William Blair (NASDAQ: ACVA) reports 7.21M shares, 4.1% stake

Rhea-AI Filing Summary

William Blair Investment Management, LLC filed Amendment No. 3 to a Schedule 13G/A reporting beneficial ownership of 7,212,623 shares of ACV Auctions Inc. common stock, equal to 4.1% of the class. The filing lists sole voting power for 6,450,024 shares and sole dispositive power for 7,212,623 shares. The form is signed by the firm's Chief Compliance Officer on 05/07/2026.

Key Figures

Beneficially owned: 7,212,623 shares Percent of class: 4.1% Sole voting power: 6,450,024 shares +2 more

5 metrics

Beneficially owned 7,212,623 shares Amount beneficially owned reported on the Schedule 13G/A

Percent of class 4.1% Percent of the common stock class reported in Item 4

Sole voting power 6,450,024 shares Number of shares William Blair has sole power to vote

Sole dispositive power 7,212,623 shares Number of shares William Blair has sole power to dispose

Shared voting/dispositive power 0 shares No shared voting or shared dispositive power reported

Key Terms

Schedule 13G/A, Beneficial ownership, Sole dispositive power

3 terms

Schedule 13G/A regulatory

"Amendment No. 3 to a Schedule 13G/A reporting beneficial ownership"

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.

Beneficial ownership regulatory

"Amount beneficially owned: 7,212,623 (b) Percent of class: 4.1%"

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 dispositive power regulatory

"Sole power to dispose or to direct the disposition of: 7,212,623"

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.

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SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 3)

ACV Auctions Inc.

(Name of Issuer)

Common Stock

(Title of Class of Securities)

00091G104

(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): 00091G104

1

Names of Reporting Persons

WILLIAM BLAIR INVESTMENT MANAGEMENT, LLC

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 6,450,024.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 7,212,623.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

7,212,623.00

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)

4.1 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

Item 1.
(a)	Name of issuer: ACV Auctions Inc.
(b)	Address of issuer's principal executive offices: 640 ELLICOTT STREET, 640 ELLICOTT STREET, BUFFALO, NEW YORK, 14203.
Item 2.
(a)	Name of person filing: William Blair Investment Management, LLC
(b)	Address or principal business office or, if none, residence: 150 North Riverside Plaza, Chicago, IL 60606
(c)	Citizenship: Delaware
(d)	Title of class of securities: Common Stock
(e)	CUSIP No.: 00091G104
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: 7,212,623
(b)	Percent of class: 4.1%
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 6,450,024
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 7,212,623
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
	Ownership of 5 percent or less of a class
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	Not Applicable
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 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.

WILLIAM BLAIR INVESTMENT MANAGEMENT, LLC

Signature:	Telmo Martins
Name/Title:	Chief Compliance Officer
Date:	05/07/2026

FAQ

How many ACV Auctions (ACVA) shares does William Blair report owning?

William Blair reports beneficial ownership of 7,212,623 shares. The filing states this equals 4.1% of the outstanding common stock and shows sole dispositive power over those shares.

What voting power does William Blair hold in ACV Auctions (ACVA)?

The firm reports sole voting power for 6,450,024 shares. The filing lists no shared voting power and indicates the firm can direct the vote for that number of shares.

When was the Schedule 13G/A amendment signed for ACV Auctions (ACVA)?

The amendment is signed by the Chief Compliance Officer on 05/07/2026. The cover references 03/31/2026 in connection with the common stock CUSIP on the form.

Does William Blair share dispositive or voting power over ACV Auctions shares?

No shared powers are reported. The filing shows 0 shared voting power and 0 shared dispositive power, indicating sole control as listed.

What type of filing is this for ACV Auctions (ACVA)?

This document is an Amendment No. 3 to a Schedule 13G/A, used to report passive or qualifying beneficial ownership changes in common stock under applicable SEC rules.