NMZ Nuveen Municipal High Income Opportunity Fund

SCHEDULE 13D

CUSIP No. 670682871

SCHEDULE 13D

CUSIP No. 670682871

This Statement on Schedule 13D (the “Statement”) relates to the purchase by Capital Strategies (as defined below) of 1,700 Adjustable Rate MuniFund Term Preferred Shares, Series 2031 (CUSIP No. 670682871) (the “AMTP Shares”) of Nuveen Municipal High Income Opportunity Fund (the “Issuer” or the “Company”). This Statement is being filed by the Reporting Persons (as defined below) as a result of the transition of the AMTP Shares to Capital Strategies (as defined below). The Issuer’s principal executive offices are located at 333 W. Wacker Drive, Chicago, Illinois 60606.

This Statement is being filed on behalf of each of the following persons (collectively, the “Reporting Persons”):

This Statement relates to the AMTP Shares that were purchased for the account of Capital Strategies.

The address of the principal business office of Wells Fargo is:

420 Montgomery Street

San Francisco, CA 94104

The address of the principal business office of Capital Strategies is:

30 Hudson Yards

New York, NY 10001

Wells Fargo provides a diversified set of banking, investment and mortgage products and services, as well as consumer and commercial finance, through its four reportable operating segments: Consumer Banking and Lending, Commercial Banking, Corporate and Investment Banking, and Wealth and Investment Management.

Information concerning each executive officer, director and controlling person (the “Listed Persons”) of the Reporting Persons is listed on Schedule I attached hereto, and is incorporated by reference herein. To the knowledge of the Reporting Persons, all of the Listed Persons are citizens of the United States, other than as otherwise specified on Schedule I hereto.

Other than as set forth on Schedule II, during the last five years, none of the Reporting Persons, and to the best knowledge of the Reporting Persons, none of the Listed Persons, have been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors) or was a party to a civil proceeding of a judicial or administrative body of competent jurisdiction as a result of which such person was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws, or finding any violation with respect to such laws.

The aggregate amount of funds used by the Reporting Persons to purchase the securities reported herein was approximately $170,000,000. The source of funds was the working capital of the Reporting Persons.

The Reporting Persons declare that neither the filing of this Statement nor anything herein shall be construed as an admission that such person is, for the purposes of Section 13(d) of the Exchange Act or any other purpose, (i) acting (or has agreed or is agreeing to act together with any other person) as a partnership, limited partnership, syndicate, or other group for the purpose of acquiring, holding or disposing of securities of the Company or otherwise with respect to the Company or any securities of the Company or (ii) a member of any group with respect to the Company or any securities of the Company.

Capital Strategies purchased the AMTP Shares for investment purposes. Capital Strategies acquired the AMTP Shares in connection with a transition of the shares coordinated by the Issuer and conducted pursuant to the terms of that certain AMTP Transition Agreement, dated April 3, 2023 between the Company and Capital Strategies (the “Transition Agreement”) for an aggregate purchase price of $170,045,830 (which included a liquidation preference of $100,000 per share and accrued dividends of $26.9589 per share).

The Reporting Persons have not acquired the subject securities with any purpose, or with the effect of, changing or influencing control of the issuer, or in connection with or as a participant in any transaction having that purpose or effect.

(a) - (b) The responses of the Reporting Persons to Rows (7) through (11) of the cover pages of this Statement are incorporated herein by reference.

(c) The responses of the Reporting Persons in Item 3 and Item 4 are incorporated herein by reference.

(d) No other person is known by the Reporting Persons to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, AMTP Shares that may be deemed to be beneficially owned by the Reporting Persons.

(e) Not applicable.

The responses of the Reporting Persons to Item 4 are incorporated herein by reference. With respect to the AMTP Shares owned by Capital Strategies, on April 3, 2023, Capital Strategies assigned certain preferred class voting rights on the AMTP Shares to a voting trust (the “Voting Trust”) created pursuant to the Voting Trust Agreement, dated April 3, 2023 among Capital Strategies, Lord Securities Corporation, as voting trustee (the “Voting Trustee”) and Institutional Shareholder Services Inc. (the “Voting Consultant”). Voting and consent rights on the AMTP Shares not assigned to the Voting Trust have been retained by Capital Strategies. The Voting Trust provides that with respect to voting or consent matters relating to the voting rights assigned to the Voting Trust, the Voting Consultant analyzes such voting or consent matters and makes a recommendation to the Voting Trustee on voting or consenting. The Voting Trustee is obligated to follow any such recommendations of the Voting Consultant when providing a vote or consent. Capital Strategies has the right to cause the Company to register the AMTP Shares pursuant to a Registration Rights Agreement, dated April 3, 2023 between the Company and Capital Strategies.

SIGNATURES

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.

Date: April 12, 2023

LIST OF EXHIBITS

SCHEDULE I

EXECUTIVE OFFICERS AND DIRECTORS OF REPORTING PERSONS

The following sets forth the name and present principal occupation of each executive officer and director of Wells Fargo & Company. The business address of each of the executive officers and directors of Wells Fargo & Company is 420 Montgomery Street, San Francisco, CA 94104.

The following sets forth the name and present principal occupation of each executive officer and director of Wells Fargo Municipal Capital Strategies, LLC. The business address of each of the executive officers and directors of Wells Fargo Municipal Capital Strategies, LLC is 30 Hudson Yards, New York, NY 10001.

SCHEDULE II

LITIGATION SCHEDULE

FINRA/EXCHANGE REPORTING SETTLEMENTS From time to time Wells Fargo broker-dealers resolve technical trade reporting issues relating to timing and other data elements with the Financial Industry Regulatory Authority (“FINRA”) and exchanges involving small numbers of trades processed by the firms. Resolutions of this type during the relevant period typically included fines of less than $100,000 each.

STATE OF MISSOURI SETTLEMENT On February 16, 2017, A.G. Edwards (k/n/a Wells Fargo Clearing Services, LLC) entered into a Consent Order with the State of Missouri. The action involved a Missouri Resident’s claim that his ex-wife misappropriated over $300,000 out of his IRA account during the period between August 2001 and July 2007, and the State of Missouri alleged a failure by the firm to supervise the completeness and accuracy of the early IRA distribution forms associated with the withdrawals. Without admitting or denying liability, the firm consented to a censure and agreed to pay $25,672.17 to the Missouri Secretary of State’s Investor Education Fund to fully resolve the matter.

FINRA SETTLEMENT On May 16, 2017, FINRA announced a settlement with Wells Fargo Clearing Services, LLC and Wells Fargo Advisors Financial Network, LLC concerning unsuitable recommendations and supervisory failures in relation to sales of certain non-traditional exchange traded products (“ETPs”) in violation of FINRA and NASD rules for the period July 1, 2010 to May 1, 2012. Without admitting or denying the findings, the firms accepted a censure and agreed to pay restitution to certain clients totaling $3,411,478.78.

FINRA SETTLEMENT On June 21, 2017, Wells Fargo Securities, LLC entered into a settlement agreement with FINRA without admitting or denying the allegations of improper reporting of conventional over-the-counter option positions under FINRA large option position reporting rules. The firm consented to a censure, payment of a $3.25 million fine, and an undertaking to review its supervisory systems related to large options position reporting.

SEC ORDER On November 13, 2017, the SEC announced that Wells Fargo Advisors, LLC agreed to settle charges that it violated Section 17(a) of the Securities Exchange Act of 1934 and Rule 17a-8 by failing to file and timely file Suspicious Activity Reports between approximately March 2012 and June 2013. Without admitting or denying the allegations, the firm agreed to a cease and desist order, a censure, and a civil penalty of $3,500,000. Wells Fargo Advisors also agreed to voluntarily undertake a review and update of its policies and procedures and develop and conduct additional training.

STATE OF ILLINOIS SETTLEMENT On December 21, 2017, Wells Fargo Advisors, LLC (k/n/a Wells Fargo Clearing Services, LLC) entered into a Consent Order with the State of Illinois regarding allegations that it received, reviewed and/or analyzed documents and information provided by a financial advisory firm concerning certain money manager strategies that contained false and misleading information. The findings stated that the firm included the financial advisory firm’s money manager strategies in certain of its separately managed account programs, but that the firm did not utilize inaccurate historical performance data in connection with its decision to onboard the money manager strategies and the firm did not incorporate inaccurate performance data in its advertisements or program marketing materials. Without admitting or denying the findings, the Firm agreed to a total monetary payment of $270,000.

NYSE SETTLEMENT On February 2, 2018, Wells Fargo Prime Services, LLC (“WFPS”) and NYSE Arca, Inc. entered into an Offer of Settlement and Consent without admitting or denying any allegations to settle charges of violations of Securities Exchange Act Rule 15c3-5 and NYSE Arca Rule 11.18. The settlement related to an erroneous trade WFPS entered on July 29, 2016. WFPS consented to a fine of $10,000.

STATE OF NEVADA SECURITIES DIVISION RESIDENTIAL OFFICE INVESTIGATION On April 13, 2018, the Nevada Securities Division and Wells Fargo Clearing Services, LLC (“WFCS”) entered into an Administrative Consent Order wherein WFCS admitted to failing to register the residential offices of three Financial Advisors who were working from home. Nevada’s definition of “branch office” includes a personal residence where securities business is transacted, even if the residence is not held out to the public or used for client meetings. WFCS agreed to pay an $8,000 fine and $1,446.13 for the costs of the examinations conducted by the Nevada Securities Division.

SEC SETTLEMENT On June 25, 2018, Wells Fargo Advisors LLC (“WFA”), entered into a settlement agreement with the SEC wherein, without admitting or denying liability, it settled charges of violations of Sections 17(a)(2) and 17(a)(3) of the Securities Act. The settlement related to certain registered representatives soliciting customers to redeem, and short-term trading of, market-linked investments prematurely without adequate analysis or consideration of the substantial costs associated with the transactions. As part of the settlement, the firm consented to a censure and a payment of $5,108,441.27 representing disgorgement, prejudgment interest, and a civil penalty. WFA also lost its Well Known Seasoned Issuer status as a collateral consequence of the settlement.

COMMONWEALTH OF MASSACHUSETTS SECURITIES DIVISION SETTLEMENT On August 26, 2018, the Massachusetts Securities Division of the Office of the Secretary of the Commonwealth and Wells Fargo Clearing Services, LLC (“WFCS”) entered into a Consent Order regarding allegations that certain WFCS supervisors and agents had a lapse in required Massachusetts registration for some period during the relevant time period of January 1, 2016 to June 28, 2018. Without admitting or denying the facts or conclusions of law, WFCS agreed to certain undertakings including payment of an administrative fine of $450,000.

SEC SETTLEMENT On March 11, 2019, the SEC announced that Wells Fargo Advisors, LLC, and Wells Fargo Advisors Financial Network, LLC (collectively “Wells Fargo”) agreed to settle charges, without admitting or denying liability, that Wells Fargo violated Section 203(e) and 203(k) of the Investment Advisers Act of 1940. The settlement relates to Wells Fargo’s voluntary participation in the SEC’s Share Class Selection Disclosure Initiative wherein investment advisers were encouraged to self-report the failure to adequately disclose conflicts of interest associated with the recommendation or selection of a mutual fund share class that charged distribution fees (“12b-1 Fees”) when a lower-cost share class of the same fund existed. The settlement requires Wells Fargo to adhere to a cease-and-desist order and to disgorge $17,363,847.29 in 12b-1 fees through a restitution program. The settlement did not require Wells Fargo to pay any additional fines or penalties given its voluntary participation in the program.

SEC SETTLEMENT On March 20, 2019, the SEC announced that Wells Fargo Securities, LLC had consented to a judgment entered by the federal district court in Rhode Island resolving a 2016 SEC civil action against multiple parties. The matter had arisen out of the firm’s role as placement agent in a $75 million bond offering by the Rhode Island Economic Development Corporation in November 2010 for the purpose of loaning the proceeds to 38 Studios, LLC, an early-stage, pre-revenue videogame development company that was ultimately unable to meet its obligations under the loan. The SEC had alleged that the firm and other defendants had made two material omissions in the bond placement materials. Without admitting or denying liability, the firm consented to injunctions and a penalty of $812,500.

FINRA SETTLEMENT On January 29, 2020, FINRA announced a settlement with Wells Fargo Clearing Services, LLC (“WFCS”) concerning allegations that WFCS violated NASD Rule 3010(a) (for conduct prior to December 1, 2014) and FINRA Rule 3110(a) (for conduct on or after December 1, 2014) by failing to reasonably supervise a former registered representative who excessively traded equity positions in three accounts belonging to an elderly customer during the period from March 2012 to March 2016. Without admitting or denying the findings, Wells Fargo accepted a censure and agreed to pay a fine of $175,000.

SALES PRACTICES SETTLEMENTS On February 21, 2020, Wells Fargo & Company (“WFC”) entered into settlement agreements with the SEC and the DOJ to resolve those agencies’ investigations into WFC’s historical Community Bank sales practices and related disclosures. With respect to the SEC, WFC consented to the entry into of a cease and desist order, which found that WFC violated Section 10(b) of the Exchange Act and Rule 10b-5 thereunder, and agreed to pay a civil penalty of $500 million. With respect to the DOJ, WFC entered into a deferred prosecution agreement with the United States Attorney’s Offices for the Central District of California and the Western District of North Carolina and a settlement agreement with the Civil Division of the DOJ and the United States Attorney’s Office for the Central District of California related to the sales practices conduct and agreed to pay a monetary penalty of $2.5 billion. WFC accepted and acknowledged responsibility for facts and conduct described in the deferred prosecution agreement, and no charges will be filed against WFC provided that WFC abides by all the terms of the agreement.

SEC SETTLEMENT On February 27, 2020, the SEC announced that Wells Fargo Clearing Services, LLC and Wells Fargo Advisors Financial Network (collectively “Wells Fargo”) agreed to settle allegations that, in connection with Wells Fargo’s recommendation that many retail investment advisory clients and brokerage customers buy and hold single-inverse exchange-traded funds (“ETFs”) without having adequate compliance policies and procedures and without providing financial advisors proper training and supervision of single-inverse ETFs, it willfully violated Section 206(4) of the Investment Advisers Act of 1940 and Rule 206(4)-7 thereunder, failed reasonably to fulfill its supervisory responsibilities within the meaning of Section 203(e)(6) of the Advisers Act and failed reasonably to fulfill its supervisory responsibilities within the meaning of Section 15(b)(4)(E) of the Securities Exchange Act of 1934. Without admitting or denying the SEC’s findings, Wells Fargo agreed to consent to: (a) cease and desist from committing or causing any violations and any future violations of Section 206(4) of the Advisers Act and Rule 206(4)-7 thereunder, (b) be censured, and (c) pay a civil monetary penalty in the amount of $35,000,000. The penalty amount was paid into escrow for disbursement to certain Wells Fargo clients who sustained investment losses in single-inverse ETFs.

STATE OF MARYLAND SETTLEMENT On June 15, 2020, Wells Fargo & Company entered into a Consent Order with the Attorney General of the State of Maryland, pursuant to which it agreed to pay $20 million in remediation to resolve claims relating to certain prior residential mortgage-backed securities activities from 2005 to 2009.

FINRA SETTLEMENT On August 28, 2020, FINRA announced a settlement with Wells Fargo Clearing Services, LLC (“WFCS”) concerning allegations that WFCS failed to reasonably supervise the activities of two former financial advisors in violation of FINRA rules between November 2012 and October 2015. Without admitting or denying the findings, WFCS Fargo accepted a censure and agreed to pay a fine of $350,000 and restitution to three clients totaling $201,498.

FINRA SETTLEMENT On September 1, 2020, FINRA announced a settlement with Wells Fargo Clearing Services, LLC and Wells Fargo Advisors Financial Network, LLC (collectively “Wells Fargo”) concerning allegations that Wells Fargo failed to establish and maintain a supervisory system and failed to enforce written supervisory procedures that were reasonably designed to achieve compliance with FINRA’s suitability rule as it pertained to switches from variable annuities to investment company products during the period January 2011 to August 2016. Without admitting or denying the findings, Wells Fargo accepted a censure and agreed to pay fines totaling $675,000 and restitution to clients totaling $1,445,167.50.

FINRA SETTLEMENT On November 4, 2020, FINRA announced a settlement with First Clearing LLC, n/k/a Wells Fargo Clearing Services, LLC (“Wells Fargo”) concerning allegations that Wells Fargo distributed 6,851 account statements to customers containing valuation information for one or more Direct Participation Programs or Real Estate Investment Trusts that did not comply with NASD Rule 2340(c) during the period April 2016 through October 2016. Without admitting or denying the findings, Wells Fargo accepted a censure and agreed to pay a fine of $300,000.

FINRA SETTLEMENT On November 25, 2020, FINRA announced a settlement with Wells Fargo Clearing Services, LLC (“WFCS”) concerning allegations that WFCS (i) failed to make accurate order memoranda in violation of Rule 17a-3(a)(6) of the Securities Exchange Act of 1934 and FINRA Rules 4511 and 2010, and (ii) transmitted inaccurate reports to the Order Audit Trail System in violation of FINRA Rules 7450 and 2010 during the period October 1, 2016 to June 12, 2018. Without admitting or denying the findings, WFCS accepted a censure and agreed to pay a fine of $75,000.

FINRA SETTLEMENT On December 6, 2021, FINRA announced a settlement with Wells Fargo Clearing Services, LLC and Wells Fargo Advisors Financial Network, LLC (“Wells Fargo”) concerning allegations that Wells Fargo failed to store records related to its Customer Identification Program (“CIP”) in the required Write Once, Read Many (“WORM”) format. The findings also stated that when the issue was initially discovered it was not escalated to the appropriate group to determine if it need to be reported to FINRA nor was it remediated at that time. The issue has since been remediated and CIP records are now being stored on a WORM-compliant platform. Without admitting or denying the findings, Wells Fargo accepted a censure and agreed to pay a fine of $2,250,000.

FINRA SETTLEMENT On December 20, 2021, FINRA announced a settlement with Wells Fargo Clearing Services, LLC and Wells Fargo Advisors Financial Network, LLC (“Wells Fargo”) concerning allegations that Wells Fargo failed to establish and maintain a supervisory system reasonably designed to supervise representatives’ 529 plan share-class recommendations in violation of MSRB Rule G-27 during the period January 1, 2011, and December 4, 2016. Without admitting or denying the findings, Wells Fargo accepted a censure and agreed to pay restitution of $3,367,929 plus interest.

FINRA SETTLEMENT On December 13, 2021, FINRA announced a settlement with Wells Fargo Clearing Services, LLC and Wells Fargo Advisors Financial Network, LLC (“Wells Fargo”) concerning gations of unsuitable recommendations and supervisory failures in relation to unit investment trusts in violation of FINRA and NASD rules for the period July 2013 to June 2018. Without admitting or denying the findings, Wells Fargo accepted a censure and agreed to pay a $650,000 fine and restitution to certain clients totaling $2,458,762.33 plus interest.

SEC SETTLEMENT On May 20, 2022, the SEC announced that Wells Fargo Clearing Services, LLC agreed to a settlement of allegations that, in connection with the firm’s failure to timely file certain SARS between April 2017 and October 2021, it willfully violated Section 17(A) of the Exchange Act and Rule 17A-8 thereunder. Without admitting or denying the findings contained in the order, with the exception of the SEC’s jurisdiction over it and the subject matter of the proceedings, the firm consented to: (a) cease and desist from committing or causing any violations and any future violations of Section 17(A) of the Exchange Act and Rule 17A-8 promulgated thereunder, (b) be censured, and (c) pay a civil monetary penalty in the amount of $7,000,000. The firm paid the civil monetary penalty on or about June 2, 2022.

NOTE: In addition to the above matters, certain of Wells Fargo & Company’s affiliates, including Wells Fargo Clearing Services, LLC (formerly Wells Fargo Advisors, LLC), Wells Fargo Securities, LLC, Wells Fargo Advisors Financial Network, LLC and First Clearing, LLC, have been involved in a number of civil proceedings and regulatory actions which concern matters arising in connection with the conduct of its business. Certain of such proceedings have resulted in findings of violations of federal or state securities laws. Such proceedings are reported and summarized in each entity’s Form BD as filed with the Securities and Exchange Commission and in other regulatory reports, which descriptions are hereby incorporated by reference.