Loomis Sayles holds 7.04% of SEI Investments

Loomis, Sayles & Co., L.P. reports beneficial ownership of SEI Investments Co common stock on a Schedule 13G/A. It reports 8,462,120.64 shares beneficially owned, representing 7.04% of the common stock.

Rhea-AI Filing Summary

Loomis, Sayles & Co., L.P. reports beneficial ownership of SEI Investments Co common stock on a Schedule 13G/A. It reports 8,462,120.64 shares beneficially owned, representing 7.04% of the common stock. Loomis Sayles has sole voting power over 6,989,367 shares, with no shared voting power and no sole or shared dispositive power. Economic rights to dividends and sale proceeds belong to its clients, and no individual client has an interest exceeding 5% of the class.

Key Figures

Beneficial ownership: 8,462,120.64 shares Percent of class: 7.04% Sole voting power: 6,989,367 shares +5 more

8 metrics

Beneficial ownership 8,462,120.64 shares Common stock of SEI Investments Co reported by Loomis, Sayles & Co., L.P.

Percent of class 7.04% Portion of SEI Investments Co common stock beneficially owned

Sole voting power 6,989,367 shares Shares over which Loomis, Sayles & Co., L.P. has sole power to vote

Shared voting power 0 Shares over which voting power is shared

Sole dispositive power 0 Shares over which Loomis, Sayles & Co., L.P. can solely direct disposition

Shared dispositive power 0 Shares over which disposition power is shared

Amendment number 18 Amendment No. 18 to Schedule 13G for SEI Investments Co

Signature date 08/14/2026 Date signed by Deputy Chief Compliance Officer Mari Shimokawa

Key Terms

beneficially owned, Sole Voting Power, dispositive power, Schedule 13G, +1 more

5 terms

beneficially owned financial

"Item 4. | Ownership (a) | Amount beneficially owned: 8462120.64"

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 financial

"5 | Sole Voting Power 6,989,367.00 6 | Shared Voting Power"

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.

dispositive power financial

"(iii) Sole power to dispose or to direct the disposition of: 0"

Dispositive power is the authority to decide the final outcome of an asset, legal claim, contract, or corporate action — in effect the power to dispose of or resolve something. For investors it matters because whoever holds that authority can determine who gets paid, who controls an asset or vote, and how risks and returns are allocated; think of it like holding the key that lets you lock in the winner or loser in a deal.

Schedule 13G regulatory

"Ownership of more than 5 Percent on Behalf of Another Person."

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.

percent of class financial

"(b) | Percent of class: 7.04 %"

Percent of class is the portion of a specific category of securities—such as a company’s common shares, preferred shares, or a bond series—that takes part in or approves a corporate action (vote, consent, tender, etc.). Investors watch this number because it reveals how much support or opposition exists within that particular shareholder group; like counting how many members of a club back a proposal, it can determine whether a plan passes or how influence is distributed.

FAQ

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

What percentage of SEIC does Loomis, Sayles & Co., L.P. report owning?

Loomis, Sayles & Co., L.P. reports beneficial ownership of 7.04% of SEI Investments Co common stock. This percentage is based on 8,462,120.64 shares attributed to its clients under its management.

How many SEIC shares does Loomis, Sayles & Co., L.P. beneficially own?

Loomis, Sayles & Co., L.P. beneficially owns 8,462,120.64 shares of SEI Investments Co common stock. These shares are held for its clients, who retain the economic rights to dividends and sale proceeds.

What voting power does Loomis, Sayles & Co., L.P. have over SEIC shares?

Loomis, Sayles & Co., L.P. has sole voting power over 6,989,367 shares of SEI Investments Co common stock and no shared voting power. It also reports no sole or shared dispositive power over any shares.

Do Loomis, Sayles & Co., L.P. clients hold more than 5% of SEIC individually?

Loomis, Sayles & Co., L.P. states its clients have rights to dividends and sale proceeds for the reported shares, but no individual client has an interest relating to more than 5% of any class of SEI Investments Co securities.

What type of filing did Loomis, Sayles & Co., L.P. submit for SEIC?

Loomis, Sayles & Co., L.P. submitted an Amendment No. 18 to Schedule 13G regarding SEI Investments Co (SEIC) common stock, updating its reported beneficial ownership and voting power information.

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

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Accepted by SEC EDGAR 08/14/2026 - 10:42 AM EDT Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 18)

SEI Investments Co

(Name of Issuer)

Common Stock

(Title of Class of Securities)

784117103

(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 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 6,989,367.00
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

8,462,120.64

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)

7.04 %

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: 8462120.64
(b)	Percent of class: 7.04 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 6989367.0
	(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:	08/14/2026