Loomis, Sayles reports 7.1% stake in SEI Investments Co (NASDAQ: SEIC)

Rhea-AI Filing Summary

SEI Investments Co: Loomis, Sayles & Co., L.P. files an amended Schedule 13G reporting beneficial ownership of 8,683,519.78 shares of SEI Investments Co common stock, representing 7.1% of the class. The filing shows sole voting power over 7,130,873 shares and states these holdings are held on behalf of clients. The amendment was signed on 05/14/2026.

Insights

Institutional Ownership Analyst

Loomis, Sayles reports a substantial passive stake (7.1%) held for clients.

The amendment lists 8,683,519.78 shares beneficially owned with 7,130,873 shares subject to sole voting power as of the filing signature on 05/14/2026. The schedule indicates holdings are held for multiple clients, none exceeding 5% individually.

Cash‑flow treatment and any planned dispositions are not disclosed in the excerpt; subsequent filings would show changes in position or voting intentions if made.

Compliance & Proxy Specialist

Amendment clarifies beneficial ownership and voting authority under Schedule 13G/A.

The filing follows the Schedule 13G/A format: it lists issuer CUSIP 784117103, reporting person address, and a declaration that clients hold the economic interest. Item 6 notes clients have dividend/proceeds rights but no single client holds >5%.

Ownership percentages and voting counts are explicit; the filing does not state any activist intent or plans to change holdings.

Key Figures

CUSIP: 784117103 Beneficially owned: 8,683,519.78 shares Percent of class: 7.1% +3 more

6 metrics

CUSIP 784117103 SEI Investments Co common stock

Beneficially owned 8,683,519.78 shares Amount reported in Item 4 of the Schedule 13G/A

Percent of class 7.1% Percent of SEI Investments Co common stock

Sole voting power 7,130,873 shares Number of shares with sole power to vote reported in Item 4

Amendment signature date 05/14/2026 Signature date on the amended Schedule 13G/A

Reporting person citizenship United States Loomis, Sayles & Co., L.P. citizenship listed in Item 2

Key Terms

Beneficially owned, Sole voting power, Schedule 13G/A

3 terms

Beneficially owned regulatory

"Item 4 lists "Amount beneficially owned: 8683519.78""

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 regulatory

"Item 4 shows "Sole power to vote or to direct the vote: 7130873.0""

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.

Schedule 13G/A regulatory

"Header shows "(Amendment No. 18 )" and form type Schedule 13G/A"

A Schedule 13G/A is an amended public filing with the U.S. securities regulator that updates a previous Schedule 13G, disclosing when an individual or group holds a substantial (typically over 5%) stake in a company and is claiming a passive, non‑controlling intent. Investors monitor these updates because rising or falling holdings can signal changing confidence, potential future moves, or shifts in voting power — like watching a public ledger where large shareholders quietly adjust their positions.

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

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Accepted by SEC EDGAR 05/14/2026 - 02:48 PM Learn about SEC filing dates

FAQ

What stake does Loomis, Sayles report in SEIC?

Loomis, Sayles reports beneficial ownership of 8,683,519.78 shares, equal to 7.1% of SEI Investments Co common stock, as stated in Item 4 of the amendment.

How many shares does Loomis, Sayles have voting power over in SEIC?

The filing reports sole voting power over 7,130,873 shares and 0 shared voting power, per the Item 4 voting-power breakdown in the amendment.

Are the reported SEIC shares held for Loomis, Sayles itself or for clients?

The amendment states the shares are held on behalf of clients of the reporting person; Item 6 clarifies clients have dividend/proceeds rights and no single client exceeds 5% of the class.

What is the CUSIP and filing date on the Schedule 13G/A for SEIC?

The CUSIP reported is 784117103. The amendment is signed on 05/14/2026; the cover also references 03/31/2026 in the header of the excerpt.

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)

03/31/2026

(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 7,130,873.00
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

8,683,519.78

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)

7.1 %

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: 8683519.78
(b)	Percent of class: 7.1 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 7130873.0
	(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:	05/14/2026