SEI Investments: Loomis Sayles reports 6.5% stake

Available on EDGAR 11/12/2026 - 09:35 AM EST Accepted by SEC EDGAR 11/12/2026 - 09:34 AM EST Learn about SEC filing dates

Rhea-AI Filing Summary

SEI Investments Co. (SEIC) shares are the subject of an amended ownership report: investment manager Loomis, Sayles & Co., L.P. reported beneficial ownership of 7,803,457.35 shares, or 6.5% of the class, as of September 30, 2026. The manager reported sole voting power over 6,477,211 shares and zero shared voting power; it reported zero sole and shared dispositive power.

Key Figures

Beneficially owned shares: 7,803,457.35 shares Percent of class: 6.5% Sole voting power: 6,477,211 shares +3 more

6 metrics

Beneficially owned shares 7,803,457.35 shares Reported as of September 30, 2026

Percent of class 6.5% Loomis, Sayles & Co., L.P.'s reported beneficial ownership as of September 30, 2026

Sole voting power 6,477,211 shares Reported as of September 30, 2026

Shared voting power 0 shares Reported as of September 30, 2026

Sole dispositive power 0 shares Reported as of September 30, 2026

Shared dispositive power 0 shares Reported as of September 30, 2026

Key Terms

beneficially owned, sole voting power, shared voting power, sole dispositive power

4 terms

beneficially owned technical

"Aggregate amount beneficially owned by each reporting person"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

sole voting power technical

"Sole power to vote or to direct the vote"

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.

shared voting power technical

"Shared power to vote or to direct the vote"

Shared voting power occurs when two or more parties jointly have the right to vote or decide how a block of company shares is cast, like co-owners who must agree before moving a piece of furniture. Investors care because who controls voting rights affects board elections, major corporate decisions and takeover outcomes, and shared control can alter regulatory disclosures and the practical influence any holder has over a company’s direction and value.

sole dispositive power technical

"Sole power to dispose or to direct the disposition"

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.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How many SEIC shares did Loomis, Sayles & Co. report owning?

Loomis, Sayles & Co., L.P. reported beneficial ownership of 7,803,457.35 SEI Investments Co. common shares, equal to 6.5% of the class, as of September 30, 2026. It listed sole voting power over 6,477,211 shares.

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

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SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 20)

SEI Investments Co

(Name of Issuer)

Common Stock

(Title of Class of Securities)

784117103

(CUSIP Number)

09/30/2026

(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 Number(s): 784117103

1

Names of Reporting Persons

Loomis, Sayles & Co., L.P.

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 6,477,211.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

7,803,457.35

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)

6.5 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

Item 1.
(a)	Name of issuer: SEI Investments Co
(b)	Address of issuer's principal executive offices: 1 FREEDOM VALLEY DRIVE, OAKS, PA, 19456-1100
Item 2.
(a)	Name of person filing: Loomis, Sayles & Co., L.P.
(b)	Address or principal business office or, if none, residence: One Financial Center Boston, MA 02111
(c)	Citizenship: United States
(d)	Title of class of securities: Common Stock
(e)	CUSIP No.: 784117103
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: 7803457.35
(b)	Percent of class: 6.5 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 6477211.0
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 0
	(iv) Shared power to dispose or to direct the disposition of: 0
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. Clients of Reporting Person have such a right, none of whom has such interest relating to more than 5% of any class.
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	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 andare held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect ofchanging or influencing the control of the issuer of the securities and were not acquired and are not held in connection withor as a participant in any transaction having that purpose or effect, other than activities solely in connection with anomination 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.

Loomis, Sayles & Co., L.P.

Signature:	Mari Shimokawa
Name/Title:	Deputy Chief Compliance Officer
Date:	11/12/2026