest, so their advice, fees and potential conflicts can directly affect returns and risk — making their role important for investors who want informed, accountable help with portfolios.

FAQ

What percentage of AdvanSix Inc. (ASIX) does American Century report owning?

American Century and related entities report beneficial ownership of 5.1% of AdvanSix Inc. common stock. This stake corresponds to 1,363,346 shares, held with sole voting and sole dispositive power over the reported securities.

How many AdvanSix (ASIX) shares are beneficially owned according to this Schedule 13G?

The filing reports beneficial ownership of 1,363,346 AdvanSix common shares. These shares are held with sole voting power and sole dispositive power, and no shared voting or dispositive power is reported for this position.

Who are the reporting persons in this AdvanSix (ASIX) Schedule 13G?

The reporting persons are American Century Investment Management, Inc., American Century Companies, Inc., and the Stowers Institute for Medical Research. American Century Investment Management serves as investment adviser to various accounts holding the AdvanSix shares.

What type of control do the filers have over the AdvanSix (ASIX) shares?

The filers report 1,363,346 shares with sole voting power and sole dispositive power. They report zero shared voting power and zero shared dispositive power over the AdvanSix common stock covered by this filing.

Do any individual clients of American Century hold over 5% of AdvanSix (ASIX)?

No individual client does. The filing states that, for accounts advised by American Century Investment Management, Inc., not more than 5% of the AdvanSix common stock class is owned by any single client account.

What is the role of Stowers Institute in this AdvanSix (ASIX) ownership filing?

The Stowers Institute for Medical Research appears as a reporting person as the control entity of American Century Companies, Inc. It is identified in connection with subsidiaries that beneficially own the AdvanSix securities reported.

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

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Available on EDGAR 08/14/2026 - 02:30 PM Accepted by SEC EDGAR 08/14/2026 - 02:29 PM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

AdvanSix Inc.

(Name of Issuer)

Common Stock

(Title of Class of Securities)

(CUSIP Number)

06/30/2026

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

schemaVersion:

SCHEDULE 13G

CUSIP No.

1

Names of Reporting Persons

American Century Investment Management, Inc.

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 1,363,346.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 1,363,346.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,363,346.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

5.1 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

CUSIP No.

1

Names of Reporting Persons

American Century Companies, Inc.

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 1,363,346.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 1,363,346.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,363,346.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

5.1 %

12

Type of Reporting Person (See Instructions)

HC

SCHEDULE 13G

CUSIP No.

1

Names of Reporting Persons

Stowers Institute for Medical Research

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 1,363,346.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 1,363,346.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,363,346.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

5.1 %

12

Type of Reporting Person (See Instructions)

HC

SCHEDULE 13G

Item 1.
(a)	Name of issuer: AdvanSix Inc.
(b)	Address of issuer's principal executive offices: 300 Kimball Drive, Suite 101, Parsippany, New Jersey, 07054
Item 2.
(a)	Name of person filing: American Century Investment Management, Inc. American Century Companies, Inc. Stowers Institute for Medical Research
(b)	Address or principal business office or, if none, residence: 4500 Main Street 9th Floor Kansas City, Missouri 64111
(c)	Citizenship: Delaware
(d)	Title of class of securities: Common Stock
(e)	CUSIP No.:
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: See the response(s) to Item 9 on the attached cover page(s).
(b)	Percent of class: See the response(s) to Item 11 on the attached cover page(s).
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: See the response(s) to Item 5 on the attached cover page(s).
	(ii) Shared power to vote or to direct the vote: See the response(s) to Item 6 on the attached cover page(s).
	(iii) Sole power to dispose or to direct the disposition of: See the response(s) to Item 7 on the attached cover page(s).
	(iv) Shared power to dispose or to direct the disposition of: See the response(s) to Item 8 on the attached cover page(s).
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. Various persons, including the investment companies and separate institutional investor accounts that American Century Investment Management, Inc. ("ACIM") serves as investment adviser, have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the securities that are the subject of this schedule. Except as may be otherwise indicated if this is a joint filing, not more than 5% of the class of securities that is the subject of this schedule is owned by any one client advised by ACIM.
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	If a parent holding company has filed this schedule, pursuant to Rule 13d-1(b)(ii)(G), so indicate under Item 3(g) and attach an exhibit stating the identity and the Item 3 classification of the relevant subsidiary. If a parent holding company has filed this schedule pursuant to Rule 13d-1(c) or Rule 13d-1(d), attach an exhibit stating the identification of the relevant subsidiary. This Item identifies each subsidiary of American Century Companies, Inc. ("ACC"), which is controlled by the Stowers Institute for Medical Research, that is a beneficial owner of securities that are subject of this schedule (the "Subject Securities"). American Century Investment Management, Inc. ("ACIM") is a wholly-owned subsidiary of ACC and an investment adviser registered under Section 203 of the Investment Advisers Act of 1940.
Item 8.	Identification and Classification of Members of the Group.
	If a group has filed this schedule pursuant to §240.13d-1(b)(1)(ii)(K), so indicate under Item 3(k) and attach an exhibit stating the identity and Item 3 classification of each member of the group. If a group has filed this schedule pursuant to §240.13d-1(c) or §240.13d-1(d), attach an exhibit stating the identity of each member of the group. Not applicable
Item 9.	Notice of Dissolution of Group.
	Notice of dissolution of a group may be furnished as an exhibit stating the date of the dissolution and that all further filings with respect to transactions in the security reported on will be filed, if required, by members of the group, in their individual capacity. See Item 5. Not applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

American Century Investment Management, Inc.

Signature:	American Century Investment Management, Inc.
Name/Title:	/s/ John Pak / Senior Vice President
Date:	08/14/2026

American Century Companies, Inc.

Signature:	American Century Companies, Inc.
Name/Title:	/s/ John Pak / Senior Vice President
Date:	08/14/2026

Stowers Institute for Medical Research

Signature:	Stowers Institute for Medical Research
Name/Title:	/s/ Joselyn Verschelden / Authorized Signer
Date:	08/14/2026

Exhibit Information

EXHIBIT Each of the undersigned hereby agrees and consents to the execution and joint filing on its behalf by American Century Investment Management, Inc. of this Schedule 13G respecting the beneficial ownership of the securities which are the subject of this schedule. Dated this 14th day of August, 2026. AMERICAN CENTURY INVESTMENT MANAGEMENT, INC. ("ACIM") AMERICAN CENTURY COMPANIES, INC. ("ACC") By: __/s/ John Pak___________________ John Pak Senior Vice President, ACIM and ACC STOWERS INSTITUTE FOR MEDICAL RESEARCH, solely in its capacity as control entity of ACC By: __/s/ Joselyn Verschelden_________ Joselyn Verschelden Authorized Signer