As filed with the Securities and Exchange Commission on June 13, 2023

Securities Act File No. 333-269553

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

FORM N-14

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933
Pre-Effective Amendment No.	☐
Post-Effective Amendment No. 1	☒

COLUMBIA ACORN TRUST

(Exact Name of Registrant as Specified in Charter)

71 S. Wacker, Suite 2500

Chicago, Illinois 60606

Telephone number: 312.634.9200

Ryan C. Larrenaga, Esq. c/o Columbia Management Investment Advisers, LLC 290 Congress Street Boston, MA 02210 Stephen Kusmierczak Daniel J. Beckman Columbia Acorn Trust 71 S. Wacker, Suite 2500 Chicago, Illinois 60606 Mary C. Moynihan Perkins Coie LLP 700 13th Street, N.W., Suite 800 Washington, D.C. 20005

(Name and Address of Agents for Service)

TITLE OF SECURITIES BEING REGISTERED:

The Information Statement/Prospectus as filed by the Registrant pursuant to Rule 497(b) under the Securities Act of 1933 with the Commission on February 13, 2023 (File No.: 333-269553) (0001193125-23-035190) constitutes Part A of this Post-Effective Amendment No. 1 and is incorporated herein by reference.

The Statement of Additional Information dated February 10, 2023, as filed by the Registrant on Form N-14 (File No.: 333-269553) (0001193125-23-023863) (the “Registration Statement”) constitutes Part B of this Post-Effective Amendment No. 1 and is incorporated herein by reference.

This Post-Effective Amendment No.1 relates solely to Class A, Class Adv, Class C, Class Inst, Class Inst2 and Class Inst3 shares of Columbia Acorn Fund, a series of the Registrant. This Post-Effective Amendment No. 1 is being filed for the sole purpose of adding to Part C of the Registration Statement (i) the executed tax opinion of Perkins Coie LLP supporting the tax matters discussed in the Information Statement/Prospectus and (ii) a Fee Waiver/Expense Reimbursement Agreement between the Registrant and Columbia Wanger Asset Management, LLC relating to Columbia Acorn Fund.

COLUMBIA ACORN TRUST

PART C

OTHER INFORMATION

PART C. OTHER INFORMATION

Item 15. Indemnification

Article VIII of the Agreement and Declaration of Trust of the Registrant (listed as Exhibit 1(a) and incorporated in this filing by reference) provides in effect that Registrant shall provide certain indemnification of its trustees and officers. In accordance with Section 17(h) of the Investment Company Act of 1940, as amended, that provision shall not protect any trustee or officer against any liability to the Registrant or its shareholders to which he would otherwise be subject by reason of willful misfeasance, bad faith, gross negligence or reckless disregard of the duties involved in the conduct of his office.

Insofar as indemnification for liabilities arising under the Securities Act of 1933, as amended (the “Securities Act”) may be permitted to trustees, officers and controlling persons of the Registrant pursuant to the foregoing provisions, or otherwise, the Registrant has been advised that in the opinion of the Securities and Exchange Commission such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the Registrant of expenses incurred or paid by a trustee, officer or controlling person of the Registrant in the successful defense of any action, suit or proceeding) is asserted by such trustee, officer or controlling person in connection with the securities being registered, the Registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act and will be governed by the final adjudication of such issue.

The Registrant has entered into Indemnification Agreements with each of the independent trustees which provide that the Registrant shall indemnify and advance expenses to the independent trustees as provided in the Indemnification Agreements and otherwise to the fullest extent permitted by applicable law. The Registrant will indemnify the independent trustees from and against any and all judgments, penalties, fines and amounts paid in settlement, and all expenses actually and reasonably incurred by the independent trustees in connection with a proceeding to which he or she is a party to by reason of his or her position as an independent trustee. The Registrant will not indemnify the independent trustees for monetary settlements or judgments relating to insider trading, disgorgements of profits pursuant to Section 16(b) of the Securities Exchange Act of 1934, as amended, or any liability to the Registrant or its shareholders with respect to a final adjudication that an action or omission by an independent trustee was committed in bad faith, involved active or deliberate dishonesty, or that the trustee engaged in willful misfeasance, bad faith, gross negligence or reckless disregard of his or her duties.

The Registrant, its trustees and officers, its investment adviser and persons affiliated with them are insured under policies of insurance maintained by Registrant and its investment adviser, respectively, within the limits and subject to the limitations of the policies, against certain expenses in connection with the defense of actions, suits or proceedings, and certain liabilities that might be imposed as a result of such actions, suits or proceedings, to which they are parties by reason of being or having been such trustees or officers. The policies expressly excludes coverage for any trustee or officer whose personal dishonesty, fraudulent breach of trust, lack of good faith, or intention to deceive or defraud has been finally adjudicated or may be established or who willfully fails to act prudently.

Item 16. Exhibits

Note: As used herein, the term “Post-effective Amendment” refers to a post-effective amendment to the registration statement of Registrant or its predecessor, The Acorn Fund, Inc., under the Securities Act of 1933 on form S-5, N-1 or N-1A, no. 2-34223.

Certain exhibits included at this Item 16 are no longer current as of the date of this Post-Effective Amendment No. 1 to the Registrant’s registration statement on Form N-14. The Registrant’s current exhibits are included at Item 28 of post-effective amendment No. 116 to the Registrant’s registration statement on Form N-1A filed on April 27, 2023.

(1)	(a) Agreement and Declaration of Trust. (1)
(1)	(b) Amendment No. 1 to Agreement and Declaration of Trust. (3)
(1)	(c) Amendment No. 2 to Agreement and Declaration of Trust. (4)
(2)	Bylaws dated September 28, 2004, as amended through June 10, 2020. (18)
(3)	Not applicable.
(4)	Agreement and Plan of Reorganization, dated December 22, 2022. (18)
(5)	Not applicable.
(6)	(a)  Organizational Expenses Agreement between Acorn Investment Trust (now known as Columbia Acorn Trust) and Wanger Asset Management, L.P. (now known as Columbia Wanger Asset Management, LLC), dated September 3, 1996. (2)
(6)	(b)  Organizational and Offering Costs Agreement between Columbia Acorn Trust and Columbia Wanger Asset Management, LLC (relating to Columbia Acorn European Fund and Columbia Acorn Emerging Markets Fund) dated August 17, 2011. (9)
(6)	(c) Investment Advisory Agreement between Columbia Acorn Trust and Columbia Wanger Asset Management, LLC dated May  27, 2010, Schedules A and B last amended June 8, 2011. (9)
(6)	(d)  Investment Advisory Fee Reduction Agreement between Columbia Acorn Trust, on behalf of Columbia Acorn International Select, and Columbia Wanger Asset Management, LLC dated July 1, 2016. (14)
(6)	(e)  Investment Advisory Fee Reduction Agreement between Columbia Acorn Trust, on behalf of Columbia Acorn USA, and Columbia Wanger Asset Management, LLC dated May 1, 2022. (17)
(6)	(f) Administrative Services Agreement between Columbia Acorn Trust and Columbia Wanger Asset Management, LLC dated May  1, 2010, (the “Administrative Services Agreement”), Schedule A last amended June 8, 2011. (9)
(6)	(g) Amendment No. 1 dated September 21, 2016 to the Administrative Services Agreement. (14)
(6)	(h) Schedule B to the Administrative Services Agreement, amended September 19, 2019. (15)
(7)	(a) Distribution Agreement between Columbia Acorn Trust and Columbia Management Investment Distributors, Inc. dated May  1, 2010, (the “Distribution Agreement”), Schedules I and II last amended June 8, 2011. (9)
(7)	(b) Amendment dated April 12, 2011 to the Distribution Agreement. (9)
(7)	(c) Amendment No. 2 dated September 21, 2016 to the Distribution Agreement. (14)
(8)	Not applicable.
(9)	Custody Agreement among JPMorgan Chase Bank, N.A., Columbia Acorn Trust and Wanger Advisors Trust dated December  15, 2010, effective July 22, 2011, with Addendums dated July 14, 2011. (9)
(10)	(a) Plan of Distribution Pursuant to Rule 12b-1. (9)
(10)	(b) Rule 12b-1 Plan Implementing Agreement. (9)
(10)	(c) Amended and Restated Plan Pursuant to Rule 18f-3(d), effective February 1, 2021. (16)
(11)	Opinion and consent of Perkins Coie LLP as to the legality of the securities being registered. (18)
(12)	Opinion and consent of Perkins Coie LLP supporting the tax matters discussed in the Information Statement/Prospectus.

(13)	(a)  Amended and Restated Transfer, Dividend Disbursing and Shareholders’ Servicing Agent Agreement between Columbia Acorn Trust and Columbia Management Investment Services Corp. dated May  1, 2012 (the “Transfer Agent Agreement”). (10)
(13)	(b) Amendment No. 1 dated September 21, 2016 to the Transfer Agent Agreement. (13)
(13)	(c) Compliance Agreement between Columbia Acorn Trust and Ameriprise Financial, Inc. dated May 1, 2010. (7)
(13)	(d) Fee Waiver/Expense Reimbursement Agreement between Columbia Acorn Trust and Columbia Wanger Asset Management, LLC, relating to Columbia Acorn International, dated May 1, 2022 (17).
(13)	(e) Fee Waiver/Expense Reimbursement Agreement between Columbia Acorn Trust and Columbia Wanger Asset Management, LLC, relating to Columbia Acorn USA, dated May 1, 2022. (17)
(13)	(f) Fee Waiver/Expense Reimbursement Agreement between Columbia Acorn Trust and Columbia Wanger Asset Management, LLC, relating to Columbia Thermostat Fund, dated May 1, 2022. (17)
(13)	(g) Fee Waiver/Expense Reimbursement Agreement between Columbia Acorn Trust and Columbia Wanger Asset Management, LLC, relating to Columbia Acorn Fund, dated May 1, 2022. (17)
(13)	(h) Fee Waiver/Expense Reimbursement Agreement between Columbia Acorn Trust and Columbia Wanger Asset Management, LLC, relating to Columbia Acorn Fund, dated April 22, 2023.
(13)	(i)  Fee Waiver/Expense Reimbursement Agreement between Columbia Acorn Trust and Columbia Wanger Asset Management, LLC, relating to Columbia Acorn European Fund, dated May 1, 2022. (17)
(13)	(j)  Fee Waiver Agreement, relating to Columbia Acorn International Select, between Columbia Acorn Trust and Columbia Wanger Asset Management, LLC, dated July 1, 2016. (14)
(13)	(k) Fee Waiver Agreement, relating to Columbia Acorn International Select, between Columbia Acorn Trust and Columbia Wanger Asset Management, LLC dated May 1, 2022. (17)
(13)	(l) Transfer Agent Fee Waiver Agreement between Columbia Acorn Trust and Columbia Management Investment Services Corp., dated May 1, 2022. (17)
(13)	(m)  Participation Agreement among Merrill Lynch Life Insurance Company, Columbia Acorn Trust and Columbia Funds Distributor, Inc. (now named Columbia Management Distributors, Inc.) dated March 4, 2005. (5)
(13)	(n) Amendment No.  1 to Participation Agreement among Merrill Lynch Life Insurance Company, Columbia Acorn Trust and Columbia Management Distributors, Inc. (formerly Columbia Funds Distributor, Inc.) dated March 30, 2007. (6)
(13)	(o)  Participation Agreement among ML Life Insurance Company of New York, Columbia Acorn Trust and Columbia Funds Distributor, Inc. (now named Columbia Management Distributors, Inc.) dated March 4, 2005. (5)
(13)	(p) Amendment No.  1 to Participation Agreement among ML Life Insurance Company of New York, Columbia Acorn Trust and Columbia Management Distributors, Inc. (formerly Columbia Funds Distributor, Inc.) dated March 30, 2007. (6)
(14)	Consent of Independent Registered Public Accounting Firm (PricewaterhouseCoopers LLP). (18)
(15)	Not applicable.

(16)	Not applicable.
(17)	(a) Columbia Threadneedle Investments Global Personal Account Dealing and Code of Ethics, effective December 2021. (17)
(17)	(b)  Code of Ethics for Non-Management Trustees, as amended, effective as of September 19, 2012. (11)
1.	Incorporated by reference to post-effective amendment No. 53 to the Registrant’s registration statement on form N-1A, Securities Act registration number 2-34223 (the “Registration Statement”), filed on April 30, 1996.
2.	Incorporated by reference to Registrant’s post-effective amendment No. 61 to the Registration Statement filed on April 30, 1998.
3.	Incorporated by reference to Registrant’s post-effective amendment No. 70 to the Registration Statement filed on May 1, 2001.
4.	Incorporated by reference to Registrant’s post-effective amendment No. 77 to the Registration Statement filed on March 1, 2005.
5.	Incorporated by reference to Registrant’s post-effective amendment No. 79 to the Registration Statement filed on May 1, 2006.
6.	Incorporated by reference to Registrant’s post-effective amendment No. 80 to the Registration Statement filed on April 30, 2007.
7.	Incorporated by reference to Registrant’s post-effective amendment No. 87 to the Registration Statement filed on September 27, 2010.
8.	Incorporated by reference to Registrant’s post-effective amendment No. 88 to the Registration Statement filed April 29, 2009.
9.	Incorporated by reference to Registrant’s post-effective amendment No. 91 to the Registration Statement filed on August 17, 2011.
10.	Incorporated by reference to Registrant’s post-effective amendment No. 93 to the Registration Statement filed on April 27, 2012.
11.	Incorporated by reference to Registrant’s post-effective amendment No. 95 to the Registration Statement filed on November 7, 2012.
12.	Incorporated by reference to Registrant’s post-effective amendment No. 99 to the Registration Statement filed on April 30, 2014.
13.	Incorporated by reference to Registrant’s post-effective amendment No. 103 to the Registration Statement filed on April 29, 2016.
14.	Incorporated by reference to Registrant’s post-effective amendment No. 105 to the Registration Statement filed on April 28, 2017.
15.	Incorporated by reference to Registrant’s post-effective amendment No. 112 to the Registration Statement filed on April 29, 2020.
16.	Incorporated by reference to Registrant’s post-effective amendment No. 114 to the Registration Statement filed on April 28, 2021.
17.	Incorporated by reference to Registrant’s post-effective amendment No. 115 to the Registration Statement filed on April 28, 2022.
18.	Incorporated by reference to Registrant’s registration statement on Form N-14 (File No. 333-269553) filed on February 3, 2023.

Item 17. Undertakings

(1) The undersigned registrant agrees that prior to any public reoffering of the securities registered through the use of a prospectus which is a part of this registration statement by any person or party who is deemed to be an underwriter within the meaning of Rule 145(c) of the Securities Act, the reoffering prospectus will contain the information called for by the applicable registration form for reofferings by persons who may be deemed underwriters, in addition to the information called for by the other items of the applicable form.

(2) The undersigned registrant agrees that every prospectus that is filed under paragraph (1) above will be filed as a part of an amendment to the registration statement and will not be used until the amendment is effective, and that, in determining any liability under the 1933 Act, each post-effective amendment shall be deemed to be a new registration statement for the securities offered therein, and the offering of the securities at that time shall be deemed to be the initial bona fide offering of them.

SIGNATURES

As required by the Securities Act of 1933, this Post-Effective Amendment No. 1 to the Registration Statement on Form N-14 has been signed on behalf of the Registrant, Columbia Acorn Trust, by the undersigned, duly authorized, in the City of Chicago, and State of Illinois on the 13th day of June, 2023.

COLUMBIA ACORN TRUST
By:	/s/ Stephen Kusmierczak
	Stephen Kusmierczak, Co-President
By:	/s/ Daniel J. Beckman
	Daniel J. Beckman, Co-President

Pursuant to the requirements of the Securities Act of 1933, this Registration Statement has been signed below by the following persons in the capacities indicated on dates indicated.

Name	Title	Date
/S/ DAVID J. RUDIS David J. Rudis	Trustee	June 13, 2023
/S/ MAUREEN M. CULHANE Maureen M. Culhane	Trustee	June 13, 2023
/S/ MARGARET M. EISEN Margaret M. Eisen	Trustee	June 13, 2023
/S/ JOHN C. HEATON John C. Heaton	Trustee	June 13, 2023
/S/ DIANNE F. LOB Dianne F. Lob	Trustee	June 13, 2023
/S/ CHARLES R. PHILLIPS Charles R. Phillips	Trustee	June 13, 2023
/S/ DANIEL J. BECKMAN Daniel J. Beckman	Co-President and Principal Executive Officer	June 13, 2023
/S/ MICHAEL G. CLARKE Michael G. Clarke	Treasurer and Principal Accounting and Financial Officer	June 13, 2023

S-1

Exhibit Index

Exhibit No.	Description
(12)	Opinion and consent of Perkins Coie LLP supporting the tax matters discussed in the Information Statement/Prospectus.
(13)(h)	Fee Waiver/Expense Reimbursement Agreement between Columbia Acorn Trust and Columbia Wanger Asset Management, LLC, relating to Columbia Acorn Fund, dated April 22, 2023.