Comerica (CMA) 424B5 Prospectus supplement for primary offering

Filed Pursuant to Rule 424(b)(5)
Registration No. 333-223083

The information in this preliminary prospectus supplement is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities and we are not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

Subject to completion, preliminary prospectus supplement dated July 26, 2018

Prospectus supplement

(To Prospectus dated February 16, 2018)

$                

Comerica Incorporated

$        Floating Rate Senior Notes due

$        % Senior Notes due

We are offering $                aggregate principal amount of our floating rate senior notes due                (the “floating rate notes”) and $                aggregate principal amount of our senior notes due                (the “fixed rate notes” and, together with the floating rate notes, the “notes”). The floating rate notes will bear interest at a floating rate equal to three-month LIBOR plus     % per annum, payable quarterly in arrears. The fixed rate notes will bear interest at the rate of     % per annum, payable semiannually in arrears.

We will pay interest on the floating rate notes on            ,            ,            and             of each year, beginning on            , 2018. We will pay interest on the fixed rate notes on                  and                  of each year, beginning on                  , 2019. The notes of each series will mature on                  ,             . The notes of each series are redeemable, in whole or in part, during the 30 days prior to the maturity date of the notes at 100% of the principal amount of the notes to be redeemed, plus accrued and unpaid interest to, but not including, the redemption date. See “Description of the notes—Optional redemption.”

The notes will be our unsecured and unsubordinated obligations and will rank equally among themselves and with all of our other unsecured and unsubordinated indebtedness from time to time outstanding. The notes will not be guaranteed by any of our subsidiaries.

The notes of each series will be issued only in registered book-entry form, in minimum denominations of $2,000 and integral multiples of $1,000 in excess thereof.

The notes are not deposits or other obligations of a bank or savings association and are not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.

Investing in the notes involves risks. See “Risk factors” beginning on pageS-10 to read about factors you should consider before buying the notes.

Neither the Securities and Exchange Commission nor any other regulatory body has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

	Per floating rate note		Total	Per fixed rate note		Total
Public offering price(1)		%	$		%	$
Underwriting discount		%	$		%	$
Proceeds to Comerica (before expenses)(1)		%	$		%	$

(1) Plus accrued and unpaid interest, if any, from                  , 2018 to the date of delivery.

The underwriters expect to deliver the notes of each series in book-entry form only through the facilities of The Depository Trust Company and its participants, including Clearstream Banking, S.A., and Euroclear Bank SA/NV, on or about                  , 2018, against payment in immediately available funds.

Joint Book-Running Managers

J.P. Morgan Morgan Stanley           RBC Capital Markets

Co-Manager

Comerica Securities

The date of this prospectus supplement is                  , 2018

You should rely only on the information contained or incorporated by reference in this prospectus supplement, the accompanying prospectus or any free writing prospectus we have authorized. We have not, and the underwriters have not, authorized anyone to provide you with information that is different. We are not, and the underwriters are not, making an offer to sell these securities in any jurisdiction where the offer or sale of these securities is not permitted. This prospectus supplement and the accompanying prospectus may only be used where it is legal to sell these securities. You should assume that the information in this prospectus supplement, the accompanying prospectus and any information we have incorporated herein and therein by reference is accurate only as of their respective dates. Our business, financial condition, results of operations and prospects may have changed since those respective dates.

Table of contents

	Page
Prospectus supplement
About this prospectus supplement		S-ii
Where you can find more information		S-ii
Cautionary statement regarding forward-looking statements		S-iv
Summary		S-1
Risk factors		S-10
Use of proceeds		S-14
Capitalization		S-15
Description of the notes		S-16
Certain United States federal income tax consequences		S-24
Certain ERISA considerations		S-28
Underwriting (Conflicts of interest)		S-30
Legal matters		S-35
Experts		S-35
Prospectus
About this prospectus		3
Forward-looking statements		3
Comerica Incorporated		4
Risk factors		4
Use of proceeds		5
Consolidated ratio of earnings to fixed charges		5
Description of capital stock		5
Description of depositary shares		9
Description of debt securities		12
Description of the warrants to purchase common stock or preferred stock		19
Description of the warrants to purchase debt securities		21
Description of stock purchase contracts and stock purchase units		22
Plan of distribution		22
ERISA considerations		24
Legal matters		26
Experts		26
Where you can find more information		26

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About this prospectus supplement

This document consists of two parts. The first part is this prospectus supplement, which describes the specific terms of this offering of the notes. The second part is the accompanying prospectus, which describes more general information, some of which may not apply to this offering. You should read both this prospectus supplement and the accompanying prospectus, together with the additional information described under the heading “Where you can find more information” below.

All references in this prospectus supplement to “Comerica,” “we,” “us,” “our” or similar references mean Comerica Incorporated and its successors, but does not include our consolidated subsidiaries except where the context otherwise so requires.

If the information set forth in this prospectus supplement differs in any way from the information set forth in the accompanying prospectus, you should rely on the information set forth in this prospectus supplement. If the information conflicts with any statement in a document which we have incorporated by reference, then you should only consider the statement in the more recent document.

Where you can find more information

We file annual, quarterly, and current reports, proxy statements, and other information with the Securities and Exchange Commission (the “SEC”). Our SEC filings are available to the public over the Internet at the SEC’s website at http://www.sec.gov and on the investor relations page of our website at http://www.comerica.com. Except for those SEC filings incorporated by reference in this prospectus supplement, none of the other information on our website is part of this prospectus supplement. You may also read and copy any document we file with the SEC at its public reference facilities at 100 F Street N.E., Washington, D.C. 20549. You can also obtain copies of the documents upon the payment of a duplicating fee to the SEC. Please call the SEC at1-800-SEC-0330 for further information on the operation of the public reference facilities.

The SEC’s rules allow us to “incorporate by reference” information into this prospectus supplement. This means that we can disclose important information to you by referring you to another document filed separately with the SEC. The information incorporated by reference is considered to be a part of this prospectus supplement. Any information incorporated by reference in this prospectus supplement that we file with the SEC after the date of this prospectus supplement will automatically update and supersede information contained in this prospectus supplement. Our SEC file number is001-10706.

We are incorporating by reference in this prospectus supplement the documents listed below and any future filings that we make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”) prior to the termination of this offering, excluding any portions of any such documents that are “furnished” but not “filed” for purposes of the Exchange Act:

• our Annual Report on Form10-K for the fiscal year ended December 31, 2017 (including the portions of our Proxy Statement on Schedule 14A, filed on March 13, 2018, incorporated by reference therein);

• our Quarterly Report on Form10-Q for the quarterly period ended March 31, 2018; and

• our Current Reports on Forms8-K filed on January 24, 2018, February 8, 2018, April 26, 2018 and July 24, 2018.

Upon written or oral request, we will provide—at no cost to the requester—a copy of any or all of the information that has been incorporated by reference in this prospectus supplement but not delivered with the

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prospectus supplement. You may request a copy of these filings, other than exhibits unless that exhibit is specifically incorporated by reference into that filing, at no cost, by writing or telephoning Comerica at the following address:

Investor Relations

Comerica Incorporated

Comerica Bank Tower

1717 Main Street

Dallas, Texas 75201

Telephone number:(214) 462-6831

You should rely only on the information incorporated by reference or provided in this prospectus supplement and the accompanying prospectus.

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Cautionary statement regarding forward-looking statements

This prospectus supplement, the accompanying prospectus and the documents incorporated by reference in this prospectus supplement and the accompanying prospectus include forward-looking statements as defined in the Private Securities Litigation Reform Act of 1995. Any statements in this report that are not historical facts are forward-looking statements as defined in the Private Securities Litigation Reform Act of 1995. Words such as “anticipates,” “believes,” “contemplates,” “feels,” “expects,” “estimates,” “seeks,” “strives,” “plans,” “intends,” “outlook,” “forecast,” “position,” “target,” “mission,” “assume,” “achievable,” “potential,” “strategy,” “goal,” “aspiration,” “opportunity,” “initiative,” “outcome,” “continue,” “remain,” “maintain,” “on track,” “trend,” “objective,” “looks forward,” “projects,” “models” and variations of such words and similar expressions, or future or conditional verbs such as “will,” “would,” “should,” “could,” “might,” “can,” “may” or similar expressions, as they relate to Comerica or its management, are intended to identify forward-looking statements. These forward-looking statements are predicated on the beliefs and assumptions of Comerica’s management based on information known to Comerica’s management as of the date such statements were made and do not purport to speak as of any other date. Forward-looking statements may include descriptions of plans and objectives of Comerica’s management for future or past operations, products or services, including the GEAR Up initiative, and forecasts of Comerica’s revenue, earnings or other measures of economic performance, including statements of profitability, business segments and subsidiaries as well as estimates of the economic benefits of the GEAR Up initiative, and estimates of credit trends and global stability. Such statements reflect the view of Comerica’s management as of this date with respect to future events and are subject to risks and uncertainties. Should one or more of these risks materialize or should underlying beliefs or assumptions prove incorrect, Comerica’s actual results could differ materially from those discussed. Factors that could cause or contribute to such differences are changes in general economic, political or industry conditions (which may include, among other items, changes in trade policies); changes in monetary and fiscal policies; whether Comerica may achieve opportunities for revenue enhancements and efficiency improvements under the GEAR Up initiative, or changes in the scope or assumptions underlying the GEAR Up initiative; operational difficulties, failure of technology infrastructure or information security incidents; reliance on other companies to provide certain key components of business infrastructure; Comerica’s ability to maintain adequate sources of funding and liquidity; the effects of more stringent capital or liquidity requirements; declines or other changes in the businesses or industries of Comerica’s customers; unfavorable developments concerning credit quality; changes in regulation or oversight; changes in the financial markets, including fluctuations in interest rates and their impact on deposit pricing; transitions away from LIBOR towards new interest rate benchmarks; reductions in Comerica’s credit rating; damage to Comerica’s reputation; Comerica’s ability to utilize technology to efficiently and effectively develop, market and deliver new products and services; competitive product and pricing pressures among financial institutions within Comerica’s markets; the interdependence of financial service companies; the implementation of Comerica’s strategies and business initiatives; changes in customer behavior due to factors including, but not limited to, fuel prices, energy costs, tariffs and real estate values; management’s ability to maintain and expand customer relationships; the effectiveness of methods of reducing risk exposures; the effects of catastrophic events including, but not limited to, hurricanes, tornadoes, earthquakes, fires, droughts and floods; the effects of recent tax reform and potential legislative, administrative or judicial changes or interpretations related to these and other tax regulations; any future strategic acquisitions or divestitures; management’s ability to retain key officers and employees; the impact of legal and regulatory proceedings or determinations; the effects of terrorist activities and other hostilities; changes in accounting standards; the critical nature of Comerica’s accounting policies and the volatility of Comerica’s stock price. Comerica cautions that the foregoing list of factors is notall-inclusive. For discussion of factors that may cause actual results to differ from expectations, please refer to Comerica’s filings with the SEC. In particular, please refer to “Item 1A. Risk Factors” beginning on page 11 of Comerica’s

S-iv

Annual Report on Form10-K for the year ended December 31, 2017. Forward-looking statements speak only as of the date they are made. Comerica does not undertake to update forward-looking statements to reflect facts, circumstances, assumptions or events that occur after the date the forward-looking statements are made, except as required by law. For any forward-looking statements made in this prospectus supplement, the accompanying prospectus or the documents incorporated by reference, Comerica claims the protection of the safe harbor for forward-looking statements contained in the Private Securities Litigation Reform Act of 1995.

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Summary

The following summary should be read together with the information contained in other parts of this prospectus supplement and the accompanying prospectus, including the documents we incorporate by reference. This summary highlights selected information from this prospectus supplement, the accompanying prospectus and the documents incorporated by reference to help you understand the offering of the notes. You should read this prospectus supplement and the accompanying prospectus carefully to understand fully the terms of the notes as well as the other considerations that are important to you in making a decision about whether to invest in the notes. You should pay special attention to the “Risk factors” section beginning on pageS-10 of this prospectus supplement and the information set forth under the caption “Risk Factors” in our Annual Report on Form10-K for the year ended December 31, 2017 and the other documents, we incorporate by reference, before you determine whether an investment in the notes is appropriate for you.

About Comerica Incorporated

Comerica is a financial services company incorporated under the laws of the State of Delaware and headquartered in Dallas, Texas. Based on total assets, as of March 31, 2018, it was among the 25 largest commercial financial holding companies in the United States. As of March 31, 2018, Comerica owned directly or indirectly all the outstanding common stock of two active banking subsidiaries and 33 nonbanking subsidiaries. At March 31, 2018, Comerica had total assets of approximately $72.3 billion, total deposits of approximately $57.6 billion, total loans of approximately $49.2 billion and shareholders’ equity of approximately $8.0 billion.

Comerica has strategically aligned its operations into three major business segments: the Business Bank, the Retail Bank, and Wealth Management. In addition to the three major business segments, Finance is also reported as a segment.

• The Business Bank meets the needs of middle market businesses, multinational corporations and governmental entities by offering various products and services, including commercial loans and lines of credit, deposits, cash management, capital market products, international trade finance, letters of credit, foreign exchange management services and loan syndication services.

• The Retail Bank includes small business banking and personal financial services, consisting of consumer lending, consumer deposit gathering and mortgage loan origination. In addition to a full range of financial services provided to small business customers, this business segment offers a variety of consumer products, including deposit accounts, installment loans, credit cards, student loans, home equity lines of credit and residential mortgage loans.

• Wealth Management offers products and services consisting of fiduciary services, private banking, retirement services, investment management and advisory services, investment banking and brokerage services. This business segment also offers the sale of annuity products, as well as life, disability and long-term care insurance products.

• Finance includes Comerica’s securities portfolio and asset and liability management activities. This segment is responsible for managing Comerica’s funding, liquidity and capital needs, performing interest sensitivity analysis and executing various strategies to manage Comerica’s exposure to liquidity, interest rate risk and foreign exchange risk.

Comerica operates in three primary geographic markets—Texas, California, and Michigan, as well as in Arizona and Florida, with select businesses operating in several other states, and in Canada and Mexico.

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Comerica has two active banking subsidiaries, Comerica Bank and Comerica Bank & Trust, National Association. Comerica has consolidated most of its banking business into Comerica Bank, which is chartered by the State of Texas, and at the state level is supervised and regulated by the Texas Department of Banking. Comerica Bank is a member of the Federal Reserve System and supervised and regulated by the Federal Reserve Bank of Dallas, and has branches in Texas, Michigan, California, Florida and Arizona. Comerica Bank & Trust, National Association is chartered under federal law and is subject to supervision and regulation by the Office of the Comptroller of the Currency. Comerica Bank & Trust, National Association is also a member of the Federal Reserve System. The deposits of Comerica Bank and Comerica Bank & Trust, National Association are insured by the Deposit Insurance Fund of the FDIC to the extent provided by law. Comerica is a bank holding company under the Bank Holding Company Act of 1956, as amended, and has elected to become a financial holding company under the provisions of the Gramm-Leach-Bliley Act. Accordingly, Comerica is subject to supervision and regulation at the federal level by the Board of Governors of the Federal Reserve System.

Comerica’s principal executive office is located at Comerica Bank Tower, 1717 Main Street, Dallas, Texas 75201, and its telephone number is(214) 462-6831.

Recent developments

Unaudited financial results as of and for the quarter ended June 30, 2018

On July 17, 2018, Comerica announced its unaudited financial results for the three and six months ended June 30, 2018 that included the information set forth below.

Comerica reported second quarter 2018 net income of $326 million, or $1.87 per share, compared to $281 million, or $1.59 per share, for the first quarter 2018.

Average total loans increased $804 million, compared to the first quarter 2018, to $49.2 billion in the second quarter 2018, primarily reflecting seasonal increases in Mortgage Banker Finance and National Dealer Services as well as growth in Technology and Life Sciences (mainly Equity Fund Services) and general Middle Market. Loan yields increased 37 basis points to 4.63 percent reflecting an increase in short term rates, higher interest recoveries and other dynamics.

Average total deposits decreased $260 million, compared to the first quarter 2018, to $55.8 billion in the second quarter 2018, driven by a $553 million decrease in noninterest-bearing deposits, which was partially offset by a $293 million increase in interest-bearing deposits. This decrease primarily reflected a decrease in general Middle Market, driven by seasonality in Municipalities, which was mostly offset by increases in other lines of business. Interest-bearing deposit costs increased 17 basis points to 0.42 percent as deposit rates were prudently increased with the faster pace of LIBOR rising.

Net interest income increased $41 million, compared to the first quarter 2018, to $590 million in the second quarter 2018, primarily due to a net benefit from higher short-term rates, an increase in average loans, higher interest recoveries and one additional day in the second quarter. Net interest margin increased 21 basis points from the first quarter to 3.62 percent.

The provision for credit losses decreased $41 million, compared to the first quarter 2018, to a benefit of $29 million in the second quarter 2018, reflecting a decline in total criticized loans of $355 million, or 17 percent, and net credit-related recoveries of $3 million.

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Noninterest income increased $4 million from the first quarter 2018, primarily reflecting an increase of $5 million in commercial lending fees, mostly due to an increase in syndication fees, which was partially offset by a $2 million charge related to a derivative contract tied to the conversion rate of Visa Class B shares.

Noninterest expenses increased $2 million from the first quarter 2018. Excluding the impact of a $5 million business tax refund in the first quarter 2018, noninterest expenses decreased $3 million, primarily reflecting decreases of $5 million each in salaries and benefits expense and restructuring charges, which was partially offset by increases of $3 million and $2 million in outside processing expense and advertising expense, respectively. The decrease in salaries and benefits expense primarily reflected seasonal decreases in share-based compensation and payroll taxes, which was partially offset by the impact of higher incentive compensation tied to financial performance, merit increases, an increase in staff insurance and one additional day in the quarter.

Compared to the first quarter 2018, the provision for income taxes increased $39 million to $93 million, due to the tax impact from the $84 million increase inpre-tax earnings and a $16 million decrease in tax benefits from employee stock transactions.

In the second quarter 2018, Comerica returned $227 million to shareholders, including dividends and the repurchase of $169 million of common stock (1.8 million shares) under the equity repurchase program.

The second quarter results included above are preliminary and unaudited and may be revised as a result of management’s further review of our results. During the course of the preparation of our unaudited consolidated quarterly financial statements and related notes, we may identify items that would require us to make adjustments to the financial information presented above.

Capital actions announcement

On July 24, 2018, the Board of Directors of Comerica (the “Board”) approved capital actions aimed at increasing shareholder returns while continuing to appropriately manage its capital base as well as support growth and investment in its business. The Board also approved a 26-cent increase in the quarterly dividend to $0.60 per share, effective for the dividend payable October 1, 2018, as well as the repurchase of $500 million of outstanding common stock during third quarter 2018.

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The offering

The following summary contains basic information about the notes and is not intended to be complete. It may not contain all the information that is important to you. For a more complete description of the notes, you should read the section of this prospectus supplement entitled “Description of the notes” and the section in the accompanying prospectus entitled “Description of debt securities.”

Issuer Comerica Incorporated, a Delaware corporation.

Securities offered $             aggregate principal amount of floating rate senior notes due              $             aggregate principal amount of     % senior notes due             .

Issue date                 , 2018.

Maturity Each of the floating rate notes and the fixed rate notes will mature on             ,             .

Interest Rates The floating rate notes will bear interest from                 , 2018 at a floating rate equal to three-month LIBOR plus     % per annum, payable in cash quarterly in arrears.

The fixed rate notes will bear interest from                 , 2018 at the rate of     % per annum, payable in cash semiannually in arrears.

Interest We will pay interest on the floating rate notes on                 ,                 ,                 and                 of each year, beginning on                 , 2018 and we will pay interest on the fixed rate notes                 on                 and                 of each year, beginning on                 , 2019.

Ranking The notes will be our unsecured and unsubordinated obligations and will rank:

• senior in right of payment to any of our existing and future indebtedness that is expressly subordinated in right of payment to the notes;

• equal in right of payment to our existing and future unsecured indebtedness that is not so subordinated;

• effectively subordinated to any secured indebtedness, to the extent of the value of the assets securing such indebtedness; and

• structurally subordinated to all existing and future liabilities, including claims with respect to deposit liabilities and trade payables, of our subsidiaries.

As of March 31, 2018, our subsidiaries had, in the aggregate, outstanding debt and other liabilities, including deposits, of approximately $64.6 billion. All of such debt and other liabilities would rank structurally senior to the notes in case of liquidation or otherwise. As of March 31, 2018, Comerica Incorporated (parent company only) had an aggregate of approximately $346 million of outstanding senior debt, all of which would be equal in right of payment with the notes, approximately $248 million of outstanding subordinated debt and no secured debt.

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The indenture does not limit the amount of additional indebtedness we or our subsidiaries may incur.

Optional Redemption At any time on and after             ,             (30 days prior to the maturity date of the notes), we may redeem some or all of the notes of either series at our option, at a redemption price equal to 100% of the principal amount of the notes being redeemed plus accrued and unpaid interest on the notes being redeemed to, but not including, the redemption date. See “Description of the notes — Optional redemption.”

No guarantees The notes are not guaranteed by any of our subsidiaries. As a result, the notes will be structurally subordinated to the indebtedness and other liabilities of our subsidiaries as discussed above under “Ranking.”

Further issuances We may from time to time, without notice to or the consent of the holders of notes of a series, create and issue additional debt securities having the same terms (other than the original issuance date and, in some cases, the public offering price, the initial interest accrual date and the initial interest payment date) as and ranking equally and ratably with the notes of the corresponding series offered by this prospectus supplement. If issued, any additional debt securities will become part of the same series as the corresponding series of notes offered by this prospectus supplement.

Use of proceeds We intend to use the proceeds for general corporate purposes, which may include working capital, investments in or advances to our existing or future subsidiaries, and repurchases, maturities and redemptions of our other outstanding securities, including the recently announced repurchase of our common stock. Pending such use, we intend to use the net proceeds to make short-term investments. See the section entitled “Use of proceeds.”

Listing The notes will not be listed on any securities exchange.

Denomination and form We will issue each series of the notes in the form of one or more fully registered global notes registered in the name of the nominee of The Depository Trust Company (“DTC”). Beneficial interests in the notes will be represented through book-entry accounts of financial institutions acting on behalf of beneficial owners as direct and indirect participants in DTC. Clearstream Banking, S.A. and Euroclear Bank SA/NV, will hold interests on behalf of their participants through their respective U.S. depositaries, which in turn will hold such interests in accounts as participants of DTC. Except in the limited circumstances described in this prospectus supplement, owners of beneficial interests in the notes will not be entitled to have notes registered in their names, will not receive or be entitled to receive notes in definitive form and will not be considered holders of notes under the indenture. The notes of each series will be issued only in denominations of $2,000 and integral multiples of $1,000 in excess thereof.

Conflicts of interest Comerica Securities, Inc., one of the underwriters in this offering, is our affiliate. The distribution arrangements for this offering comply with the requirements of Financial Industry Regulatory Authority, Inc. (“FINRA”) Rule 5121, regarding a FINRA member firm’s participation in the distribution of securities of an affiliate.

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In accordance with Rule 5121, no FINRA member firm that has a conflict of interest under Rule 5121 may make sales in this offering to any discretionary account without the prior approval of the customer.

Governing law The indenture and the notes are governed by and will be construed in accordance with the laws of the State of New York.

Trustee and Calculation Agent The Bank of New York Mellon Trust Company, N.A. will act as trustee for the notes. The Bank of New York Mellon Trust Company, N.A. will also act as calculation agent for the floating rate notes, until such time as we appoint a successor calculation agent.

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Summary consolidated financial information

The following table presents summary consolidated financial and other data as of and for the periods presented. The summary financial data as of December 31, 2017 and 2016 and for each of the years in the three-year period ended December 31, 2017 are derived from our audited consolidated financial statements and related notes, which are incorporated by reference into this prospectus supplement and the accompanying prospectus. The summary financial data for prior years is derived from our audited consolidated financial statements which are not incorporated by reference into this prospectus supplement and accompanying prospectus. The summary financial data as of March 31, 2018 and 2017 and for the three-month periods ended March 31, 2018 and 2017 are derived from our unaudited consolidated financial statements and related notes, which are incorporated by reference into this prospectus supplement and the accompanying prospectus. Such unaudited financial statements have been prepared on the same basis as our annual consolidated financial statements and include all adjustments, consisting of only normal recurring adjustments, necessary for the fair presentation of the data in all material respects. The results for any interim period are not necessarily indicative of the results of operations to be expected for a full fiscal year.

	As of or for  the three months ended March 31,				As of or for the year ended December 31,
	2018		2017		2017		2016		2015		2014		2013
	(in millions)
Income statement data:
Net interest income	$	549	$	470	$	2,061	$	1,797	$	1,689	$	1,655	$	1,672
Provision for loan losses		12		16		74		248		147		27		46
Noninterest income		244		271		1,107		1,051		1,035		857		874
Noninterest expenses		446		457		1,860		1,930		1,827		1,615		1,714
Income (loss) from continuing operations before income taxes		335		268		1,234		670		750		870		786
Provision (benefit) for income taxes		54		66		491		193		229		277		245
Net income from continuing operation		281		202		743		477		521		593		541
Income from discontinued operations, net of tax		0		0		0		0		0		0		0
Net income		281		202		743		477		521		593		541
Preferred stock dividends		0		0		0		0		0		0		0
Income allocated to participating securities		2		2		5		4		6		7		8
Net income (loss) attributable to common shares	$	279	$	200	$	738	$	473	$	515	$	586	$	533

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	As of or for  the three months ended March 31,				As of or for the year ended December 31,
	2018		2017		2017		2016		2015		2014		2013
	(in millions)
Balance sheet data:
Total assets	$	72,335	$	72,976	$	71,567	$	72,978	$	71,877	$	69,186	$	65,224
Total investment securities		11,971		12,338		12,204		12,369		12,500		10,051		9,307
Total loans		49,240		48,303		49,173		49,088		49,084		48,593		45,470
Total earning assets		67,007		67,876		65,880		67,518		66,687		63,788		60,200
Total deposits		57,635		58,863		57,903		58,985		59,853		57,486		53,292
Total medium- and long-term debt		5,594		5,153		4,622		5,160		3,058		2,675		3,543
Total common shareholders’ equity		8,000		7,930		7,963		7,796		7,560		7,402		7,150
Total shareholders’ equity		8,000		7,930		7,963		7,796		7,560		7,402		7,150
Average Balances:
Total assets	$	70,326	$	71,819	$	71,452	$	71,743	$	70,247	$	66,336	$	63,933
Total investment securities		11,911		12,198		12,207		12,348		10,237		9,350		9,637
Total loans		48,421		47,900		48,558		48,996		48,628		46,588		44,412
Total earning assets		65,012		66,648		66,300		66,545		65,129		61,560		59,091
Total deposits		56,090		57,779		57,258		57,741		58,326		54,784		51,711
Total medium- and long-term debt		5,192		5,157		4,969		4,917		2,905		2,963		3,972
Total common shareholders’ equity		7,927		7,865		7,952		7,674		7,534		7,373		6,965
Total shareholders’ equity		7,927		7,865		7,952		7,674		7,534		7,373		6,965

	As of or for the three months ended March 31,				As of or for the year ended December 31,
	2018		2017		2017		2016		2015		2014		2013
	(dollars in millions)
Credit Quality:
Total allowance for credit losses	$	738	$	754	$	754	$	771	$	679	$	635	$	634
Total nonperforming loans		334		529		410		590		379		290		374
Foreclosed property		5		16		5		17		12		10		9
Total nonperforming assets		339		545		415		607		391		300		383
Net credit-related charge-offs		28		33		92		157		101		25		73
Nonperforming assets as a percentage of total loans and foreclosed property		0.69%		1.13%		0.84%		1.24%		0.80%		0.62%		0.84%
Net credit-related charge-offs as a percentage of average total loans		0.23		0.28		0.19		0.32		0.21		0.05		0.16
Allowance for loan losses as a percentage of totalperiod-end loans		1.42		1.47		1.45		1.49		1.29		1.22		1.32
Allowance for loan losses as a percentage of total nonperforming loans		209		134		173		124		167		205		160

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	As of or for the three months ended March 31,				As of or for the year ended December 31,
	2018		2017		2017		2016		2015		2014		2013
Ratios:
Net interest margin		3.41%		2.85%		3.12%		2.71%		2.60%		2.70%		2.84%
Return on average assets		1.62		1.14		1.04		0.67		0.74		0.89		0.85
Return on average common shareholders’ equity		14.37		10.42		9.34		6.22		6.91		8.05		7.76
Dividend payout ratio		18.52		20.00		25.77		32.48		28.33		24.09		23.29
Average common shareholders’ equity as a percentage of average assets		11.06		10.87		11.13		10.70		10.73		11.11		10.90
Tier 1 common capital as a percentage of risk-weighted assets		11.98		11.55		11.68		11.09		10.54		N/M		N/M
Tier 1 capital as a percentage of risk-weighted assets		11.98		11.55		11.68		11.09		10.54		10.50		10.64
Tangible common equity as a percentage of tangible assets		10.26		10.07		10.32		9.89		9.70		9.85		10.07
Ratio of earnings to fixed charges(a):
Excluding interest on deposits		11.75x		12.90x		13.03x		7.94x		10.87x		12.42x		10.73x
Including interest in deposits		8.06x		9.38x		9.53x		5.94x		7.31x		8.21x		6.81x

N/M—Not Meaningful

(a) For purposes of computing this ratio, earnings represent income before income taxes and fixed charges, and after interest and penalties on tax liabilities. Fixed charges include interest, whether expensed or capitalized, and that portion of rental expense deemed representative of the interest factor.

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Risk factors

Investing in the notes involves risks, including the risks described below that are specific to the notes and those that could affect us and our business. You should not purchase notes unless you understand these investment risks. Please be aware that other risks may prove to be important in the future. New risks may emerge at any time, and we cannot predict such risks or estimate the extent to which they may affect our financial performance. Before purchasing any notes, you should carefully consider the following discussion of risks and the other information in this prospectus supplement and the accompanying prospectus, and carefully read the risks described in the documents, we incorporate by reference in this prospectus supplement, including those set forth under the caption “Risk Factors” in our Annual Report on Form10-K for the year ended December 31, 2017.

The notes are our obligations and not obligations of our subsidiaries and will be structurally subordinated to the claims of our subsidiaries’ creditors.

The notes are exclusively our obligations and not those of our subsidiaries. We are a holding company that conducts substantially all of our operations through our bank andnon-bank subsidiaries. As a result, our ability to make payments on the notes will depend primarily upon the receipt of dividends and other distributions from our subsidiaries. If we do not receive sufficient cash dividends and other distributions from our subsidiaries, it is unlikely that we will have sufficient funds to make payments on the notes.

Our subsidiaries are separate and distinct legal entities. Our subsidiaries have no obligation to pay any amounts due on the notes or to provide us with funds to pay our obligations, whether by dividends, distributions, loans or other payments. In addition, any dividend payments, distributions, loans or advances to us by our subsidiaries in the future will require the generation of future earnings by our subsidiaries and may require regulatory approval. Regulations of both the Board of Governors of the Federal Reserve System and the Texas Department of Banking affect the ability of Comerica Bank to pay dividends and other distributions to us and to make loans to us. If Comerica Bank is unable to make dividend payments to us and sufficient capital is not otherwise available, we may not be able to make principal and interest payments on our debt, including the notes.

In addition, our right to participate in any distribution of assets of any of our subsidiaries upon the subsidiary’s liquidation or otherwise, and thus your ability as a holder of the notes to benefit indirectly from such distribution, will be subject to the prior claims of creditors of that subsidiary (including, in the case of Comerica Bank, its depositors), except to the extent that we are a creditor of such subsidiary with claims that are recognized. As a result, the notes effectively will be subordinated to all existing and future liabilities and obligations of our subsidiaries, including deposit liabilities. At March 31, 2018, the aggregate amount of all debt and other liabilities of our consolidated subsidiaries, including deposits, that would structurally rank senior to the notes was approximately $64.6 billion. Our subsidiaries may incur additional debt and liabilities in the future, all of which would rank structurally senior to the notes.

The notes will be effectively subordinated to all of our secured indebtedness.

The notes will be effectively subordinated to any secured debt that we may have from time to time, to the extent of the value of the assets securing such debt. In the event that we are declared bankrupt, become insolvent or are liquidated or reorganized, any assets that secure other debt will be available to pay obligations on the notes only after the secured debt has been paid in full. Holders of the notes will participate ratably with all holders of our unsecured indebtedness that is deemed to be of the same ranking as the notes, and potentially with all of our other general creditors, based upon the respective amounts owed to each holder or creditor, in our remaining assets. In any of the foregoing events, we may not have sufficient assets to pay amounts due on the notes. As a result, if holders of the notes receive any payments, they may receive less, ratably, than holders of secured indebtedness. At March 31, 2018, Comerica Incorporated (parent company only) had no secured debt.

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There are limited covenants in the indenture.

Neither we nor any of our subsidiaries is restricted from incurring additional debt or other liabilities, including additional senior debt, under the indenture. If we incur additional debt or liabilities, our ability to pay our obligations on the notes could be adversely affected. We expect to incur, from time to time, additional debt and other liabilities. In addition, we are not restricted under the indenture from granting security interests over our assets, or from paying dividends or issuing or repurchasing our securities.

In addition, the indenture and the notes do not contain, among other things, provisions which would afford holders of the notes protection in the event of a recapitalization transaction, a change of control of Comerica or a highly leveraged transaction involving Comerica which could adversely affect the holders of the notes, except to the extent described under “Description of debt securities—Consolidations, mergers and sales of assets” included in the accompanying prospectus.

The notes are not insured or guaranteed by the FDIC.

The notes are not deposits or other obligations of a bank or savings association and are not insured or guaranteed by the FDIC or any other governmental agency.

You may be unable to sell the notes because there is no public trading market for the notes.

The notes of each series are a new issue of securities with no established trading market. The notes will not be listed on any securities exchange or included in any automated quotation system. Consequently, the notes will be relatively illiquid and you may be unable to sell your notes. Although the representatives of the underwriters have advised us that, following completion of the offering of the notes, one or more of the underwriters currently intend to make a secondary market in the notes of each series, they are not obligated to do so and may discontinue any market-making activities at any time without notice. Accordingly, a trading market for the notes may not develop or any such market may not have sufficient liquidity.

If a trading market for the notes develops, changes in our credit ratings or the debt markets could adversely affect the liquidity and market price of the notes.

If a trading market develops, the liquidity and prices of the notes will depend on many factors, including: (i) our credit ratings with major credit rating agencies; (ii) the prevailing interest rates being paid by other companies similar to us; (iii) our financial condition, financial performance and future prospects; and (iv) the overall condition of the financial markets.

The condition of the financial markets and prevailing interest rates have fluctuated significantly in the past and may fluctuate in the future. Such fluctuations could have an adverse effect on the liquidity and price of the notes.

In addition, credit rating agencies periodically review their ratings and ratings methodologies for the companies that they follow, including us. A negative change in ratings or outlook could have an adverse effect on the liquidity and price of the notes.

A credit rating is not a recommendation to buy, sell or hold securities and may be revised, suspended or withdrawn by the credit rating agency at any time.

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The price at which you will be able to sell your notes prior to maturity will depend on a number of factors and may be substantially less than the amount you originally invest.

We believe that the value of the notes in any secondary market will be affected by the supply and demand of the notes, prevailing interest rates and a number of other factors. Some of these factors are interrelated in complex ways. As a result, the effect of any one factor may be offset or magnified by the effect of another factor. The following paragraphs describe what we expect to be the impact on the market value of the notes of a change in a specific factor, assuming all other conditions remain constant.

United States interest rates.    We expect that the market value of the notes will be affected by changes in United States interest rates. In general, if United States interest rates increase, the market value of the notes may decrease.

Our credit rating, financial condition and results.    Actual or anticipated changes in our credit ratings or financial condition may affect the market value of the notes. In general, if our credit ratings or financial condition change adversely, the market value of the notes may decrease.

We want you to understand that the impact of one of the factors above, such as an increase in United States interest rates, may offset some or all of any change in the market value of the notes attributable to another factor, such as an improvement in our credit rating.

Our credit ratings are reviewed periodically and we could be subject to downgrades in the future.

Our credit ratings are an important factor in determining the cost and availability of short- and long-term funding, as well as collateral requirements for certain derivative instruments. In general, rating agencies base their ratings on many quantitative and qualitative factors, including capital adequacy, liquidity, asset quality, business mix and level and quality of earnings and the current legislative and regulatory environment, including implied government support, and there can be no assurance that we will maintain our current credit ratings. There can be no assurance that such changes will not affect ratings of our securities or of securities in which we have an economic interest. Any decrease, or potential decrease, in credit ratings could impact access to the capital markets and/or increase the cost of debt, and thereby adversely affect liquidity and financial condition.

Our credit ratings may not reflect all risks of an investment in the notes.

The credit ratings assigned to the notes may not reflect the potential impact of all risks related to structure and other factors on any trading market, if any, for, or trading value of, your notes. In addition, real or anticipated changes in our credit ratings will generally affect any trading market, if any, for, or trading value of, your notes. Accordingly, you should consult your own financial and legal advisors as to the risks entailed by an investment in the notes and the suitability of investing in the notes in light of your particular circumstances.

The amount of interest payable on the floating rate notes is set only once per interest period based on the applicable LIBOR determination date, which rate is based on the three-month LIBOR and may fluctuate substantially.

In the past, the level of three-month LIBOR has experienced significant fluctuations. You should note that historical levels, fluctuations and trends of three-month LIBOR are not necessarily indicative of future levels, fluctuations and trends. Any historical upward or downward trend in three-month LIBOR is not an indication that three-month LIBOR is more or less likely to increase or decrease during the life of the floating rate notes, and you should not take the historical levels of three-month LIBOR rate as an indication of its future

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performance. You should further note that although the actual three-month LIBOR on an interest payment date or at other times during an interest period may be higher than the three-month LIBOR on the applicable LIBOR determination date (as defined herein) for the floating rate notes, you will not benefit from the three-month LIBOR at any time other than on the interest rate determination for such period. As a result, changes in the three-month LIBOR may not result in a comparable change in the market value of the floating rate notes.

Changes in banks’ inter-bank lending rate reporting practices or the method pursuant to which LIBOR is determined may adversely affect the value of the floating rate notes.

LIBOR and other indices which are deemed “benchmarks” are the subject of recent national, international, and other regulatory guidance and proposals for reform. Some of these reforms are already effective while others are still to be implemented. These reforms may cause such benchmarks to perform differently than in the past, or have other consequences which cannot be predicted. In particular, regulators and law enforcement agencies in the U.K. and elsewhere are conducting criminal and civil investigations into whether the banks that contribute information to the British Bankers’ Association (the “BBA”) in connection with the daily calculation of LIBOR may have been under-reporting or otherwise manipulating or attempting to manipulate LIBOR. A number of BBA member banks have entered into settlements with their regulators and law enforcement agencies with respect to this alleged manipulation of LIBOR. Actions by the regulators or law enforcement agencies, as well as ICE Benchmark Administration (the current administrator of LIBOR), may result in changes to the manner in which LIBOR is determined or the establishment of alternative reference rates. For example, on July 27, 2017, the U.K. Financial Conduct Authority announced that it intends to stop persuading or compelling banks to submit LIBOR rates after 2021.

At this time, it is not possible to predict the effect of any such changes, any establishment of alternative reference rates or any other reforms to LIBOR that may be implemented in the U.K. or elsewhere. Uncertainty as to the nature of such potential changes, alternative reference rates or other reforms may adversely affect the trading market for securities the interest or dividend on which is determined by reference to LIBOR, such as the floating rate notes. To the extent the three-month LIBOR rate is discontinued or is no longer quoted, the applicable base rate used to calculate interest payments on the floating rate notes will be determined using the alternative methods described in “Description of the notes—Payments—Floating rate notes.” Any of these alternative methods may result in interest payments that are lower than or that do not otherwise correlate over time with the interest payments that would have been made on the floating rate notes if the three-month LIBOR rate was available in its current form. The final alternative method sets the interest rate at the same rate as the immediately preceding interest period. In the event market interest rates rise thereafter, the floating rate notes would bear a fixed rate and could decline in value because the premium, if any, over market interest rates will decline.

More generally, any of the above changes or any other consequential changes to LIBOR or any other “benchmark” as a result of international, national, or other proposals for reform or other initiatives or investigations, or any further uncertainty in relation to the timing and manner of implementation of such changes, could have a material adverse effect on the value of and return on any securities based on or linked to a “benchmark,” such as the floating rate notes.

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Use of proceeds

We expect to receive net proceeds from this offering of approximately $             million after deducting the underwriting discounts and expenses payable by us. We intend to use the net proceeds for general corporate purposes, which may include working capital, investments in or advances to our existing or future subsidiaries, and repurchases, maturities and redemptions of our other outstanding securities, including the recently announced repurchase of our common stock. See “Summary—Recent developments—Capital actions announcement.” Pending such use, we intend to use the net proceeds to make short-term investments.

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Capitalization

The following table sets forth our consolidated capitalization as of March 31, 2018, on an actual basis and as adjusted to give effect to the issuance of the notes offered hereby. The table should be read in conjunction with the consolidated financial statements incorporated herein by reference.

	As of March 31, 2018
	Actual			As adjusted
	(dollars in millions)
Medium- and long-term debt
Floating rate notes offered hereby	$	—		$
Fixed rate notes offered hereby		—
Other medium- and long-term debt		5,594
Total medium and long-term debt		5,594
Equity
Common stock, $5 par value		1,141
Capital surplus		2,134
Accumulated other comprehensive income (loss)		(553	)
Retained earnings		8,110
Less cost of common stock in treasury		(2,832	)
Total equity		8,000
Total capitalization	$	13,594		$

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Description of the notes

Each series of the notes will be issued as a separate series under the indenture dated as of May 23, 2014, between us and The Bank of New York Mellon Trust Company, N.A., as trustee (the “trustee”). The terms of the notes include those expressly set forth in the indenture and those incorporated into the indenture pursuant to the Trust Indenture Act of 1939, as amended. We urge you to read the indenture because it, and not this description, defines your rights as a holder of the notes. The following describes the general terms and provisions of the notes. The accompanying prospectus provides a more complete description of the indenture. The notes will be senior debt securities, as such term is used in the accompanying prospectus. The following description of the particular terms of the notes supplements, and to the extent inconsistent therewith replaces, the description of the general terms and provisions of the senior debt securities in the accompanying prospectus, to which reference is made. These descriptions are not complete, and are qualified in their entirety by reference to, all the provisions of the indenture.

References to “Comerica,” “the Company,” “we,” “us” and “our” in this section are only to Comerica Incorporated and not to its subsidiaries.

General

The notes will be unsecured obligations of Comerica and will rank equally with all of our other existing and future unsecured and unsubordinated indebtedness. The notes will rank senior in right of payment to our subordinated indebtedness. The notes will not be guaranteed by any of our subsidiaries. The notes are not deposits or other obligations of a bank or savings association and are not insured or guaranteed by the FDIC or any other governmental agency. The notes will be effectively subordinated to any secured indebtedness, to the extent of the value securing such indebtedness. The fixed rate notes and the floating rate notes will be separate series of notes.

We are a holding company, and most of our revenues result from dividends from our bank subsidiaries. As a result, our ability to make payments on the notes will depend primarily upon the receipt of dividends and other distributions from our subsidiaries. There are various regulatory restrictions on the ability of Comerica Bank to pay dividends or make other payments to us. See “Item 1—Supervision and Regulation—Dividends” in our Annual Report on Form10-K for the year ended December 31, 2017.

In addition, our subsidiaries are legal entities separate and distinct from the Company. Our subsidiaries may, without notice or consent of the holders of the notes, incur additional debt and liabilities in the future, all of which would rank structurally senior to the notes. Our right to participate in any distribution of assets of any of our subsidiaries upon the subsidiary’s liquidation or otherwise, and thus your ability as a holder of the notes to benefit indirectly from such distribution, will be subject to the prior claims of creditors of that subsidiary (including, in the case of our bank subsidiaries, their depositors), except to the extent that we are a creditor of such subsidiary with claims that are recognized. As a result, the notes effectively will be subordinated to all existing and future liabilities and obligations of our subsidiaries, including deposit liabilities and trade payables. As of March 31, 2018, our subsidiaries had, in the aggregate, outstanding debt and other liabilities, including deposits, of approximately $64.6 billion. All of such debt and other liabilities would rank structurally senior to the notes in case of liquidation or otherwise. As of March 31, 2018, Comerica Incorporated (parent company only) had an aggregate of approximately $346 million of outstanding senior debt and approximately $248 million of outstanding subordinated debt and no secured debt.

The indenture does not limit the amount of notes, debentures or other evidences of indebtedness that we may issue under the indenture or otherwise and provides that notes, debentures or other evidences of indebtedness may be issued from time to time in one or more series. We may from time to time, without giving notice to or seeking the consent of the holders of the notes of a series, issue notes having the same ranking and the same interest rate, maturity and other terms as the notes of such series issued in this offering (other than the original

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issuance date and, in some cases, the public offering price, the initial interest accrual date and the initial interest payment date). Any additional securities having such similar terms, together with the corresponding series of notes, may constitute a single series of securities under the indenture.

Principal and interest will be payable, and the notes will be transferable or exchangeable, at the office or offices or agency maintained by us for these purposes. Payment of interest on the notes may be made at our option by check mailed to the registered holders.

The notes of each series will be issued only in fully registered form without coupons and in denominations of $2,000 or any whole multiple of $1,000 in excess thereof. No service charge will be made for any transfer or exchange of the notes, but we may require payment of a sum sufficient to cover any tax or other governmental charge payable in connection with a transfer or exchange.

The notes of each series will be represented by one or more global securities registered in the name of a nominee of DTC. Except as described below under “Description of the notes—Book-entry; delivery and form,” the notes will not be issuable in certificated form.

The notes are subject to the defeasance provisions explained in the accompanying prospectus under “Description of debt securities—Discharge, Defeasance and Covenant Defeasance.”

The notes will not be convertible into Comerica common or preferred stock or exchangeable for any other securities, whether or not issued by Comerica.

When we use the term “business day,” we mean any day except a Saturday, a Sunday or a day in the City of New York on which banking institutions are authorized or obligated by law or executive order to close.

Payments

Floating rate notes

The floating rate notes will bear interest for each interest period at a rate determined by the calculation agent. The calculation agent is The Bank of New York Mellon Trust Company, N.A. until such time as we appoint a successor calculation agent. Interest on the floating rate notes will accrue from and including                 , 2018 and will be payable in arrears quarterly on                ,                ,                 , and                of each year, commencing on                 , 2018. The interest payable on the floating rate notes on any interest payment date, subject to certain exceptions, will be paid to the person in whose name the floating rate notes are registered at the close of business on the 15th business day preceding the next interest payment date. Interest on the floating rate notes will be computed on the basis of the actual number of days in an interest period and a360-day year.

If an interest payment date or the maturity date for the floating rate notes falls on a day that is not a business day, Comerica will postpone the interest payment date to the next succeeding business day unless such next succeeding business day would be in the following month, in which case, the interest payment date shall be the immediately preceding business day, but the payments made on such dates will be treated as being made on the date that the payment was first due and the holders of the floating rate notes will not be entitled to any further interest or other payments with respect to such postponements. Interest on the floating rate notes will be paid to but excluding the relevant interest payment date.

The interest rate on the floating rate notes for a particular interest period will be a per annum rate equal to three-month LIBOR as determined on the interest determination date plus    %. The interest determination date for an interest period will be the second London business day immediately preceding the first day of the relevant interest period (the “LIBOR determination date”). Promptly upon determination, the calculation agent will inform the trustee and us of the interest rate for the next interest period. Absent manifest error, the

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determination of the interest rate by the calculation agent shall be binding and conclusive on the holders of the floating rate notes, the trustee and us.

A “London business day” is a day on which dealings in deposits in U.S. dollars are transacted in the London interbank market.

The term “three-month LIBOR,” for any LIBOR determination date, means the London interbank offered rate for deposits in U.S. dollars having an index maturity of three months, in amounts of at least $1,000,000, as such rate appears on “Bloomberg Screen BBAM Page” at approximately 11:00 a.m., London time, on such LIBOR determination date, provided that if no offered rate appears on Bloomberg Screen BBAM Page on a LIBOR determination date at approximately 11:00 a.m., London time, then we will select four major banks in the London interbank market and the calculation agent shall request each of their principal London offices to provide a quotation of the rate at which three-month deposits in U.S. dollars in amounts of at least $1,000,000 are offered by it to prime banks in the London interbank market, on that date and at that time, that is representative of single transactions at that time. If at least two quotations are provided, LIBOR will be the arithmetic average of the quotations provided. Otherwise, we will select three major banks in New York City and the calculation agent shall request each of them to provide a quotation of the rate offered by them at approximately 11:00 a.m., New York City time, on the LIBOR determination date for loans in U.S. dollars to leading European banks having an index maturity of three months for the applicable interest period in an amount of at least $1,000,000 that is representative of single transactions at that time. If three quotations are provided, LIBOR will be the arithmetic average of the quotations provided. Otherwise, the rate of LIBOR for the next interest period will be equal to the rate of LIBOR for the then current interest period.

If LIBOR has been permanently discontinued, the calculation agent willuse, as directed by us, as a substitute for LIBOR and for each future LIBOR determination date, the alternative reference rate selected by the central bank, reserve bank, monetary authority or any similar institution (including any committee or working group thereof) that is consistent with accepted market practice (the “Alternative Rate”). As part of such substitution, the calculation agent will, as directed by us, make such adjustments to the Alternative Rate or the spread thereon, as well as the business day convention, determination dates and related provisions and definitions (“Adjustments”), in each case that are consistent with accepted market practice for the use of such Alternative Rate for debt obligations such as the notes. Provided however that if there is no clear market consensus as to whether any rate has replaced LIBOR in customary market usage, we may appoint in our sole discretion an independent financial advisor to determine an appropriate Alternative Rate, and any Adjustments, and the decision of the independent financial advisor will be binding on us, the calculation agent and the holders of the notes. If LIBOR has been permanently discontinued, but for any reason an Alternative Rate has not been determined or there is no such market practice for the use of such Alternative Rate (and an independent financial advisor has not determined an appropriate Alternative Rate and Adjustments), the rate of LIBOR for the next interest period will be set equal to the rate of LIBOR for the then current interest period.

“Bloomberg Screen BBAM Page” means the display designated as the Bloomberg screen “BBAM”, or such other page as may replace the Bloomberg screen “BBAM” on that service or such other service or services as may be nominated for the purpose of displaying London interbank offered rates for U.S. dollar deposits by ICE Benchmark Administration Limited (“IBA”) or its successor or such other entity assuming the responsibility of IBA or its successor in calculating the London interbank offered rate in the event IBA or its successor no longer does so.

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Upon written request from any holder of floating rate notes, the calculation agent will provide the interest rate in effect for the floating rate notes for the current interest period and, if it has been determined, the interest rate to be in effect for the next interest period.

All percentages resulting from any of the above calculations will be rounded, if necessary, to the nearest one hundred thousandth of a percentage point, with fiveone-millionths of a percentage point being rounded upwards (e.g., 8.986865% (or 0.08986865) being rounded to 8.98687% (or 0.0898687)) and all dollar amounts used in or resulting from such calculations will be rounded to the nearest cent (withone-half cent being rounded upwards).

The interest rate on the floating rate notes will in no event be higher than the maximum rate permitted by New York law as the same may be modified by United States laws of general application.

Dollar amounts resulting from such calculation will be rounded to the nearest cent, withone-half cent being rounded upward.

Fixed rate notes

The fixed rate notes will mature on                 ,                 . The fixed rate notes will bear interest at the rate of     % per annum. Interest on the fixed rate notes will accrue from and including                 , 2018 and will be payable in arrears semi-annually on                  and                  of each year, commencing on                 , 2019. The interest payable on the fixed rate notes on any interest payment date, subject to certain exceptions, will be paid to the person in whose name the fixed rate notes are registered at the close of business on the                  or                 , whether or not a business day, immediately preceding the next interest payment date. Interest will be computed on the basis of a360-day year consisting of twelve30-day months.

If an interest payment date or the maturity date for the fixed rate notes falls on a day that is not a business day, Comerica will postpone the interest payment or the payment of principal and interest at maturity to the next succeeding business day.

Optional redemption

At any time on and after                ,                  (30 days prior to the maturity date of the notes), we may redeem some or all of the notes of a series, at our option, at a redemption price equal to 100% of the principal amount of the notes being redeemed plus accrued and unpaid interest on the notes being redeemed to, but not including, the redemption date.

Notice of any redemption will be mailed (or with respect to global notes, to the extent permitted or required by applicable DTC procedures or regulations, sent electronically) at least 30 days but not more than 60 days before the redemption date to each holder of the notes to be redeemed by us or by the trustee on our behalf; provided that notice of redemption may be mailed or sent more than 60 days prior to a redemption date if the notice is issued in connection with a defeasance of the notes or a satisfaction and discharge of the notes. Unless we default in payment of the redemption price, on and after the redemption date, interest will cease to accrue on the notes or portions thereof called for redemption. If less than all of the notes are to be redeemed, the notes to be redeemed shall be selected by lot by DTC, in the case of notes represented by a global security, or by the trustee by a method the trustee deems to be fair and appropriate, in the case of notes that are not represented by a global security. Calculation of the redemption price will be made by us or on our behalf by such Person (as defined in the indenture) as Comerica shall designate; provided that such calculation or the correctness thereof shall not be a duty or obligation of the trustee.

Sinking fund

The notes will not be entitled to any sinking fund.

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Book-entry; delivery and form

The global notes

The notes of each series will be issued in the form of one or more registered notes in global form, without interest coupons. The global notes will be deposited on the issue date with DTC, as depository, and registered in the name of Cede & Co., as nominee of DTC, for credit to an account of a direct or indirect participant in DTC (including the Euroclear System (“Euroclear”) or Clearstream Banking, S.A. (“Clearstream”)) or will remain in the custody of the trustee pursuant to the FAST Balance Certificate Agreement between DTC and the trustee.

Except as described below, the global notes may be transferred in whole, and not in part, solely to another nominee of DTC or a successor to DTC or its nominee. All interests in the global notes may be subject to the procedures and requirements of DTC.

Certain book-entry procedures for the global notes

The descriptions of the operations and procedures of DTC described below are provided solely as a matter of convenience. These operations and procedures are solely within the control of DTC and are subject to change by them from time to time. We do not take any responsibility for these operations or procedures, and investors are urged to contact DTC or its participants directly to discuss these matters.

DTC has advised us that it is (1) a limited purpose trust company organized under the banking laws of the State of New York, (2) a “banking organization” within the meaning of the New York Banking Law, (3) a member of the Federal Reserve System, (4) a “clearing corporation” within the meaning of the New York Uniform Commercial Code, as amended and (5) a “clearing agency” registered pursuant to Section 17A of the Exchange Act. DTC was created to hold securities for its participants and facilitates the clearance and settlement of securities transactions between participants through electronic book-entry changes to the accounts of its direct participants, thereby eliminating the need for physical transfer and delivery of certificates. DTC’s participants include brokers and dealers, banks and trust companies, clearing corporations and certain other organizations. Indirect access to DTC’s system is also available to other entities such as banks, brokers, dealers and trust companies, referred to as “indirect participants,” that clear through or maintain a custodial relationship with a direct participant, either directly or indirectly. Investors who are not participants may beneficially own notes held by or on behalf of DTC only through direct participants or indirect participants.

Pursuant to procedures established by DTC, upon deposit of each of the global notes, DTC will credit the accounts of direct participants with an interest in the global notes. Ownership of the notes will be shown on, and the transfer of ownership of notes will be effected only through, records maintained by DTC, with respect to the interests of direct participants, and the records of direct participants and the indirect participants, with respect to the interests of persons other than direct participants.

Investors in the global notes may hold their interests therein directly through DTC, if they are participants in such system, or indirectly through organizations (including Euroclear and Clearstream) that are participants or indirect participants in such system. Euroclear and Clearstream will hold interests in the notes on behalf of their participants through customers’ securities accounts in their respective names on the books of their respective U.S. depositaries, which in turn, will hold such interests in the notes in customers’ securities accounts in the U.S. depositaries’ names on the books of DTC.

All interests in a global note, including those held through Euroclear or Clearstream, will be subject to the procedures and requirements of DTC. Those interests held through Euroclear or Clearstream will also be subject to the procedures and requirements of these systems.

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The laws of some jurisdictions may require that some types of purchasers of notes take physical delivery of the notes in certificated form. Accordingly, the ability to transfer interests in the notes represented by a global note to these persons may be limited. In addition, because DTC can act only on behalf of its direct participants, who in turn act on behalf of themselves or persons who hold interests through participants, the ability of a person having an interest in notes represented by a global note to pledge or transfer the interest to persons or entities that do not participate in DTC’s system, or to otherwise take actions in respect of the interest, may be affected by the lack of a physical certificated note in respect of the interest.

So long as DTC or its nominee is the registered owner of a global note, DTC or such nominee, as the case may be, will be considered the sole owner or holder of the interests represented by the global note for all purposes under the indenture. Except as provided below, owners of beneficial interests in a global note will not be entitled to have notes represented by the global note registered in their names, will not receive or be entitled to receive physical delivery of certificated notes, and will not be considered the owners or holders of those notes under the indenture for any purpose, including with respect to the giving of any direction, instruction or approval to the trustee under the indenture. Accordingly, each holder owning a beneficial interest in a global note must rely on the procedures of DTC and, if the holder is not a participant or an indirect participant, on the procedures of the participant and any other intermediaries through which the holder owns its interest, to exercise any rights of a holder of notes under the indenture or the global note.

We understand that under existing industry practice, in the event that we request any action of holders of notes, or an owner of a beneficial interest in a global note desires to take any action that DTC, as the holder of such global note, is entitled to take, DTC would authorize the participants to take the action and the participants would authorize beneficial owners owning through the participants to take the action or would otherwise act upon the instruction of the beneficial owners. Neither we nor the trustee will have any responsibility or liability for any aspect of the records relating to or payments made on account of notes by DTC, or for maintaining, supervising or reviewing any records of DTC relating to the notes. Payments with respect to the principal of, and premium, if any, liquidated damages, if any, and interest on, any notes represented by a global note registered in the name of DTC or its nominee on the applicable record date will be payable by the trustee to or at the direction of DTC or its nominee in its capacity as the registered holder of the global note representing the notes under the indenture. Under the terms of the indenture, we may treat, and the trustee may treat, the persons in whose names the notes, including the global notes, are registered as the owners of the notes for the purpose of receiving payment on the notes and for any and all other purposes whatsoever. Accordingly, neither we nor the trustee has or will have any responsibility or liability for the payment of these amounts to owners of beneficial interests in the global note, including principal, premium, if any, liquidated damages, if any, and interest.

Payments by the participants and the indirect participants to the owners of beneficial interests in the global notes will be governed by standing instructions and customary industry practice and will be the responsibility of the participants or the indirect participants.

Transfers between participants in DTC will be effected in accordance with DTC’s procedures, and will be settled insame-day funds. Transfers between participants in Euroclear and Clearstream will be effected in accordance with their respective rules and operating procedures.

Cross-market transfers between participants in DTC, on the one hand, and Euroclear or Clearstream participants, on the other hand, will be effected through DTC in accordance with DTC’s rules on behalf of Euroclear or Clearstream, as the case may be, by their depositaries. Crossmarket transactions will require delivery of instructions to Euroclear or Clearstream, as the case may be, by the counterparty in that system in accordance with the rules and procedures and within the established deadlines (Brussels time) of that system. Euroclear or Clearstream, as the case may be, will, if the transaction meets its settlement requirements, deliver

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instructions to its respective depositaries to take action to effect final settlement on its behalf by delivering or receiving interests in the relevant global note in DTC, and making or receiving payment in accordance with normal procedures forsame-day funds settlement applicable to DTC. Euroclear and Clearstream participants may not deliver instructions directly to the depositaries for Euroclear or Clearstream.

Because of time zone differences, the securities account of a Euroclear or Clearstream participant purchasing an interest in a global note from a participant in DTC will be credited and reported to the relevant Euroclear or Clearstream participant, during the securities settlement processing day (which must be a business day for Euroclear and Clearstream) immediately following the settlement date of DTC. DTC has advised us that cash received in Euroclear or Clearstream as a result of sales of interests in a global note by or through a Euroclear or Clearstream participant to a participant in DTC will be received with value on the settlement date of DTC but will be available in the relevant Euroclear or Clearstream cash account only as of the business day for Euroclear or Clearstream following DTC’s settlement date.

None of DTC, Euroclear or Clearstream is under any obligation to perform or to continue to perform such procedures, and such procedures may be discontinued at any time. Neither we nor the trustee will have any responsibility for the performance by DTC, Euroclear or Clearstream or their respective participants or indirect participants of their respective obligations under the rules and procedures governing their operations.

Certificated notes

If (1) DTC notifies us that it is no longer willing or able to act as a depository or clearing system for the notes or DTC ceases to be registered or in good standing under the Exchange Act, and a successor depository or clearing system is not appointed within 90 days after we have received notice or become aware of this condition, (2) we, at our option, notify the trustee in writing that we elect to cause the issuance of notes in certificated form under the indenture or (3) upon the occurrence and continuation of an event of default under the indenture, then, upon surrender by DTC of the global notes, certificated notes will be issued to each person that DTC identifies as the owner of the notes represented by the global notes. Upon any such issuance, the trustee is required to register the certificated notes in the name of the person or persons or the nominee of any of these persons and cause the same to be delivered to these persons.

Neither we nor the trustee will be liable for any delay by DTC or any participant or indirect participant in identifying the beneficial owners of the related notes and each such person may conclusively rely on, and will be protected in relying on, instructions from DTC for all purposes, including with respect to the registration and delivery, and the respective principal amounts, of the certificated notes to be issued.

Notices

Any notices required to be given to the holders of the notes will be given to DTC.

Trustee and calculation agent

The Bank of New York Mellon Trust Company, N.A. will act as trustee for the notes. The Bank of New York Mellon Trust Company, N.A. will also act as calculation agent for the floating rate notes, until such time as we appoint a successor calculation agent. From time to time, we and some of our subsidiaries may maintain deposit accounts and conduct other banking transactions, including lending transactions, with the trustee in the ordinary course of business. Additionally, we maintain banking relationships with The Bank of New York Mellon Trust Company, N.A. and its affiliates in the ordinary course of business. These banking relationships include The Bank of New York Mellon Trust Company, N.A. and its affiliates serving as trustee under indentures involving our existing debt securities and general banking services. Upon the occurrence of an event of default or an event which,

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after notice or lapse of time or both, would become an event of default under the notes, or upon the occurrence of a default under another indenture under which The Bank of New York Mellon Trust Company, N.A. serves as trustee, the trustee may be deemed to have a conflicting interest with respect to the other debt securities as to which we are not in default for purposes of the Trust Indenture Act and, accordingly, may be required to resign as trustee under the indenture. In that event, we would be required to appoint a successor trustee. The trustee is under no obligation to exercise any of the rights or powers vested in it by the indenture at the request or direction of any of the holders pursuant to the Indenture, unless such holders have offered to the trustee security or indemnity satisfactory to the trustee against the costs, expenses and liabilities which might be incurred by it in compliance with such request or direction.

Governing law

The indenture and the notes are governed by and will be construed in accordance with the laws of the State of New York.

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Certain United States federal income tax consequences

The following is a summary of certain United States federal income tax consequences of the acquisition, ownership and disposition of the notes by U.S. Holders (as defined below) andNon-U.S. Holders (as defined below), in each case, who acquire the notes pursuant to the offering. This summary is based upon the United States Internal Revenue Code of 1986, as amended (the “Code”), the Treasury Regulations (the “Regulations”) promulgated thereunder, and administrative and judicial interpretations thereof, all as of the date hereof and all of which are subject to change, possibly on a retroactive basis, and any such change or interpretation could affect the accuracy of the statements in this summary. This summary is limited to the tax consequences with respect to notes that are purchased by an initial holder at their original issue price for cash and that are held as capital assets within the meaning of Section 1221 of the Code (generally, property held for investment). This summary does not address the tax consequences to subsequent purchasers of the notes. This summary assumes that the notes will be treated as debt instruments for United States federal income tax purposes. This summary does not purport to deal with all aspects of United States federal income taxation that might be relevant to particular holders in light of their circumstances or status, nor does it address specific tax consequences that may be relevant to particular holders (including, for example, financial institutions, broker-dealers, traders in securities that electmark-to-market treatment, insurance companies, partnerships or other pass-through entities and investors therein, United States expatriates,tax-exempt persons, controlled foreign corporations or passive foreign investment companies, U.S. Holders that have a functional currency other than the United States dollar, persons who hold notes as part of a straddle, hedge, conversion or other integrated or risk-reduction transaction, retirement plans, regulated investment companies or holders required to accelerate the recognition of any item of gross income with respect to the notes as a result of such income being recognized on an applicable financial statement“. In addition, this summary does not address tax consequences arising under the unearned income Medicare contribution tax pursuant to the Health Care and Education Reconciliation Act of 2010, nor does it address United States federal alternative minimum, estate and gift tax consequences or consequences under the tax laws of any state, local or foreign jurisdiction. We have not sought, and will not seek, any ruling from the Internal Revenue Service (the “IRS”) with respect to the statements made and the conclusions reached in this summary, and we cannot assure you that the IRS will agree with such statements and conclusions.

If a partnership holds notes, the tax treatment of a partner in the partnership generally will depend upon the status of the partner and the activities of the partnership. If you are a partner in a partnership holding notes, you should consult your tax advisor.

THIS SUMMARY IS FOR GENERAL INFORMATION ONLY. PROSPECTIVE PURCHASERS OF THE NOTES ARE URGED TO CONSULT THEIR OWN TAX ADVISORS CONCERNING THE UNITED STATES FEDERAL INCOME TAXATION AND OTHER TAX CONSEQUENCES TO THEM OF ACQUIRING, OWNING AND DISPOSING OF THE NOTES, AS WELL AS THE APPLICATION OF STATE, LOCAL AND FOREIGN INCOME AND OTHER TAX LAWS.

For purposes of the following summary, a “U.S. Holder” is a beneficial owner of notes that is, for United States federal income tax purposes, (i) a citizen or individual resident of the United States; (ii) a corporation or other entity or arrangement taxable as a corporation created or organized under the laws of the United States, any state thereof, or the District of Columbia; (iii) an estate, the income of which is subject to United States federal income tax regardless of its source; or (iv) a trust, if a court within the United States is able to exercise primary supervision over the trust’s administration and one or more United States persons have the authority to control all of its substantial decisions or if a valid election to be treated as a United States person is in effect with respect to such trust. A“Non-U.S. Holder” is a beneficial owner of notes that is neither a U.S. Holder nor a partnership for United States federal income tax purposes.

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United States federal income taxation of U.S. Holders

Payments of stated interest

It is expected and this discussion assumes that either the issue price of the notes will equal the stated redemption price of the notes or the notes will be issued with no more than ade minimis amount of original issue discount. Accordingly, stated interest on a note will generally be taxable to a U.S. Holder as ordinary income at the time such interest is received or accrued, depending on the holder’s regular method of accounting for United States federal income tax purposes.

Disposition of the notes

Upon the sale, exchange or other taxable disposition of a note, a U.S. Holder will generally recognize taxable gain or loss equal to the difference between (i) the sum of all cash plus the fair market value of all other property received on such disposition (except to the extent such cash or other property is attributable to accrued but unpaid interest, which is treated as interest as described above) and (ii) such holder’s adjusted tax basis in the note. A U.S. Holder’s adjusted tax basis in a note generally will equal the cost of the note to such holder less any principal payments received by that U.S. Holder. Any gain or loss recognized on the disposition of a note generally will be capital gain or loss, and will be long-term capital gain or loss if, at the time of such disposition, the U.S. Holder’s holding period for the note is more than one year. Long-term capital gain ofnon-corporate U.S. Holders is generally taxed at preferential rates. The deductibility of capital losses is subject to limitations.

Backup withholding and information reporting

For each calendar year in which the notes are outstanding, we generally are required to provide the IRS with certain information, including the beneficial owner’s name, address and taxpayer identification number, the aggregate amount of interest paid to that beneficial owner during the calendar year and the amount of tax withheld, if any, unless the U.S. Holder is an exempt recipient.

We, our agent or paying agents, or a broker will be required to “backup” withhold at the applicable rate (currently 24% for payments made before January 1, 2026) on each payment on the notes and on the proceeds from a sale of the notes unless a U.S. Holder subject to the reporting requirements described above provides to us its correct taxpayer identification number in the manner required by applicable law or otherwise establishes an exemption.

Backup withholding is not an additional tax and may generally be refunded or credited against the U.S. Holder’s United States federal income tax liability, provided that the required information is timely furnished to the IRS.

U.S. Holders should consult their own tax advisors regarding their qualifications for an exemption from backup withholding, and the procedure for establishing such exemption, if applicable.

United States federal income taxation ofNon-U.S. Holders

Payments of interest

Subject to the discussion of backup withholding below, payments of interest on the notes to aNon-U.S. Holder will generally not be subject to United States federal withholding tax under the “portfolio interest exemption,” provided that:

1. such payments are not effectively connected with the conduct of a United States trade or business, or in the case of an income tax treaty resident, a United States permanent establishment maintained by theNon-U.S. Holder in the United States;

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2. theNon-U.S. Holder does not actually or constructively own 10% or more of the total combined voting power of all classes of our stock entitled to vote within the meaning of the Code and applicable Regulations;

3. theNon-U.S. Holder is not a controlled foreign corporation that, for United States federal income tax purposes, is related (within the meaning of Section 864(d)(4) of the Code) to us; and

4. either (a) the beneficial owner of the notes certifies on a properly completed and executed IRS FormW-8BEN or IRS FormW8-BEN-E (or a suitable substitute form or successor form), under penalties of perjury, that it is not a “U.S. person” (as defined in the Code) and provides its name and address, or (b) a securities clearing organization, bank or other financial institution that holds customers’ securities in the ordinary course of its trade or business (a “financial institution”) and holds the notes on behalf of the beneficial owner certifies to us or our agent, under penalties of perjury, that a properly completed and executed IRS FormW-8BEN or IRS FormW-8BEN-E, as applicable (or a suitable substitute or successor form) has been received from the beneficial owner by it or by a financial institution between it and the beneficial owner and furnishes us with a copy thereof.

If aNon-U.S. Holder cannot satisfy the requirements of the “portfolio interest exemption,” payments of interest made to suchNon-U.S. Holder will be subject to a 30% United States federal withholding tax unless the beneficial owner of the note provides a properly completed and executed:

1. IRS FormW-8BEN or IRS FormW-8BEN-E, as applicable (or a suitable substitute or successor form) claiming, under penalties of perjury, an exemption from, or reduction in, withholding tax under an applicable income tax treaty, or

2. IRS FormW-8ECI (or successor form) stating that interest paid on the note is not subject to withholding tax because it is effectively connected with a United States trade or business or, if certain treaties apply, it is attributable to a permanent establishment maintained in the United States of the beneficial owner (in which case such interest will be subject to regular graduated United States tax rates as described below).

Non-U.S. Holders should consult their own tax advisors about the specific methods for satisfying these requirements. A claim for exemption will not be valid if the person receiving the applicable form has actual knowledge or reason to know that the statements on the form are false.

If interest on the note is effectively connected with a United States trade or business of the beneficial owner (and if required by an applicable income tax treaty, attributable to a United States permanent establishment), theNon-U.S. Holder, although exempt from the withholding tax described above, will be subject to United States federal income tax on such interest on a net income basis in the same manner as if it were a U.S. Holder. In addition, if suchNon-U.S. Holder is a foreign corporation, it may be subject to a branch profits tax equal to 30% (unless reduced by an applicable income tax treaty) in respect of such interest.

Disposition of the notes

No withholding of United States federal income tax will generally be required with respect to any gain or income realized by aNon-U.S. Holder upon the sale, exchange or other disposition of a note (except to the extent such income is attributable to accrued but unpaid interest, which will be treated as interest as described above under “—United States federal income taxation ofNon-U.S. Holders—Payments of interest”).

Except with respect to accrued and unpaid interest, aNon-U.S. Holder will not be subject to United States federal income tax on gain realized on the sale, exchange or other disposition of a note unless:

• theNon-U.S. Holder is an individual who is present in the United States for a period or periods aggregating 183 or more days in the taxable year of the disposition and certain other conditions are met, or

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• such gain or income is effectively connected with a United States trade or business (and, if required by an applicable treaty, is attributable to a United States permanent establishment).

Gain described in the first bullet point above generally will be subject to U.S. federal income tax on a net income basis at the regular graduated U.S. federal income tax rates in the same manner as if suchNon-U.S. Holder were a U.S. person. ANon-U.S. Holder that is a corporation also may be subject to an additional “branch profits tax” at a rate of 30% (or such lower rate as may be specified by an applicable income tax treaty) of its “effectively connected earnings and profits” for the taxable year, subject to certain adjustments.

Gain described in the second bullet point above generally will be subject to U.S. federal income tax at a 30% rate (or such lower rate as may be specified by an applicable income tax treaty), but may be offset by U.S. source capital losses, if any, of theNon-U.S. Holder.

Backup withholding and information reporting

United States backup withholding will not apply to payments of interest on a note or proceeds from the sale or other disposition of a note payable to aNon-U.S. Holder if the certification described in “—United States federal income taxation ofNon-U.S. Holders—Payments of interest” is duly provided by suchNon-U.S. Holder or theNon-U.S. Holder otherwise establishes an exemption, provided that the payor does not have actual knowledge that the holder is a U.S. person or that the conditions of any claimed exemption are not satisfied. Certain information reporting still may apply to interest payments even if an exemption from backup withholding is established. Copies of any information returns reporting interest payments and any withholding also may be made available to the tax authorities in the country in which aNon-U.S. Holder resides under the provisions of an applicable income tax treaty.

Backup withholding is not an additional tax. Any amounts withheld under the backup withholding tax rules from a payment to aNon-U.S. Holder will be allowed as a refund or a credit against suchNon-U.S. Holder’s United States federal income tax liability, provided that the requisite procedures are followed.

Non-U.S. Holders should consult their own tax advisors regarding their particular circumstances and the availability of and procedure for establishing an exemption from backup withholding.

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Certain ERISA considerations

The following is a summary of certain considerations associated with the purchase of the notes, holding and, to the extent relevant, disposition of notes by an employee benefit plan subject to Title I of the Employee Retirement Income Security Act of 1974, as amended (“ERISA”), a plan described in Section 4975 of the Code, including an individual retirement account (“IRA”) or a Keogh plan, a plan subject to provisions under applicable federal, state, local,non-U.S. or other laws or regulations that are similar to the provisions of Title I of ERISA or Section 4975 of the Code (“Similar Laws”) and any entity whose underlying assets include “plan assets” by reason of any such employee benefit or retirement plan’s investment in such entity (each of which we refer to as a “Plan”).

General fiduciary matters.    ERISA and the Code impose certain duties on persons who are fiduciaries of a Plan subject to Title I of ERISA and prohibit certain transactions involving the assets of a Plan subject to Title I of ERISA or Section 4975 of the Code (an “ERISA Plan”) with its fiduciaries or other interested parties. In general, under ERISA and the Code, any person who exercises any discretionary authority or control over the administration of such an ERISA Plan or the management or disposition of the assets of such an ERISA Plan, or who renders investment advice for a fee or other compensation to such an ERISA Plan, is generally considered to be a fiduciary of the ERISA Plan. Plans that are governmental plans (as defined in Section 3(32) of ERISA) and certain church plans (as defined in Section 3(33) of ERISA or Section 4975(g)(3) of the Code) are not subject to the requirements of ERISA or Section 4975 of the Code (but may be subject to similar prohibitions under Similar Laws).

In considering the acquisition, holding and, to the extent relevant, disposition of notes with a portion of the assets of a Plan, a fiduciary should determine whether the investment is in accordance with the documents and instruments governing the Plan and the applicable provisions of ERISA, the Code or any Similar Law relating to a fiduciary’s duties to the Plan including, without limitation, the prudence, diversification, delegation of control and prohibited transaction provisions of ERISA, the Code and any other applicable Similar Laws.

Prohibited transaction issues.    Section 406 of ERISA prohibits ERISA Plans from engaging in specified transactions involving plan assets with persons or entities who are “parties in interest,” within the meaning of Section 3(14) of ERISA, and Section 4975 of the Code imposes an excise tax on certain “disqualified persons,” within the meaning of Section 4975 of the Code, who engage in similar transactions, in each case unless an exemption is available. A party in interest or disqualified person who engages in anon-exempt prohibited transaction may be subject to excise taxes and other penalties and liabilities under ERISA and the Code. In addition, the fiduciary of an ERISA Plan that engages in such anon-exempt prohibited transaction may be subject to penalties and liabilities under ERISA and the Code. In the case of an IRA, the occurrence of a prohibited transaction could cause the IRA to lose itstax-exempt status.

The underwriters, the Company or their respective affiliates may be parties in interest or disqualified persons with respect to ERISA Plans and the acquisition and/or holding of notes by an ERISA Plan with respect to which the issuer, the underwriters or a guarantor (or certain of our or their affiliates) is considered a party in interest or a disqualified person may constitute or result in a direct or indirect prohibited transaction under Section 406 of ERISA and/or Section 4975 of the Code, unless the investment is acquired and is held in accordance with an applicable statutory, class or individual prohibited transaction exemption. In this regard, the U.S. Department of Labor has issued prohibited transaction class exemptions, or “PTCEs,” that may apply to the acquisition and holding of the notes. These class exemptions include, without limitation, PTCE84-14 respecting transactions determined by independent qualified professional asset managers, PTCE90-1 respecting insurance company pooled separate accounts, PTCE91-38 respecting bank collective investment funds, PTCE95-60 respecting life insurance company general accounts and PTCE96-23 respecting transactions determined byin-house asset managers. In addition, Section 408(b)(17) of ERISA and Section 4975(d)(20) of the Code each provide a limited exemption, commonly referred to as the “service provider exemption,” from the prohibited transaction

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provisions of ERISA and Section 4975 of the Code for certain transactions between an ERISA Plan and a person that is a party in interest and/or a disqualified person (other than a fiduciary or an affiliate that, directly or indirectly, has or exercises any discretionary authority or control or renders any investment advice with respect to the assets of any ERISA Plan involved in the transaction) solely by reason of providing services to the Plan or by relationship to a service provider, provided that the ERISA Plan pays no more than adequate consideration in connection with the transaction. There can be no assurance that all of the conditions of any such exemptions will be satisfied at the time that the notes are acquired by a purchaser or transferee, or thereafter, if the facts relied upon for utilizing a prohibited transaction exemption change.

Because of the foregoing, the notes should not be acquired or held by any person investing “plan assets” of any Plan, unless such acquisition and holding will not constitute anon-exempt prohibited transaction under ERISA or Section 4975 of the Code or similar violation of any applicable Similar Laws.

Representation.    Each purchaser, transferee and holder of notes will be deemed to have represented and warranted that either (i) it is not a Plan and no portion of the assets used to acquire or hold the notes constitutes assets of any Plan or (ii) (A) the purchase and holding of a note will not constitute anon-exempt prohibited transaction under Section 406 of ERISA or Section 4975 of the Code or a violation of any applicable Similar Laws and (B) neither the Company nor any of our affiliates is acting as a fiduciary (within the meaning of Section 3(21) of ERISA) in connection with the purchase or holding of the notes and has not provided any advice concerning the purchase or holding of the notes..

The foregoing discussion is general in nature and is not intended to beall-inclusive. Due to the complexity of these rules and the penalties that may be imposed upon persons involved innon-exempt prohibited transactions, it is particularly important that fiduciaries or other persons considering acquiring notes on behalf of, or with the assets of, any Plan, consult with their counsel regarding the potential applicability of ERISA, Section 4975 of the Code and any Similar Laws to such investment and whether an exemption would be applicable to the acquisition and holding of the notes. The acquisition and holding of notes by any Plan is in no respect a representation by us, the underwriters or any of their respective affiliates or representatives that such an investment meets all relevant legal requirements with respect to investments by such Plans generally or any particular Plan, or that such an investment is appropriate for Plans generally or any particular Plan.

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Underwriting (Conflicts of interest)

Under the terms and subject to the conditions contained in an underwriting agreement, dated                 , 2018 (the “underwriting agreement”), the underwriters named below (the “underwriters”), for whom J.P. Morgan Securities LLC, Morgan Stanley & Co. LLC and RBC Capital Markets, LLC are acting as representatives (the “representatives”), have severally agreed to purchase, and we have agreed to sell to them, severally, the respective principal amount of notes of each series set forth opposite their names below:

Underwriter	Principal amount of floating rate notes	Principal amount of fixed rate notes
J.P. Morgan Securities LLC	$	$
Morgan Stanley & Co. LLC
RBC Capital Markets, LLC
Comerica Securities, Inc.
Total:	$	$

The underwriting agreement provides that the underwriters are obligated to purchase all of the notes of a series if any are purchased.

The underwriters propose to offer the notes of each series directly to the public at the public offering prices on the cover page of this prospectus supplement and may offer the notes to certain dealers at the public offering prices less concessions not to exceed     % of the principal amount of the floating rate notes and less concessions not to exceed     % of the principal amount of the fixed rate notes. The underwriters may allow, and dealers may reallow, a concession not to exceed     % of the principal amount of the floating rate notes and a concession not to exceed     % of the principal amount of the fixed rate notes on sales to other dealers. After the initial offering of the notes, the price to public and other selling terms of a series of notes may from time to time be varied by the underwriters. The offering of the notes by the underwriters is subject to receipt and acceptance and subject to the underwriters’ right to reject any order in whole or in part.

The aggregate proceeds to us for each series of notes are set forth on the cover page of this prospectus supplement before deducting our expenses in offering the notes. We estimate that we will pay approximately $                million for expenses, excluding underwriting discounts, allocable to the offering.

We have agreed to indemnify the several underwriters against certain liabilities, including liabilities under the Securities Act of 1933, as amended, or to contribute to payments that the underwriters may be required to make in respect thereof.

Each series of notes are new issues of securities with no established trading market. One or more underwriters intend to make a secondary market for each series of the notes. However, they are not obligated to do so and may discontinue making a secondary market for each series of the notes at any time without notice. No assurance can be given as to how liquid the trading market for each series of the notes will be.

In connection with the offering, the underwriters may engage in transactions that stabilize the market prices of the notes. Such transactions consist of bids or purchases to peg, fix or maintain the prices of the notes. If the underwriters create a short position in the notes in connection with the offering, i.e., if they sell more notes than are listed on the cover page of this prospectus supplement, the underwriters may reduce that short position by purchasing notes in the open market. Purchases of a security to stabilize the prices or to reduce a short position may cause the prices of the notes to be higher than they might be in the absence of these purchases.

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The underwriters also may impose a penalty bid. This occurs when a particular underwriter repays to the underwriters a portion of the underwriting discount received by it because the representatives have repurchased notes sold by or for the account of such underwriter in stabilizing or short covering transactions.

Neither we nor the underwriters make any representation or prediction as to the direction or magnitude of any effect that the transactions described above may have on the prices of the notes. In addition, neither we nor the underwriters make any representation that the underwriters will engage in these transactions or that these transactions, once commenced, will not be discontinued without notice.

The underwriters and their respective affiliates are full service financial institutions engaged in various activities, which may include securities trading, commercial and investment banking, financial advisory, investment management, investment research, principal investment, hedging, market making, brokerage and other financing andnon-financial activities and services. Some of the underwriters and their affiliates have engaged in, and may in the future engage in, investment banking and other commercial dealings in the ordinary course of business with us or our affiliates. They have received, or may in the future receive customary fees and commissions for these transactions.

In addition, in the ordinary course of their business activities, the underwriters and their affiliates may make or hold a broad array of investments, including serving as counterparties to certain derivative and hedging arrangements, and may actively trade debt and equity securities (or related derivative securities) and financial instruments (including bank loans) for their own account and for the accounts of their customers. Such investments and securities activities may involve securities and/or instruments of ours or our affiliates. Certain of the underwriters or their affiliates that have a lending relationship with us routinely hedge their credit exposure to us consistent with their customary risk management policies. Typically, such underwriters and their affiliates would hedge such exposure by entering into transactions which consist of either the purchase of credit default swaps or the creation of short positions in our securities, including potentially the notes offered hereby. Any such credit default swaps or short positions could adversely affect future trading prices of the notes offered hereby. The underwriters and their affiliates may also make investment recommendations and/or publish or express independent research views in respect of such securities or financial instruments and may hold, or recommend to clients that they acquire, long and/or short positions in such securities and instruments.

Conflicts of interest

Our affiliate and one of the underwriters in this offering, Comerica Securities, Inc., is a member of FINRA and is participating in the distribution of the offered securities. The distribution arrangements for this offering comply with the requirements of FINRA Rule 5121 regarding a FINRA member’s firm participation in the distribution of securities of an affiliate. In accordance with Rule 5121, no FINRA member firm that has a conflict of interest under Rule 5121 may make sales in this offering to any discretionary account without the prior approval of the customer. Our affiliates, including Comerica Securities, Inc., may use this prospectus supplement and the attached prospectus in connection with offers and sales of the notes in the secondary market. These affiliates may act as principal or agent in those transactions, but are not primarily responsible for managing this offering. Secondary market sales will be made at prices related to market prices at the time of sale.

Alternative Settlement Cycle

It is expected that delivery of the notes will be made against payment therefor on or about                , 2018, which is the third business day following the date hereof (such settlement cycle being referred to as “T+3”). Pursuant toRule 15c6-1 under the Exchange Act, trades in the secondary market generally are required to settle in two business days unless the parties to any such trade expressly agree otherwise. Accordingly, purchasers

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who wish to trade the notes on the date of pricing will be required, by virtue of the fact that the notes initially will settle in T+3, to specify an alternative settlement cycle at the time of any such trade to prevent failed settlement. Purchasers of the notes who wish to trade such notes on the date of pricing should consult their own advisors.

Selling restrictions

European Economic Area

The notes are not intended to be offered, sold or otherwise made available to and should not be offered, sold or otherwise made available to any retail investor in the European Economic Area (“EEA”). For these purposes, a retail investor means a person who is one (or more) of: (i) a retail client as defined in point (11) of Article 4(1) of Directive 2014/65/EU (as amended, “MiFID II”); or (ii) a customer within the meaning of Directive 2002/92/EC (as amended, the “Insurance Mediation Directive”), where that customer would not qualify as a professional client as defined in point (10) of Article 4(1) of MiFID II; or (iii) not a qualified investor as defined in Directive 2003/71/EC (as amended, the “Prospectus Directive”). Consequently no key information document required by Regulation (EU) No 1286/2014 (as amended, the “PRIIPs Regulation”) for offering or selling the notes or otherwise making them available to retail investors in the EEA has been prepared and therefore offering or selling the notes or otherwise making them available to any retail investor in the EEA may be unlawful under the PRIIPS Regulation. This prospectus supplement and the accompanying prospectus have been prepared on the basis that any offer of notes in any Member State of the EEA will be made pursuant to an exemption under the Prospectus Directive from the requirement to publish a prospectus for offers of notes. This prospectus supplement and the accompanying prospectus is not a prospectus for the purposes of the Prospectus Directive.

United Kingdom

In addition, in the United Kingdom, this document is being distributed only to, and is directed only at, and any offer subsequently made may only be directed at persons who are “qualified investors” (as defined in the Prospectus Directive) (i) who have professional experience in matters relating to investments falling within Article 19 (5) of the Financial Services and Markets Act 2000 (Financial Promotion) Order 2005, as amended (the “Order”) and/or (ii) who are high net worth companies (or persons to whom it may otherwise be lawfully communicated) falling within Article 49(2)(a) to (d) of the Order (all such persons together being referred to as “relevant persons”). This document must not be acted on or relied on in the United Kingdom by persons who are not relevant persons. In the United Kingdom, any investment or investment activity to which this document relates is only available to, and will be engaged in with, relevant persons.

Hong Kong

The notes may not be offered or sold by means of any document other than (i) in circumstances which do not constitute an offer to the public within the meaning of the Companies Ordinance (Cap.32, Laws of Hong Kong), or (ii) to “professional investors” within the meaning of the Securities and Futures Ordinance (Cap.571, Laws of Hong Kong) and any rules made thereunder, or (iii) in other circumstances which do not result in the document being a “prospectus” within the meaning of the Companies Ordinance (Cap.32, Laws of Hong Kong), and no advertisement, invitation or document relating to the notes may be issued or may be in the possession of any person for the purpose of issue (in each case whether in Hong Kong or elsewhere), which is directed at, or the contents of which are likely to be accessed or read by, the public in Hong Kong (except if permitted to do so under the laws of Hong Kong) other than with respect to notes which are or are intended to be disposed of only to persons outside Hong Kong or only to “professional investors” within the meaning of the Securities and Futures Ordinance (Cap. 571, Laws of Hong Kong) and any rules made thereunder.

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The contents of this prospectus supplement and the accompanying prospectus have not been reviewed by any regulatory authority in Hong Kong. You are advised to exercise caution in relation to the offering of the notes. If you are in any doubt about any of the contents of this document, you should obtain independent professional advice.

Japan

The notes have not been and will not be registered under the Financial Instruments and Exchange Law of Japan (the “Financial Instruments and Exchange Law”) and each underwriter has agreed that it will not offer or sell any notes, directly or indirectly, in Japan or to, or for the benefit of, any resident of Japan (which term as used herein means any person resident in Japan, including any corporation or other entity organized under the laws of Japan), or to others forre-offering or resale, directly or indirectly, in Japan or to a resident of Japan, except pursuant to an exemption from the registration requirements of, and otherwise in compliance with, the Financial Instruments and Exchange Law and any other applicable laws, regulations and ministerial guidelines of Japan.

Singapore

This prospectus supplement and the accompanying prospectus have not been registered as a prospectus with the Monetary Authority of Singapore. Accordingly, this prospectus supplement, the accompanying prospectus and any other document or material in connection with the offer or sale, or invitation for subscription or purchase, of the notes may not be circulated or distributed, nor may the notes be offered or sold, or be made the subject of an invitation for subscription or purchase, whether directly or indirectly, to persons in Singapore other than (i) to an institutional investor under Section 274 of the Securities and Futures Act, Chapter 289 of Singapore (the “SFA”), (ii) to a relevant person pursuant to Section 275(2) of the SFA, or any person pursuant to Section 275(1A) of the SFA, and in accordance with the conditions specified in Section 275 of the SFA or (iii) otherwise pursuant to, and in accordance with the conditions of, any other applicable provision of the SFA, in each case subject to compliance with conditions set forth in the SFA.

Where the notes are subscribed or purchased under Section 275 of the SFA by a relevant person which is a corporation (which is not an accredited investor (as defined in Section 4A of the SFA)) the sole business of which is to hold investments and the entire share capital of which is owned by one or more individuals, each of whom is an accredited investor, the securities (as defined in Section 239(1) of the SFA) of that corporation shall not be transferable for six months after that corporation has acquired the notes under Section 275 of the SFA except: (1) to an institutional investor under Section 274 of the SFA or to a relevant person (as defined in Section 275(2) of the SFA), (2) where such transfer arises from an offer in that corporation’s securities pursuant to Section 275(1A) of the SFA, (3) where no consideration is or will be given for the transfer, (4) where the transfer is by operation of law, (5) as specified in Section 276(7) of the SFA, or (6) as specified in Regulation 32 of the Securities and Futures (Offers of Investments) (Shares and Debentures) Regulations 2005 of Singapore (“Regulation 32”).

Where the notes are subscribed or purchased under Section 275 of the SFA by a relevant person which is a trust (where the trustee is not an accredited investor (as defined in Section 4A of the SFA)) whose sole purpose is to hold investments and each beneficiary of the trust is an accredited investor, the beneficiaries’ rights and interest (howsoever described) in that trust shall not be transferable for six months after that trust has acquired the notes under Section 275 of the SFA except: (1) to an institutional investor under Section 274 of the SFA or to a relevant person (as defined in Section 275(2) of the SFA), (2) where such transfer arises from an offer that is made on terms that such rights or interest are acquired at consideration of not less than $200,000 (or its equivalent in a foreign currency) for each transaction (whether such amount is to be paid for in cash or by exchange of securities or other assets), (3) where no consideration is or will be given for the transfer,

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(4) where the transfer is by operation of law, (5) as specified in Section 276(7) of the SFA, or (6) as specified in Regulation 32.

Canada

The notes may be sold only to purchasers purchasing, or deemed to be purchasing, as principal that are accredited investors, as defined in NationalInstrument 45-106 Prospectus Exemptions or subsection 73.3(1) of the Securities Act (Ontario), and are permitted clients, as defined in NationalInstrument 31-103 Registration Requirements, Exemptions and Ongoing Registrant Obligations. Any resale of the notes must be made in accordance with an exemption from, or in a transaction not subject to, the prospectus requirements of applicable securities laws.

Securities legislation in certain provinces or territories of Canada may provide a purchaser with remedies for rescission or damages if this prospectus supplement (including any amendment thereto) contains a misrepresentation, provided that the remedies for rescission or damages are exercised by the purchaser within the time limit prescribed by the securities legislation of the purchaser’s province or territory. The purchaser should refer to any applicable provisions of the securities legislation of the purchaser’s province or territory for particulars of these rights or consult with a legal advisor.

Pursuant to section 3A.3 of NationalInstrument 33-105 Underwriting Conflicts(“NI 33-105”), the underwriters are not required to comply with the disclosure requirements ofNI 33-105 regarding underwriter conflicts of interest in connection with this offering.

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Legal matters

The validity of the notes offered hereby and certain other legal matters relating to the offering will be passed upon for us by Wachtell, Lipton, Rosen & Katz, special counsel to Comerica, and by Ms. Jennifer S. Perry, Senior Vice President and Assistant General Counsel, Corporate Finance and Securities. Ms. Perry beneficially owns or has rights to acquire an aggregate of less than 1% of Comerica’s common stock. Certain legal matters will be passed upon for the underwriters by Mayer Brown LLP. From time to time, Mayer Brown LLP has represented Comerica and its subsidiaries on various matters and may do so in the future.

Experts

The consolidated financial statements of Comerica appearing in our Annual Report on Form10-K for the year ended December 31, 2017, and the effectiveness of Comerica’s internal control over financial reporting as of December 31, 2017, have been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their reports thereon, included therein, and incorporated herein by reference. Such consolidated financial statements are incorporated herein by reference in reliance upon such reports given on the authority of such firm as experts in accounting and auditing.

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PROSPECTUS

Comerica Incorporated

Common Stock

Preferred Stock

Depositary Shares

Debt Securities

Warrants to Purchase Common Stock, Preferred Stock and Debt Securities

Stock Purchase Contracts

Stock Purchase Units

The securities listed above may be offered and sold from time to time by Comerica, and also may be offered and sold, from time to time, by one or more selling securityholders to be identified in the future. Comerica will provide the specific terms of these securities in supplements to this prospectus. You should read this prospectus and the applicable prospectus supplement carefully before you invest in any of these securities.

Comerica’s common stock is traded on the New York Stock Exchange under the symbol “CMA.”

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

Investing in these securities involves risks. See “Risk Factors” on page 4 of this prospectus and on page 11 of our Annual Report on Form10-K for the year ended December 31, 2017, and in other documents that Comerica subsequently files with the Securities and Exchange Commission which are incorporated by reference into this prospectus. Additional risk factors may also be set forth in any applicable prospectus supplement.

These securities are not deposits or savings accounts but are unsecured obligations of Comerica. These securities are not insured by the Federal Deposit Insurance Corporation or any other governmental agency or instrumentality.

February 16, 2018

TABLE OF CONTENTS

ABOUT THIS PROSPECTUS	3
FORWARD-LOOKING STATEMENTS	3
COMERICA INCORPORATED	4
RISK FACTORS	4
USE OF PROCEEDS	5
CONSOLIDATED RATIO OF EARNINGS TO FIXED CHARGES	5
DESCRIPTION OF CAPITAL STOCK	5
DESCRIPTION OF DEPOSITARY SHARES	9
DESCRIPTION OF DEBT SECURITIES	12
DESCRIPTION OF THE WARRANTS TO PURCHASE COMMON STOCK OR PREFERRED STOCK	19
DESCRIPTION OF THE WARRANTS TO PURCHASE DEBT SECURITIES	21
DESCRIPTION OF STOCK PURCHASE CONTRACTS AND STOCK PURCHASE UNITS	22
PLAN OF DISTRIBUTION	22
ERISA CONSIDERATIONS	24
LEGAL MATTERS	26
EXPERTS	26
WHERE YOU CAN FIND MORE INFORMATION	26

You should rely only on the information contained or incorporated by reference in this prospectus or any supplement. Comerica has not authorized anyone else to provide you with different information. Comerica is offering these securities only in states where the offer is permitted. You should not assume that the information in this prospectus or any supplement is accurate as of any date other than the date on the front of those documents. Comerica’s business, financial condition, results of operations and prospects may have changed since that date.

In this prospectus, unless the context requires otherwise, references to “Comerica,”, “we,” “us” or “our” are to Comerica Incorporated and its consolidated subsidiaries.

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ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement (the “Registration Statement”) that Comerica filed with the Securities and Exchange Commission (the “SEC”) under the Securities Act of 1933, as amended (the “Securities Act”) using a “shelf” registration process. Under this shelf process, we are registering an unspecified amount of each class of the securities described in this prospectus, and may sell any combination of these securities in one or more offerings. This prospectus provides you with a general description of the securities Comerica may offer. Each time Comerica sells securities, it will provide a prospectus supplement that will contain specific information about the terms of that offering. The prospectus supplement may also add, update or change information contained in this prospectus. You should read both this prospectus and any prospectus supplement together with the additional information described under the heading “Where You Can Find More Information.”

This prospectus and any accompanying prospectus supplement do not contain all of the information included in the Registration Statement as permitted by the rules and regulations of the SEC. For further information, we refer you to the Registration Statement, including its exhibits. Statements contained in this prospectus and any accompanying prospectus supplement about the provisions or contents of any agreement or other document are not necessarily complete. If the SEC’s rules and regulations require that such agreement or document be filed as an exhibit to the Registration Statement, please see such agreement or document for a complete description of these matters. You should not assume that the information in this prospectus or any prospectus supplement is accurate as of any date other than the date on the front of each document.

FORWARD-LOOKING STATEMENTS

This prospectus and the documents incorporated by reference in this prospectus include forward-looking statements as defined in the Private Securities Litigation Reform Act of 1995. All statements regarding Comerica’s expected financial position, strategies and growth prospects and general economic conditions Comerica expects to exist in the future are forward-looking statements. Words such as “anticipates,” “believes,” “contemplates,” “feels,” “expects,” “estimates,” “seeks,” “strives,” “plans,” “intends,” “outlook,” “forecast,” “position,” “target,” “mission,” “assume,” “achievable,” “potential,” “strategy,” “goal,” “aspiration,” “opportunity,” “initiative,” “outcome,” “continue,” “remain,” “maintain,” “on track,” “trend,” “objective,” “looks forward,” “projects,” “models,” and variations of such words and similar expressions, or future or conditional verbs such as “will,” “would,” “should,” “could,” “might,” “can,” “may” or similar expressions, as they relate to Comerica or its management, are intended to identify forward-looking statements. These forward-looking statements are predicated on the beliefs and assumptions of Comerica’s management based on information known to Comerica’s management as of the date of this prospectus and do not purport to speak as of any other date. Forward-looking statements may include descriptions of plans and objectives of Comerica’s management for future or past operations, products or services, including the Growth in Efficiency and Revenue initiative (“GEAR Up”), and forecasts of Comerica’s revenue, earnings or other measures of economic performance, including statements of profitability, business segments and subsidiaries, as well as estimates of the economic benefits of the GEAR Up initiative, estimates of credit trends and global stability. Such statements reflect the view of Comerica’s management as of this date with respect to future events and are subject to risks and uncertainties. Should one or more of these risks materialize or should underlying beliefs or assumptions prove incorrect, Comerica’s actual results could differ materially from those discussed.

Factors that could cause or contribute to such differences are changes in general economic, political or industry conditions; changes in monetary and fiscal policies; whether Comerica may achieve opportunities for revenue enhancements and efficiency improvements under the GEAR Up initiative, or changes in the scope or assumptions underlying the GEAR Up initiative; operational difficulties, failure of technology infrastructure or information security incidents; reliance on other companies to provide certain key components of business infrastructure; Comerica’s ability to maintain adequate sources of funding and liquidity; the effects of more stringent capital or liquidity requirements; declines or other changes in the businesses or industries of Comerica’s

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customers; unfavorable developments concerning credit quality; changes in regulation or oversight; changes in the financial markets, including fluctuations in interest rates and their impact on deposit pricing; transitions away from LIBOR towards new interest rate benchmarks; reductions in Comerica’s credit rating; damage to Comerica’s reputation; Comerica’s ability to utilize technology to efficiently and effectively develop, market and deliver new products and services; competitive product and pricing pressures among financial institutions within Comerica’s markets; the interdependence of financial service companies; the implementation of Comerica’s strategies and business initiatives; changes in customer behavior; management’s ability to maintain and expand customer relationships; the effectiveness of methods of reducing risk exposures; the effects of catastrophic events including, but not limited to, hurricanes, tornadoes, earthquakes, fires, droughts and floods; the effects of recent tax reform and potential legislative, administrative or judicial changes or interpretations related to these and other tax regulations; any future strategic acquisitions or divestitures; management’s ability to retain key officers and employees; the impact of legal and regulatory proceedings or determinations; the effects of terrorist activities and other hostilities; changes in accounting standards; the critical nature of Comerica’s accounting policies and the volatility of Comerica’s stock price.

Comerica cautions that the foregoing list of factors is notall-inclusive. For discussion of factors that may cause actual results to differ from expectations, please refer to Comerica’s filings with the SEC. Forward-looking statements speak only as of the date they are made. Comerica does not undertake to update forward-looking statements to reflect facts, circumstances, assumptions or events that occur after the date the forward-looking statements are made, except as required by law. For any forward-looking statements made in this prospectus or the documents incorporated by reference, Comerica claims the protection of the safe harbor for forward-looking statements contained in the Private Securities Litigation Reform Act of 1995.

COMERICA INCORPORATED

Comerica Incorporated is a financial services company, incorporated under the laws of the State of Delaware, and headquartered in Dallas, Texas. Based on total assets as reported in the most recently filed Consolidated Financial Statements for Bank Holding Companies (FRY-9C), it was among the 25 largest commercial United States (“U.S.”) financial holding companies. Comerica Incorporated was formed in 1973 to acquire the outstanding common stock of Comerica Bank, which at such time was a Michigan banking corporation and one of Michigan’s oldest banks (formerly Comerica Bank-Detroit). As of December 31, 2017, Comerica Incorporated owned directly or indirectly all the outstanding common stock of 2 banking and 39non-banking subsidiaries. At December 31, 2017, Comerica Incorporated had total assets of approximately $71.6 billion, total deposits of approximately $57.9 billion, total loans (net of unearned income) of approximately $49.2 billion and shareholders’ equity of approximately $8.0 billion.

Comerica’s principal executive office is at Comerica Bank Tower, 1717 Main Street, Dallas, Texas 75201, and its telephone number is(214) 462-6831.

RISK FACTORS

Investing in our securities involves certain risks. Before you invest in any of our securities, in addition to the other information included in, or incorporated by reference into, this prospectus, you should carefully consider the risk factors contained in Item 1A under the caption “Risk Factors” and elsewhere in our annual report on Form10-K for the fiscal year ended December 31, 2017, which is incorporated into this prospectus by reference, as updated by our annual or quarterly reports for subsequent fiscal years or fiscal quarters that we file with the SEC and that are so incorporated. See “Where You Can Find More Information” for information about how to obtain a copy of these documents. You should also carefully consider the risks and other information that may be contained in, or incorporated by reference into, any prospectus supplement relating to specific offerings of securities.

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USE OF PROCEEDS

Comerica intends to use the net proceeds from the sale of any securities offered under this prospectus in the manner and for the purposes set forth in the applicable prospectus supplement.

CONSOLIDATED RATIO OF EARNINGS TO FIXED CHARGES

	Year Ended December 31,
	2017		2016		2015		2014		2013
Consolidated ratio of earnings to fixed charges:
Excluding interest on deposits		13.03x		7.94x		10.87x		12.42x		10.73x
Including interest on deposits		9.53x		5.94x		7.31x		8.21x		6.81x

For purposes of computing this ratio, earnings represent income before income taxes and fixed charges, and after interest and penalties on tax liabilities. Fixed charges include interest, whether expensed or capitalized, and that portion of rental expense deemed representative of the interest factor.

If we offer preferred stock under this prospectus, then we will, if required at that time, provide a ratio of combined fixed charges and preference dividends to earnings in the applicable prospectus supplement for such offering.

DESCRIPTION OF CAPITAL STOCK

General

As of the date of this prospectus, Comerica’s authorized capital stock consists of 325,000,000 shares of common stock, par value $5.00 per share, and 10,000,000 shares of preferred stock, without value. The following briefly summarizes the material terms of Comerica’s common stock and outstanding preferred stock. You should read the more detailed provisions of Comerica’s certificate of incorporation and the certificate of designation relating to a series of preferred stock for provisions that may be important to you.

Common Stock

As of February 9, 2018, Comerica had outstanding 172,813,294 shares of its common stock and two series of warrants, which we refer to as the Comerica Warrants and the Sterling Warrants, to purchase 874,433 shares and 31,761 shares, respectively, of Comerica’s common stock. The Comerica Warrants were issued on November 14, 2008, have10-year terms and are immediately exercisable, with an exercise price, subject to certain anti-dilution and other adjustments, equal to $29.40 per share of common stock. The Sterling Warrants were issued on December 12, 2008, have10-year terms and are immediately exercisable, with an effective exercise price, subject to certain anti-dilution and other adjustments, equal to $29.85 per share of common stock. In addition, as of February 9, 2018, approximately 4,992,920 shares of Comerica common stock were reserved for issuance upon conversion or exercise of outstanding stock options, performance restricted stock unit awards and restricted stock unit awards, and payment of deferred compensation benefits.

Subject to applicable regulatory requirements, holders of Comerica common stock are entitled to receive dividends when, as and if declared by the Comerica board of directors out of any funds legally available for dividends. Holders of Comerica common stock are also entitled, upon the liquidation of Comerica, and after claims of creditors and preferences of Comerica preferred stock, and any other class or series of Comerica preferred stock outstanding at the time of liquidation, to receive pro rata the net assets of Comerica. Comerica pays dividends on Comerica common stock only if it has paid or provided for all dividends on the outstanding series of Comerica preferred stock, and any other class or series of preferred stock at the time outstanding, for the then-current period and, in the case of any cumulative Comerica preferred stock, all prior periods.

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Comerica preferred stock has, or upon issuance will have, preference over Comerica common stock with respect to the payment of dividends and the distribution of assets in the event of the liquidation or dissolution of Comerica. Comerica preferred stock also has such other preferences as may be fixed by the Comerica board of directors.

Holders of Comerica common stock are entitled to one vote for each share that they hold and are vested with all of the voting power except as the Comerica board of directors has provided, or may provide in the future, with respect to Comerica preferred stock or any other class or series of Comerica preferred stock that it may authorize in the future. See “—Preferred Stock.” Shares of Comerica common stock are not redeemable and have no subscription, conversion or preemptive rights.

Comerica common stock is listed on the New York Stock Exchange under the symbol “CMA.” The outstanding shares of Comerica common stock are, and any shares to be issued pursuant to a prospectus supplement will be, validly issued, fully paid andnon-assessable.

The Transfer Agent and Registrar for Comerica common stock is Equiniti Trust Company, P.O. Box 64854, St. Paul, Minnesota 55164-0854.

Delaware General Corporation Law section 203 prohibits a Delaware corporation from engaging in a “business combination” (as defined in the Delaware General Corporation Law) with a person owning 15% or more of a corporation’s voting stock for three years following the time that person becomes a 15% stockholder, with certain exceptions. Comerica has not opted out of § 203 and is therefore governed by the default terms of this provision of the Delaware General Corporation Law.

The Change in Bank Control Act of 1978, as amended, prohibits a person or group of persons from acquiring “control” of a bank holding company unless the Federal Reserve Board has been notified and has not objected to the transaction. Under a rebuttable presumption established by the Federal Reserve Board, the acquisition of 10% or more of a class of voting stock of a bank holding company with a class of securities registered under Section 12 of the Exchange Act, such as Comerica, would, under the circumstances set forth in the presumption, constitute acquisition of control of the bank holding company.

In addition, a company is required to obtain the approval of the Federal Reserve Board under the Bank Holding Company Act of 1956 before acquiring 25% (5% in the case of an acquiror that is a bank holding company) or more of any class of outstanding voting stock of a bank holding company, or otherwise obtaining control or a “controlling influence” over that bank holding company.

Preferred Stock

The following briefly summarizes the material terms of Comerica’s preferred stock, other than pricing and related terms disclosed in the accompanying prospectus supplement. You should read the particular terms of any series of preferred stock offered by Comerica, which will be described in more detail in any prospectus supplement relating to such series, together with the more detailed provisions of Comerica’s certificate of incorporation and the certificate of designation relating to each particular series of preferred stock for provisions that may be important to you. The certificate of incorporation, as amended and restated, is incorporated by reference as an exhibit to the Registration Statement. The certificate of designation relating to the particular series of preferred stock offered by the accompanying prospectus supplement and this prospectus will be filed as an exhibit to a document incorporated by reference in the Registration Statement. The prospectus supplement will also state whether any of the terms summarized below do not apply to the series of preferred stock being offered.

Under Comerica’s certificate of incorporation, the board of directors of Comerica is authorized to issue up 10,000,000 shares of preferred stock in one or more series. As of the date of this prospectus, Comerica has no

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outstanding shares of preferred stock. Comerica’s Board of Directors is expressly authorized to provide for the issuance of shares of preferred stock in one or more series, with such voting powers, full or limited but not to exceed one vote per share, or without voting powers, and with such designations, preferences and relative, participating, optional or other special rights, and qualifications, limitations or restrictions thereof, as the Board of Directors may determine.

Prior to the issuance of any series of preferred stock, the board of directors of Comerica will adopt resolutions creating and designating the series as a series of preferred stock, and the resolutions will be filed in a certificate of designation as an amendment to the certificate of incorporation. The term “board of directors of Comerica” includes any duly authorized committee.

The rights of holders of the preferred stock offered may be adversely affected by the rights of holders of any shares of preferred stock that may be issued in the future. The board of directors may cause shares of preferred stock to be issued in public or private transactions for any proper corporate purpose. Examples of proper corporate purposes include issuances to obtain additional financing in connection with acquisitions or otherwise and issuances to officers, directors and employees of Comerica and its subsidiaries pursuant to benefit plans or otherwise. Shares of preferred stock issued by Comerica may have the effect of rendering more difficult or discouraging an acquisition of Comerica deemed undesirable by the board of directors of Comerica.

Under existing interpretations of the Board of Governors of the Federal Reserve System, if the holders of the preferred stock become entitled to vote for the election of directors because dividends on the preferred stock are in arrears as described below, preferred stock may then be deemed a “class of voting securities,” and a holder of 25% or more of the preferred stock or a holder of 5% or more of the preferred stock that is otherwise a bank holding company may then be regulated as a “bank holding company” with respect to Comerica in accordance with the Bank Holding Company Act. In addition, at such time:

• any bank holding company or foreign bank with a U.S. presence generally would be required to obtain the approval of the Federal Reserve Board under the Bank Holding Company of 1956 to acquire or retain 5% or more of the preferred stock; and

• any person other than a bank holding company may be required to obtain the approval of the Federal Reserve Board under the Change in Bank Control Act to acquire or retain 10% or more of the preferred stock.

Before exercising its option to redeem any shares of preferred stock, Comerica will obtain the approval of the Federal Reserve Board if then required by applicable law.

The preferred stock will be, when issued, fully paid andnon-assessable. Holders of preferred stock will not have any preemptive or subscription rights to acquire more stock of Comerica.

The transfer agent, registrar, dividend disbursing agent and redemption agent for shares of each series of preferred stock will be named in the prospectus supplement relating to such series.

Rank

Unless otherwise specified in connection with a particular offering of preferred stock, such shares will rank on an equal basis with each other series of preferred stock and prior to the common stock as to dividends and distributions of assets.

Dividends

Subject to applicable regulatory requirements, holders of each series of preferred stock will be entitled to receive cash dividends when, as and if declared by the board of directors of Comerica out of funds legally available for

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dividends. The rates and dates of payment of dividends will be set forth in the prospectus supplement relating to each series of preferred stock. Dividends will be payable to holders of record of preferred stock as they appear on the books of Comerica or, if applicable, the records of the depositary referred to below under “Description of Depositary Shares,” on the record dates fixed by the board of directors. Dividends on a series of preferred stock may be cumulative or noncumulative.

Comerica may not declare, pay or set apart for payment dividends on the preferred stock unless full dividends on other series of preferred stock that rank on an equal or senior basis have been paid or sufficient funds have been set apart for payment for

• all prior dividend periods of other series of preferred stock that pay dividends on a cumulative basis; or

• the immediately preceding dividend period of other series of preferred stock that pay dividends on a noncumulative basis.

Partial dividends declared on shares of preferred stock and each other series of preferred stock ranking on an equal basis as to dividends will be declared pro rata. A pro rata declaration means that the ratio of dividends declared per share to accrued dividends per share will be the same for each series of preferred stock.

Similarly, Comerica may not declare, pay or set apart for paymentnon-stock dividends or make other payments on the common stock or any other stock of Comerica ranking junior to the preferred stock until full dividends on the preferred stock have been paid or set apart for payment for

• all prior dividend periods if the preferred stock pays dividends on a cumulative basis; or

• the immediately preceding dividend period if the preferred stock pays dividends on a noncumulative basis.

Conversion and Exchange

The prospectus supplement for a series of preferred stock will state the terms, if any, on which shares of that series are convertible into or exchangeable for shares of Comerica’s common stock.

Redemption

If so specified in the applicable prospectus supplement, a series of preferred stock may be redeemable at any time, in whole or in part, at the option of Comerica or the holder thereof and may be mandatorily redeemed.

Any partial redemptions of preferred stock will be made in a way that the board of directors decides is equitable.

Unless Comerica defaults in the payment of the redemption price, dividends will cease to accrue after the redemption date on shares of preferred stock called for redemption, and all rights of holders of such shares will terminate except for the right to receive the redemption price.

Liquidation Preference

Upon any voluntary or involuntary liquidation, dissolution or winding up of Comerica, holders of each series of preferred stock will be entitled to receive distributions upon liquidation in the amount set forth in the prospectus supplement relating to such series of preferred stock, plus an amount equal to any accrued and unpaid dividends. Such distributions will be made before any distribution is made on any securities ranking junior relating to liquidation, including common stock.

If the liquidation amounts payable relating to the preferred stock of any series and any other securities ranking on a parity regarding liquidation rights are not paid in full, the holders of the preferred stock of such series and such

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other securities will share in any such distribution of available assets of Comerica on a ratable basis in proportion to the full liquidation preferences. Holders of such series of preferred stock will not be entitled to any other amounts from Comerica after they have received their full liquidation preference.

Voting Rights

The holders of shares of preferred stock will have no voting rights except:

• as otherwise stated in the prospectus supplement;

• as otherwise stated in the certificate of designation establishing such series; and

• as required by applicable law.

DESCRIPTION OF DEPOSITARY SHARES

The following briefly summarizes the material provisions of the deposit agreement and of the depositary shares and depositary receipts, other than pricing and related terms disclosed in the accompanying prospectus supplement. You should read the particular terms of any depositary shares and any depositary receipts that are offered by Comerica and any deposit agreement relating to a particular series of preferred stock, which will be described in more detail in a prospectus supplement. The prospectus supplement will also state whether any of the generalized provisions summarized below do not apply to the depositary shares or depositary receipts being offered. A copy of the form of deposit agreement, including the form of depositary receipt, is incorporated by reference as an exhibit to the Registration Statement. You should read the more detailed provisions of the deposit agreement and the form of depositary receipt for provisions that may be important to you.

General

Comerica may, at its option, elect to offer fractional shares of preferred stock, rather than full shares of preferred stock. In such event, Comerica will issue receipts for depositary shares, each of which will represent a fraction of a share of a particular series of preferred stock.

The shares of any series of preferred stock represented by depositary shares will be deposited under a deposit agreement between Comerica and a bank or trust company selected by Comerica having its principal office in the United States and having a combined capital and surplus of at least $50,000,000, as preferred stock depositary. Each owner of a depositary share will be entitled to all the rights and preferences of the underlying preferred stock, including dividend, voting, redemption, conversion and liquidation rights, in proportion to the applicable fraction of a share of preferred stock represented by such depositary share.

The depositary shares will be evidenced by depositary receipts issued pursuant to the deposit agreement. Depositary receipts will be distributed to those persons purchasing the fractional shares of preferred stock in accordance with the terms of the applicable prospectus supplement.

Dividends and Other Distributions

The preferred stock depositary will distribute all cash dividends or other cash distributions received in respect of the deposited preferred stock to the record holders of depositary shares relating to such preferred stock in proportion to the number of such depositary shares owned by such holders.

The preferred stock depositary will distribute any property received by it other than cash to the record holders of depositary shares entitled thereto. If the preferred stock depositary determines that it is not feasible to make such distribution, it may, with the approval of Comerica, sell such property and distribute the net proceeds from such sale to such holders.

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Redemption of Preferred Stock

If a series of preferred stock represented by depositary shares is to be redeemed, the depositary shares will be redeemed from the proceeds received by the preferred stock depositary resulting from the redemption, in whole or in part, of such series of preferred stock. The depositary shares will be redeemed by the preferred stock depositary at a price per depositary share equal to the applicable fraction of the redemption price per share payable in respect of the shares of preferred stock so redeemed.

Whenever Comerica redeems shares of preferred stock held by the preferred stock depositary, the preferred stock depositary will redeem as of the same date the number of depositary shares representing the shares of preferred stock so redeemed. If fewer than all the depositary shares are to be redeemed, the depositary shares to be redeemed will be selected by the preferred stock depositary by lot or ratably or by any other equitable method as the preferred stock depositary may decide.

Withdrawal of Preferred Stock

Unless the related depositary shares have previously been called for redemption, any holder of depositary shares may receive the number of whole shares of the related series of preferred stock and any money or other property represented by such depositary receipts after surrendering the depositary receipts at the corporate trust office of the preferred stock depositary. Holders of depositary shares making such withdrawals will be entitled to receive whole shares of preferred stock on the basis set forth in the related prospectus supplement for such series of preferred stock.

However, holders of such whole shares of preferred stock will not be entitled to deposit such preferred stock under the deposit agreement or to receive depositary receipts for such preferred stock after such withdrawal. If the depositary shares surrendered by the holder in connection with such withdrawal exceed the number of depositary shares that represent the number of whole shares of preferred stock to be withdrawn, the preferred stock depositary will deliver to such holder at the same time a new depositary receipt evidencing such excess number of depositary shares.

Voting Deposited Preferred Stock

Upon receipt of notice of any meeting at which the holders of any series of deposited preferred stock are entitled to vote, the preferred stock depositary will mail the information contained in such notice of meeting to the record holders of the depositary shares relating to such series of preferred stock. Each record holder of such depositary shares on the record date will be entitled to instruct the preferred stock depositary to vote the amount of the preferred stock represented by such holder’s depositary shares. The preferred stock depositary will try to vote the amount of such series of preferred stock represented by such depositary shares in accordance with such instructions.

Comerica will agree to take all reasonable actions that the preferred stock depositary determines are necessary to enable the preferred stock depositary to vote as instructed. The preferred stock depositary will vote all shares of any series of preferred stock held by it proportionately with instructions received if it does not receive specific instructions from the holders of depositary shares representing such series of preferred stock.

Amendment and Termination of the Deposit Agreement

The form of depositary receipt evidencing the depositary shares and any provision of the deposit agreement may at any time be amended by agreement between Comerica and the preferred stock depositary. However, any amendment that imposes additional charges or materially and adversely alters any substantial existing right of the holders of depositary shares will not be effective unless such amendment has been approved by the holders of at least a majority of the affected depositary shares then outstanding. Every holder of an outstanding depositary

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receipt at the time any such amendment becomes effective, or any transferee of such holder, shall be deemed, by continuing to hold such depositary receipt, or by reason of the acquisition thereof, to consent and agree to such amendment and to be bound by the deposit agreement, that has been amended thereby. The deposit agreement automatically terminates if:

• all outstanding depositary shares have been redeemed;

• each share of preferred stock has been converted into or exchanged for common stock; or

• a final distribution in respect of the preferred stock has been made to the holders of depositary shares in connection with any liquidation, dissolution or winding up of Comerica.

The deposit agreement may be terminated by Comerica at any time, and the preferred stock depositary will give notice of such termination to the record holders of all outstanding depositary receipts not less than 30 days prior to the termination date. In such event, the preferred stock depositary will deliver or make available for delivery to holders of depositary shares, upon surrender of such depositary shares, the number of whole or fractional shares of the related series of preferred stock as are represented by such depositary shares.

Charges of Preferred Stock Depositary; Taxes and Other Governmental Charges

No fees, charges and expenses of the preferred stock depositary or any agent of the preferred stock depositary or of any registrar shall be payable by any person other than Comerica, except for any taxes and other governmental charges and except as provided in the deposit agreement. If the preferred stock depositary incurs fees, charges or expenses for which it is not otherwise liable hereunder at the election of a holder of a depositary receipt or other person, such holder or other person will be liable for such fees, charges and expenses.

Resignation and Removal of Depositary

The preferred stock depositary may resign at any time by delivering to Comerica notice of its intent to do so, and Comerica may at any time remove the preferred stock depositary, any such resignation or removal to take effect upon the appointment of a successor preferred stock depositary and its acceptance of such appointment. Such successor preferred stock depositary must be appointed within 60 days after delivery of the notice of resignation or removal and must be a bank or trust company having its principal office in the United States and having a combined capital and surplus of at least $50,000,000.

Miscellaneous

The preferred stock depositary will forward all reports and communications from Comerica that are delivered to the preferred stock depositary and that Comerica is required to furnish to the holders of the deposited preferred stock.

Neither the preferred stock depositary nor Comerica will be liable if it is prevented or delayed by law or any circumstances beyond its control in performing its obligations under the deposit agreement. The obligations of Comerica and the preferred stock depositary under the deposit agreement will be limited to performance with honest intentions of their duties thereunder, and they will not be obligated to prosecute or defend any legal proceeding in respect of any depositary shares, depositary receipts or shares of preferred stock unless satisfactory indemnity is furnished. Comerica and the preferred stock depositary may rely upon written advice of counsel or accountants or upon information provided by holders of depositary receipts or other persons believed to be competent and on documents believed to be genuine.

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DESCRIPTION OF DEBT SECURITIES

The following description of the debt securities sets forth the material terms and provisions of the debt securities. The debt securities offered by this prospectus will be unsecured obligations of Comerica and will be either senior or subordinated debt. The senior debt securities will be issued under an indenture (the “senior indenture”), between Comerica and The Bank of New York Mellon Trust Company, N.A., dated as of May 23, 2014, a copy of which is incorporated by reference as an exhibit to the Registration Statement of which this prospectus forms a part. The subordinated debt securities will be issued under an indenture (the “subordinated indenture”), between Comerica and The Bank of New York Mellon Trust Company, N.A., as successor trustee, dated as of May 1, 2003, a copy of which is incorporated by reference as an exhibit to the Registration Statement of which this prospectus forms a part. The senior indenture and the subordinated indenture are referred to in this prospectus collectively as the “indentures” and each individually as an “indenture.” The specific terms applicable to a particular issuance of debt securities and any variations from the terms set forth below will be set forth in the applicable prospectus supplement.

The following is a summary of the material terms and provisions of the indentures and the debt securities. You should refer to the indentures and the debt securities for complete information regarding the terms and provisions of the indentures and the debt securities. The indentures are substantially identical, except for the covenants of and provisions relating to subordination.

General

The indentures do not limit the aggregate principal amount of debt securities which Comerica may issue and provide that Comerica may issue debt securities under the indentures from time to time in one or more series. Comerica may from time to time, without giving notice to or seeking the consent of the holders of the debt securities of any series, issue debt securities having the same ranking and the same terms (other than the public offering price, issue date, payment of interest accruing prior to the issue date and, under some circumstances, the first interest payment date) as the debt securities of a previously issued series. Any additional debt securities having such identical terms, together with the debt securities of the applicable series previously issued, will constitute a single series of debt securities under the indenture. The indentures do not limit the amount of other indebtedness, or debt securities other than secured indebtedness, which Comerica or its subsidiaries may issue.

Unless otherwise provided in a prospectus supplement, the senior debt securities will be Comerica’s unsecured obligations and will rank equally with all of its other unsecured and unsubordinated indebtedness from time to time outstanding. The subordinated debt securities will be Comerica’s unsecured obligations and will be subordinated in right of payment to the prior payment in full of all of Comerica’s senior indebtedness, which term includes senior debt securities, as described below under “—Subordination.” In certain events of insolvency, the subordinated debt securities will also be subordinated to certain other financial obligations, as described below under “—Subordination.”

Because Comerica is a holding company, its rights and the rights of its creditors, including holders of debt securities, and shareholders to participate in any distribution of assets of any subsidiary upon the subsidiary’s liquidation or reorganization or otherwise would be subject to the prior claims of the subsidiary’s creditors, except to the extent that Comerica is a creditor of the subsidiary. The right of Comerica’s creditors, including holders of debt securities, to participate in the distribution of stock owned by Comerica in some of its subsidiaries, including its banking subsidiaries, may also be subject to approval by bank regulatory authorities having jurisdiction over these subsidiaries.

Each prospectus supplement will describe the following terms of the offered debt securities:

• the title of the series;

• any limit on the aggregate principal amount;

• the principal payment dates;

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• the interest rates, if any, which rate may be zero if the debt securities are issued at a discount from the principal amount payable at maturity, or the method by which the interest rates will be determined, including, if applicable, any remarketing option or similar method;

• the date or dates from which interest, if any, will accrue or the method by which the date or dates will be determined;

• the interest payment dates and regular record dates;

• the place or places where the principal of, any premium or interest on any debt securities will be payable, where any of debt securities may be surrendered for registration of transfer or exchange, and where any debt securities may be surrendered for conversion or exchange;

• whether any of the debt securities are to be redeemable at Comerica’s option and, if so, the date or dates on which, the period or periods within which, the price or prices at which and the other terms and conditions upon which they may be redeemed, in whole or in part;

• whether Comerica will be obligated to redeem or purchase any of the debt securities pursuant to any sinking fund or analogous provision or at the holder’s option, and, if so, the dates or prices and the other terms on which the debt securities must be redeemed or purchased pursuant to this obligation and any provisions for the remarketing of the debt securities so redeemed or purchased;

• if other than denominations of $2,000 and any integral multiple of $1,000, the denominations in which any debt securities will be issuable;

• whether the debt securities will be convertible into Comerica common or preferred stock and/or exchangeable for other securities, whether or not issued by Comerica and, if so, the terms and conditions upon which the debt securities will be convertible or exchangeable;

• if other than the principal amount, the portion of the principal amount, or the method by which the portion will be determined, of the debt securities that will be payable upon declaration of acceleration of the maturity of the debt securities;

• if other than United States dollars, the currency of payment in which the principal of, any premium or interest on the debt securities will be paid;

• whether the principal of, any premium or interest on the debt securities will be payable, at Comerica’s or the holder’s election, in a currency other than that in which the debt securities are stated to be payable, and the dates and the other terms upon which this election may be made;

• any index, formula or other method used to determine the amount of principal of, any premium or interest on the debt securities;

• whether the debt securities are to be issued in the form of one or more global securities and, if so, the identity of the depositary for the global security or securities;

• whether the debt securities are senior or subordinated and, if subordinated, the applicable subordination provisions;

• in the case of subordinated debt securities, the relative degree, if any, to which the subordinated debt securities will be senior to or be subordinated to other series of subordinated debt securities or other indebtedness of Comerica in right of payment, whether the other series of subordinated debt securities or other indebtedness is outstanding or not;

• any deletions from, modifications of or additions to the events of default or covenants of Comerica, and any change in the right of the trustee or the holders to declare the principal, premium and interest with respect to the debt securities due and payable;

• whether the provisions described below under “—Discharge, Defeasance and Covenant Defeasance” will be applicable to the debt securities;

• whether any of the debt securities are to be issued upon the exercise of warrants and the time, manner and place for the debt securities to be authenticated and delivered; and

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• any other terms of the debt securities and any other deletions from or modifications or additions to the applicable indenture.

Unless otherwise set forth in the applicable prospectus supplement, Comerica will only issue the debt securities in fully registered form without coupons.

Unless otherwise set forth in the applicable prospectus supplement, principal of, premium and interest on the debt securities will initially be payable at the corporate trust office of the trustee.

Interest on debt securities may be paid by check mailed to the persons entitled to the payments at their addresses appearing on the security register or by transfer to an account maintained by the payee with a bank located in the United States and will be payable on any interest payment date to the persons in whose names the debt securities are registered at the close of business on the regular record date with respect to the interest payment date.

Unless otherwise set forth in the applicable prospectus supplement, the trustee will act as the paying agent. Comerica may designate additional paying agents, rescind the designation of any paying agent or approve a change in the office through which any paying agent acts.

Unless otherwise set forth in the applicable prospectus supplement, holders may present the debt securities for transfer, duly endorsed or accompanied by a written instrument of transfer if so required by Comerica or the security registrar, or exchange for other debt securities of the same series containing identical terms and provisions, in any authorized denominations, and of a like aggregate principal amount, in each case at the office or agency maintained by Comerica for this purpose, which will initially be the corporate trust office of the trustee. Any transfer or exchange will be made without service charge, although Comerica may require payment of a sum sufficient to cover any tax or other governmental charge and any other expenses then payable. Comerica is not required to issue, register the transfer of, or exchange debt securities during a period beginning at the opening of business 15 days before the day of mailing of a notice of redemption of any debt securities and ending at the close of business on the day of mailing or register the transfer of or exchange any debt security selected for redemption, in whole or in part, except the unredeemed portion of any debt security being redeemed in part.

The debt securities may be issued as original issue discount securities, which means that they will bear no interest or bear interest at a rate which, at the time of issuance, is below market rates. Debt securities issued as original issue discount securities will be sold at a substantial discount below their principal amount. U.S. Federal income tax and other considerations applicable to original issue discount securities will be described in the applicable prospectus supplement.

If the purchase price, or the principal of, or any premium or interest on, any debt securities is payable in, or if any debt securities are denominated in, one or more foreign currencies or currency units, the restrictions, elections, U.S. Federal income tax considerations, specific terms and other information will be set forth in the applicable prospectus supplement.

Conversion and Exchange

The terms, if any, on which debt securities are convertible into or exchangeable for, either mandatorily or at Comerica’s or the holder’s option, property or cash, common stock, preferred stock or other securities, whether or not issued by Comerica, or a combination of any of these, will be set forth in the applicable prospectus supplement.

Global Securities

The debt securities may be issued, in whole or in part, in the form of one or more global securities that will be deposited with, or on behalf of, a depositary identified in the applicable prospectus supplement and registered in

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the name of the depositary or its nominee. Interests in any global debt security will be shown on, and transfers of the debt securities will be effected only through, records maintained by the depositary and its participants. The specific terms of the depositary arrangement will be described in the applicable prospectus supplement.

Subordination

Under the subordinated debt indenture, payment of the principal, interest and any premium on the subordinated debt securities will generally be subordinated and junior in right of payment to the prior payment in full of all Senior Indebtedness (as defined below). The subordinated debt indenture provides that no payment of principal, interest or any premium on the subordinated debt securities may be made unless we pay in full the principal, interest, any premium or any other amounts on any Senior Indebtedness then due. Also, no payment of principal, interest or any premium on the subordinated debt securities may be made if there shall have occurred and be continuing an event of default with respect to any Senior Indebtedness permitting the holders thereof to accelerate the maturity thereof, or if any judicial proceeding shall be pending with respect to any such default.

If there is any insolvency, bankruptcy, liquidation or other similar proceeding relating to Comerica, then all Senior Indebtedness must be paid in full before any payment may be made to any holders of subordinated debt securities. If after payment of the Senior Indebtedness there remains any amounts available for distribution and any person entitled to payment pursuant to the terms of Other Financial Obligations (as defined below) has not been paid in full all amounts due or to become due on the Other Financial Obligations, then these remaining amounts shall first be used to pay in full the Other Financial Obligations before any payment may be made to the holders of subordinated debt securities. Holders of subordinated debt securities must deliver any payments received by them to the trustee in bankruptcy or other person making payment or distribution of the assets of Comerica for application to the payment of all Senior Indebtedness and Other Financial Obligations remaining unpaid until all Senior Indebtedness and Other Financial Obligations are paid in full.

The subordinated debt indenture does not limit the amount of Senior Indebtedness and Other Financial Obligations that Comerica may incur. “Senior Indebtedness” means any of the following, whether incurred before or after the execution of the subordinated debt indenture:

(1) all obligations of ours for the repayment of borrowed or purchased money,

(2) all obligations of ours for the deferred purchase price of property,

(3) all of our capital lease obligations, and

(4) all obligations of the type referred to in clauses (1) through (3) of other persons that Comerica has guaranteed or that is otherwise Comerica’s legal liability;

but Senior Indebtedness does not include the subordinated debt securities or indebtedness that by its terms is subordinated to, or ranks on an equal basis with, the subordinated debt securities.

“Other Financial Obligations” means all obligations of Comerica to make payment pursuant to the terms of financial instruments, such as:

(1) securities contracts and foreign currency exchange contracts,

(2) derivative instruments, including swap agreements, cap agreements, floor agreements, collar agreements, interest rate agreements, foreign exchange agreements, options, commodity futures contracts and commodity option contracts, and

(3) similar financial instruments;

but Other Financial Obligations does not include Senior Indebtedness or indebtedness that by its terms is subordinated to, or ranks on an equal basis with, the subordinated debt securities.

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Events of Default, Waiver

An “Event of Default” with respect to a series of debt securities is defined in the indentures as:

• default for 30 days in the payment of interest on any debt securities of that series;

• default in payment of principal or other amounts payable on any debt securities of that series when due, at maturity, upon redemption, by declaration of acceleration, or otherwise;

• default in the deposit of any sinking fund payment, when due by the terms of a series of debt securities;

• failure by Comerica for 60 days after notice to perform any other covenants or warranties contained in the Indenture applicable to that series;

• certain events of bankruptcy or reorganization of Comerica; and

• any other event of default provided in the applicable supplemental indentures or form of security.

With respect to the senior debt securities, if a default in the payment of principal, interest or other amounts payable on the senior debt securities, or in the performance of any covenant or agreement, or in a manner provided in the applicable supplemental indenture or form of security, with respect to one or more series of senior debt securities occurs and is continuing (other than a default arising out of certain events of bankruptcy or reorganization of Comerica), either the trustee or the holders of at least 25% in principal amount of the senior debt securities of such series then outstanding, treated as one class, may declare the principal of all outstanding senior debt securities of such series to be due and payable immediately. If a default arising out of certain events of bankruptcy or reorganization of Comerica occurs, the principal of all outstanding senior debt securities and any interest accrued thereon shall become due and payable immediately without any further action on the part of the trustee or the holders of the senior debt securities.

With respect to the subordinated debt securities, if a default arising out of certain events of bankruptcy or reorganization of Comerica occurs, either the trustee or the holders of at least 25% in principal amount of the subordinated debt securities of such series then outstanding, treated as one class, may declare the principal of all outstanding subordinated debt securities of such series to be due and payable immediately. The subordinated indenture does not provide for any right of acceleration of the payment of the principal of a series of subordinated debt securities upon a default in the payment of principal, premium, if any, or interest or a default in the performance of any covenant or agreement in the subordinated debt securities of that series or in the subordinated indenture. Accordingly, the trustee under the subordinated indenture and the holders will not be entitled to accelerate the maturity of those debt securities upon the occurrence of any of the events of default described above, except for those arising out of certain events of bankruptcy or reorganization of Comerica. If a default in the payment of principal, premium, if any, or interest or in the performance of any covenant or agreement in the subordinated debt securities of any series or in the subordinated indenture occurs, the trustee under the subordinated indenture may, subject to certain limitations and conditions, seek to enforce payment of such principal, premium, if any, or interest on the subordinated debt securities of that series, or the performance of such covenant or agreement.

In the case of original issue discount securities, only a specified portion of the principal amount may be accelerated.

Subject to certain conditions such declarations may be annulled and past defaults, except for uncured payment defaults on the debt securities, may be waived by the holders of a majority in principal amount of the outstanding debt securities of the series affected. An Event of Default with respect to one series of debt securities does not necessarily constitute an Event of Default with respect to any other series of debt securities. The indentures provide that the trustee may withhold notice to the holders of the debt securities of any default if the trustee considers it in the interest of the holders of the debt securities to do so. The trustee may not withhold notice of a default in the payment of principal of, interest on or any other amounts due under, such debt securities.

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The indentures provide that the holders of a majority in principal amount of outstanding debt securities of any series may direct the time, method, and place of conducting any proceeding for any remedy available to the trustee, or exercising any trust or other power conferred on the trustee. The trustee may decline to act if the direction is contrary to law and in certain other circumstances set forth in the applicable indenture. The trustee is not obligated to exercise any of its rights or powers under the applicable indenture at the request or direction of the holders of debt securities unless the holders offer the trustee indemnity satisfactory to it (in the case of the senior indenture) or reasonable indemnity (in the case of the subordinated indenture) against expenses and liabilities.

No holder of any debt security of any series has the right to institute any action for remedy unless such holder has previously given to the trustee written notice of default, the trustee has failed to take action for 60 days after the holders of not less than 25% in principal amount of the debt securities of such series make written request upon the trustee to institute such action and the holders offer the trustee indemnity reasonably satisfactory to it (in the case of the senior indenture) or reasonable indemnity (in the case of the subordinated indenture) against expenses and liabilities.

The indentures require Comerica to file annually with the trustee a written statement of no default, or specifying any default that exists.

Whenever the indentures provide for an action by, or the determination of any of the rights of, or any distribution to, holders of debt securities, in the absence of any provision to the contrary in the form of debt security, any amount in respect of any debt security denominated in a currency or currency unit other than U.S. dollars may be treated for any such action or distribution as the amount of U.S. dollars that could reasonably be exchanged for such non U.S. dollar amount. This amount will be calculated as of a date that Comerica specifies to the trustee or, if Comerica fails to specify a date, on a date that the trustee may determine.

Discharge, Defeasance and Covenant Defeasance

Discharge of Indenture. An indenture will cease to be of further effect with respect to debt securities of any series issued thereunder, except as to rights of registration of transfer and exchange, substitution of mutilated or defaced debt securities, rights of holders to receive principal, interest or other amounts payable under the debt securities, rights and immunities of the trustee and rights of holders with respect to property deposited pursuant to the following provisions and certain obligations of, and payments to, the trustee, if at any time:

• Comerica has paid the principal, interest or other amounts payable under the debt securities of such series;

• Comerica has delivered to the trustee for cancellation all debt securities of such series; or

• the debt securities of such series not delivered to the trustee for cancellation have become due and payable, or will become due and payable within one year, or are to be called for redemption within one year under arrangements satisfactory to the trustee, and Comerica has irrevocably deposited with the trustee as trust funds the entire amount in cash or U.S. government obligations sufficient to pay all amounts due with respect to such debt securities on or after the date of such deposit, including at maturity or upon redemption of all such debt securities, including principal, interest and other amounts.

The trustee, on demand of Comerica accompanied by an Officers’ Certificate and an Opinion of Counsel and at the cost and expense of Comerica, will execute proper instruments acknowledging such satisfaction of and discharging the Indenture with respect to such series.

Defeasance of a Series of Debt Securities at Any Time. Comerica may also discharge all of its obligations, other than as to rights of registration of transfer and exchange, substitution of mutilated or defaced debt securities, rights of holders to receive principal, interest or other amounts payable under the debt securities, rights and immunities of the trustee and rights of holders with respect to property deposited pursuant to the following provisions, under any series of debt securities at any time, which is referred to as “defeasance”.

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Comerica may be released with respect to any outstanding series of debt securities from the obligations to comply with certain restrictive covenants under the applicable indenture identified in the applicable prospectus supplement, and any omission to comply with such obligations will not constitute an event of default. Discharge under these procedures is called “covenant defeasance”.

Defeasance or covenant defeasance may be effected only if, among other things:

• Comerica irrevocably deposits with the trustee cash or U.S. government obligations, as trust funds in an amount certified to be sufficient to pay on each date that they become due and payable, the principal of, interest on, other amounts due under, and any mandatory sinking fund payments for, all outstanding debt securities of the series being defeased;

• No event of default with respect to such series of debt securities has occurred and is continuing and, with respect to subordinated debt securities, no event of default with respect to Senior Indebtedness has occurred and is continuing and which permits acceleration; and

• Comerica delivers to the trustee an opinion of counsel to the effect that:

• the beneficial owners of the series of debt securities being defeased will not recognize income, gain or loss for United States federal income tax purposes as a result of the defeasance or covenant defeasance; and

• the defeasance or covenant defeasance will not otherwise alter those beneficial owners’ United States federal income tax treatment of principal or interest payments or other amounts due under the series of debt securities being defeased; and

• in the case of a defeasance, this opinion must be based on a ruling of the Internal Revenue Service or a change in United States federal income tax law occurring after the date of this prospectus, since that result would not occur under current tax law.

Modification of the Indenture; Waiver of Compliance

Each indenture contain provisions permitting Comerica and the trustee to modify the indenture or the rights of the holders of debt securities with the consent of the holders of not less than a majority in principal amount of each outstanding series of debt securities affected by the modification. Each holder of an affected debt security must consent to a modification that would:

• change the stated maturity date of the principal of, or of any installment of principal of or interest on, any debt security;

• reduce the principal amount of, interest on, or any other amounts due under any debt security;

• reduce the amount of, or postpone the date fixed for, the payment of any sinking fund payment;

• change the currency or currency unit of payment of any debt security;

• reduce the portion of the principal amount of an original issue discount security payable upon acceleration of the maturity thereof;

• reduce any amount payable upon redemption of any debt security;

• impair the right of a holder to institute suit for the payment of or, if the debt securities provide, any right of repayment at the option of the holder of a debt security;

• reduce the percentage of debt securities of any series, the consent of the holders of which is required for any waiver or modification; or

• with respect to the subordinated indenture only, modify the provisions with respect to the subordination of the subordinated debt securities in a manner adverse to the holders.

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Each indenture also permits Comerica and the trustee to amend the indenture in certain circumstances without the consent of the holders of debt securities to evidence Comerica’s merger, the replacement of the trustee, to effect changes that do not affect any outstanding series of debt security, and for certain other purposes.

Consolidations, Mergers and Sales of Assets

Comerica may not merge or consolidate with any other corporation or sell or convey all or substantially all of its assets to any other corporation, unless either:

• Comerica is the continuing corporation or the successor corporation is a corporation that expressly assumes the payment of the principal of, any interest on, or any other amounts due under the debt securities and the performance and observance of all the covenants and conditions of the indentures binding upon us, and

• Comerica or the successor corporation shall not, immediately after the merger or consolidation, sale or conveyance, be in default in the performance of any covenant or condition.

There are no covenants or other provisions in the indentures that would afford holders of debt securities additional protection in the event of a recapitalization transaction, a change of control of Comerica or a highly leveraged transaction. The merger covenant described above would only apply if the recapitalization transaction, change of control or highly leveraged transaction were structured to include a merger or consolidation of Comerica, or a sale or conveyance or lease of all or substantially all of its assets. However, Comerica may provide specific protections, such as a put right or increased interest, for particular debt securities, that Comerica would describe in the applicable prospectus supplement.

Governing Law

The indentures and debt securities will be governed by and construed in accordance with the laws of the State of New York.

DESCRIPTION OF THE WARRANTS TO PURCHASE

COMMON STOCK OR PREFERRED STOCK

The following summary sets forth the material terms and provisions of the common stock warrants and preferred stock warrants, that would be issued pursuant to a stock warrant agreement between Comerica and a stock warrant agent to be selected at the time of issue. The stock warrant agreement may include or incorporate by reference standard warrant provisions substantially in the form of provisions contained in the form of warrant agreement, which is filed as an exhibit to the Registration Statement.

General

The stock warrants may be issued under the stock warrant agreement independently or together with any other securities offered by a prospectus supplement. If stock warrants are offered, the applicable prospectus supplement will describe the designation and terms of the stock warrants, including, without limitation, the following:

• the offering price, if any;

• the designation and terms of the common stocks or preferred stocks purchasable upon exercise of the stock warrants;

• if applicable, the date on and after which the stock warrants and the related offered securities will be separately transferable;

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• the number of common stocks or preferred stocks purchasable upon exercise of one stock warrant and the initial price at which shares may be purchased upon exercise of the stock warrant;

• the date on which the right to exercise the stock warrants shall commence and the date on which these rights shall expire;

• a discussion of the material U.S. Federal income tax considerations;

• any call provisions;

• the currency in which the offering price, if any, and exercise price are payable;

• the anti-dilution provisions of the stock warrants; and

• any other terms of the stock warrants.

The shares of common stock or preferred stock issuable upon exercise of the stock warrants will, when issued in accordance with the stock warrant agreement, be fully paid andnon-assessable. This means that the shares will be paid for in full at the time they are issued, and, once they are paid for in full, there will be no further liability for further assessments or taxation.

Exercise of Stock Warrants

You may exercise your stock warrants by surrendering to the stock warrant agent your stock warrant certificate with the form of election to purchase on the reverse of the certificate properly completed and executed by you, or your authorized agent, which signature must be guaranteed by a bank or trust company, by a broker or dealer which is a member of the Financial Industry Regulatory Authority, Inc. (“FINRA”) or by a member of a national securities exchange. You must indicate on the form of election whether you are electing to exercise all or a portion of the stock warrants evidenced by the certificate. You must also submit a payment of the aggregate exercise price of the stock warrants to be exercised in lawful money of the United States along with your stock warrant certificates, unless otherwise set forth in the applicable prospectus supplement. Upon receipt of the stock warrant certificate, form of election and aggregate payment, if applicable, by the stock warrant agent, the stock warrant agent will requisition from the transfer agent for the common stocks or the preferred stocks, as the case may be, a certificate representing the number of common stocks or preferred stocks purchased for issuance and delivery to you or upon your written order. If you exercise less than all of the stock warrants evidenced by any stock warrant certificate, the stock warrant agent shall deliver to you a new stock warrant certificate representing your unexercised stock warrants.

Anti-Dilution and Other Provisions

The exercise price payable, the number of shares of common stock or preferred stock purchasable upon the exercise of each stock warrant, and the number of stock warrants outstanding are subject to adjustment if specified events occur. These events include:

• the issuance of a stock dividend to holders of shares of Comerica’s common stock or preferred stock; and

• a combination, subdivision or reclassification of Comerica’s common stock or preferred stock.

In lieu of adjusting the number of shares of common stock or preferred stock purchasable upon exercise of each stock warrant, Comerica may elect to adjust the number of stock warrants. No adjustment in the number of shares purchasable upon exercise of the stock warrants will be required until cumulative adjustments require an adjustment of at least 1% in the number of shares purchasable. Comerica may also, at its option, reduce the exercise price at any time. No fractional shares will be issued upon exercise of stock warrants, but Comerica will pay the cash value of any fractional shares otherwise issuable. Notwithstanding the preceding sentences, in case of any consolidation, merger, or sale or conveyance of Comerica’s property, Comerica in its entirety or

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substantially in its entirety, you, as a stock warrant holder, shall have the right to the kind and amount of shares of stock and other securities and property, including cash, receivable by a holder of the number of common stocks or preferred stocks into which your stock warrants were exercisable immediately prior to this event.

No Rights as Shareholders

You will not be entitled, by virtue of being a stock warrant holder, to vote, to consent, to receive dividends, to receive notice as shareholders with respect to any meeting of shareholders for the election of Comerica’s directors or any other matter, or to exercise any rights whatsoever as shareholders of Comerica.

DESCRIPTION OF THE WARRANTS TO PURCHASE DEBT SECURITIES

The following summary sets forth the material terms and provisions of the debt warrants, which would be issued pursuant to a debt warrant agreement between Comerica and a debt warrant agent to be selected at the time of issue. The debt warrant agreement may include or incorporate by reference standard warrant provisions substantially in the form of provisions contained in the form of warrant agreement, which is filed as an exhibit to the Registration Statement.

General

The debt warrants may be issued under the debt warrant agreement independently or together with any other securities offered by a prospectus supplement. If debt warrants are offered, the applicable prospectus supplement will describe the designation and terms of the debt warrants, including, without limitation, the following:

• the offering price, if any;

• the designation, aggregate principal amount and terms of the debt securities purchasable upon exercise of the debt warrants;

• if applicable, the date on and after which the debt warrants and the related offered securities will be separately transferable;

• the principal amount of debt securities purchasable upon exercise of one debt warrant and the price at which the principal amount of debt securities may be purchased upon exercise of the debt warrant;

• the date on which the right to exercise the debt warrants shall commence and the date on which this right shall expire;

• a discussion of the material U.S. Federal income tax considerations;

• whether the warrants represented by the debt warrant certificates will be issued in registered or bearer form;

• the currency, currencies or currency units in which the offering price, if any, and exercise price are payable;

• the anti-dilution provisions of the debt warrants; and

• any other terms of the debt warrants.

You, as a debt warrant holder, will generally not have any of the rights of holders of Comerica debt securities, including the right to receive the payment of principal of, any premium or interest on, or any additional amounts with respect to, the Comerica debt securities or to enforce any of the covenants of the Comerica debt securities or the applicable Comerica indenture.

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Exercise of Debt Warrants

You may exercise your debt warrants by surrendering at the office of the debt warrant agent your debt warrant certificate with the form of election to purchase on the reverse side of the certificate properly completed and signed by you, which signature must be guaranteed by a bank or trust company, by a broker or dealer which is a member of FINRA or by a member of a national securities exchange. You must also submit a payment in full of the exercise price, as set forth in the applicable prospectus supplement. Upon the exercise of debt warrants, Comerica will issue the debt securities in authorized denominations in accordance with your instructions. If you exercise less than all of the debt warrants evidenced by your debt warrant certificate, a new debt warrant certificate will be issued for the remaining number of debt warrants.

DESCRIPTION OF STOCK PURCHASE CONTRACTS AND STOCK PURCHASE UNITS

Comerica may issue stock purchase contracts, including contracts obligating holders to purchase from or sell to Comerica, and Comerica to sell to or purchase from the holders, a specified number of shares of common stock, shares of preferred stock or depositary shares at a future date or dates. The consideration per share of common stock, preferred stock or depositary shares and the number of shares of each may be fixed at the time the stock purchase contracts are issued or may be determined by reference to a specific formula set forth in the stock purchase contracts. The stock purchase contracts may be issued separately or as part of units, often known as stock purchase units, consisting of a stock purchase contract and any combination of:

• debt securities;

• debt obligations of third parties, including U.S. Treasury securities; or

• other securities identified in the applicable prospectus supplement,

which may secure the holders’ obligations to purchase the common stock, preferred stock or depositary shares under the stock purchase contracts. The stock purchase contracts may require Comerica to make periodic payments to the holders of the stock purchase units or vice versa, and these payments may be unsecured or prefunded on some basis. The stock purchase contracts may require holders to secure their obligations under those contracts in a specified manner.

The applicable prospectus supplement will describe the terms of the stock purchase contracts and stock purchase units, including, if applicable, collateral or depositary arrangements.

PLAN OF DISTRIBUTION

Comerica may offer the offered securities in one or more of the following ways from time to time:

• to or through underwriters or dealers;

• by itself directly;

• through agents; or

• through a combination of any of these methods of sale.

Any such underwriters, dealers or agents may include any broker-dealer subsidiary of Comerica.

The prospectus supplement relating to an offering of offered securities will set forth the terms of such offering, including:

• the name or names of any underwriters, dealers or agents;

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• the purchase price of the offered securities and the proceeds to Comerica from such sale;

• any underwriting discounts and commissions or agency fees and other items constituting underwriters’ or agents’ compensation;

• the initial public offering price;

• any discounts or concessions to be allowed or reallowed or paid to dealers; and

• any securities exchanges on which such offered securities may be listed.

Any initial public offering prices, discounts or concessions allowed or reallowed or paid to dealers may be changed from time to time.

If underwriters are used in an offering of offered securities, such offered securities will be acquired by the underwriters for their own account and may be resold from time to time in one or more transactions, including negotiated transactions, at a fixed public offering price or at varying prices determined at the time of sale. The securities may be offered either to the public through underwriting syndicates represented by one or more managing underwriters or by one or more underwriters without a syndicate. Unless otherwise specified in connection with a particular offering of securities, the underwriters will not be obligated to purchase offered securities unless specified conditions are satisfied, and if the underwriters do purchase any offered securities, they will purchase all offered securities.

In connection with underwritten offerings of the offered securities and in accordance with applicable law and industry practice, underwriters may over-allot or effect transactions that stabilize, maintain or otherwise affect the market price of the offered securities at levels above those that might otherwise prevail in the open market, including by entering stabilizing bids, effecting syndicate covering transactions or imposing penalty bids, each of which is described below.

• A stabilizing bid means the placing of any bid, or the effecting of any purchase, for the purpose of pegging, fixing or maintaining the price of a security.

• A syndicate covering transaction means the placing of any bid on behalf of the underwriting syndicate or the effecting of any purchase to reduce a short position created in connection with the offering.

• A penalty bid means an arrangement that permits the managing underwriter to reclaim a selling concession from a syndicate member in connection with the offering when offered securities originally sold by the syndicate member are purchased in syndicate covering transactions.

These transactions may be effected on the NYSE, in theover-the-counter market, or otherwise. Underwriters are not required to engage in any of these activities, or to continue such activities if commenced.

If dealers are utilized in the sale of offered securities, Comerica will sell such offered securities to the dealers as principals. The dealers may then resell such offered securities to the public at varying prices to be determined by such dealers at the time of resale. The names of the dealers and the terms of the transaction will be set forth in the prospectus supplement relating to that transaction.

Offered securities may be sold directly by Comerica to one or more institutional purchasers, or through agents designated by Comerica from time to time, at a fixed price or prices, which may be changed, or at varying prices determined at the time of sale. Any agent involved in the offer or sale of the offered securities in respect of which this prospectus is delivered will be named, and any commissions payable by Comerica to such agent will be set forth, in the prospectus supplement relating to that offering. Unless otherwise specified in connection with a particular offering of securities, any such agent will be acting on a best efforts basis for the period of its appointment.

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As one of the means of direct issuance of offered securities, Comerica may utilize the services of an entity through which it may conduct an electronic “dutch auction” or similar offering of the offered securities among potential purchasers who are eligible to participate in the auction or offering of such offered securities, if so described in the applicable prospectus supplement.

If so indicated in the applicable prospectus supplement, Comerica will authorize agents, underwriters or dealers to solicit offers from certain types of institutions to purchase offered securities from Comerica at the public offering price set forth in such prospectus supplement pursuant to delayed delivery contracts providing for payment and delivery on a specified date in the future. Such contracts will be subject only to those conditions set forth in the prospectus supplement and the prospectus supplement will set forth the commission payable for solicitation of such contracts.

Comerica Securities, Inc., Comerica’s broker-dealer subsidiary, is a member of FINRA, and may participate in distributions of the offered securities. Accordingly, offerings of offered securities in which Comerica Securities, Inc. participates will conform with the requirements of FINRA’s conflict of interest rules.

This prospectus, together with any applicable prospectus supplement, may also be used by any broker-dealer subsidiary of Comerica in connection with offers and sales of the offered securities in market-making transactions, including block positioning and block trades, at negotiated prices related to prevailing market prices at the time of sale. Any of Comerica’s broker-dealer subsidiaries may act as principal or agent in such transactions. None of Comerica’s broker-dealer subsidiaries have any obligation to make a market in any of the offered securities and may discontinue any market-making activities at any time without notice, at its sole discretion.

One or more dealers, referred to as “remarketing firms,” may also offer or sell the securities, if the prospectus supplement so indicates, in connection with a remarketing arrangement contemplated by the terms of the securities. Remarketing firms will act as principals for their own accounts or as agents. The prospectus supplement will identify any remarketing firm and the terms of its agreement, if any, with Comerica and will describe the remarketing firm’s compensation. Remarketing firms may be deemed to be underwriters in connection with the remarketing of the securities.

Underwriters, dealers and agents may be entitled, under agreements with Comerica, to indemnification by Comerica relating to material misstatements and omissions. Underwriters, dealers and agents may be customers of, engage in transactions with, or perform services for, Comerica and affiliates of Comerica in the ordinary course of business.

Except for securities issued upon a reopening of a previous series, each series of offered securities will be a new issue of securities and will have no established trading market. Any underwriters to whom offered securities are sold for public offering and sale may make a market in such offered securities, but such underwriters will not be obligated to do so and may discontinue any market making at any time without notice. The offered securities may or may not be listed on a securities exchange. No assurance can be given that there will be a market for the offered securities.

ERISA CONSIDERATIONS

A fiduciary of a pension, profit-sharing or other employee benefit plan governed by the Employee Retirement Income Security Act of 1974, as amended (“ERISA”), should consider the fiduciary standards of ERISA in the context of the ERISA plan’s particular circumstances before authorizing an investment in the offered securities of Comerica. Among other factors, the fiduciary should consider whether such an investment is in accordance with the documents governing the ERISA plan and whether the investment is appropriate for the ERISA plan in view of its overall investment policy and diversification of its portfolio.

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Certain provisions of ERISA and the Internal Revenue Code of 1986, as amended (the “Code”), prohibit employee benefit plans (as defined in Section 3(3) of ERISA) that are subject to Title I of ERISA, plans described in Section 4975(e)(1) of the Code (including, without limitation, individual retirement accounts and Keogh Plans) that are subject to Section 4975 of the Code, and entities whose assets include plan assets by reason of a plan’s investment in such entities (including, without limitation, as applicable, insurance company general accounts), from engaging in certain transactions involving “plan assets” with parties that are “parties in interest” under ERISA or “disqualified persons” under the Code with respect to the plan or entity. Governmental and other plans that are not subject to ERISA or to the Code may be subject to similar restrictions undernon-U.S., state, federal or local law. Any employee benefit plan or other entity, to which such provisions of ERISA, the Code or similar law apply, proposing to acquire the offered securities should consult with its legal counsel.

Comerica has subsidiaries, including insurance company subsidiaries and broker-dealer subsidiaries, that provide services to many employee benefit plans. Comerica and any such direct or indirect subsidiary of Comerica may each be considered a “party in interest” and a “disqualified person” to a large number of plans. The acquisition of offered securities of Comerica by any such plan would be likely to result in a prohibited transaction between the plan and Comerica.

Accordingly, unless otherwise provided in connection with a particular offering of securities, offered securities may not be acquired, held or disposed of by any plan or any other person investing “plan assets” of any plan that is subject to the prohibited transaction rules of ERISA or Section 4975 of the Code or other similar law, unless one of the following Prohibited Transaction Class Exemptions (“PTCE”) or a similar exemption or exception applies to such acquisition, holding and disposition:

• PTCE96-23 for transactions determined byin-house asset managers,

• PTCE95-60 for transactions involving insurance company general accounts,

• PTCE91-38 for transactions involving bank collective investment funds,

• PTCE90-1 for transactions involving insurance company separate accounts,

• PTCE84-14 for transactions determined by independent qualified professional asset managers, or

• Section 408(b)(17) of ERISA or Section 4975(d)(20) of the Code for transactions with certain service providers (the “Service Provider Exemption”).

Unless otherwise provided in connection with a particular offering of securities, any purchaser or transferee of the offered securities or any interest therein will be deemed to have represented and warranted to Comerica on each day including the date of its acquisition of the offered securities through and including the date of disposition of such offered securities that either:

(a) it is not a plan subject to Title I of ERISA or Section 4975 of the Code and is not acquiring such securities or interest therein on behalf of, or with “plan assets” of, any such plan;

(b) its acquisition, holding and disposition of such securities are not and will not be prohibited because they are exempted by one or more of the following prohibited transaction exemptions: PTCE96-23,95-60,91-38,90-1,84-14 or the Service Provider Exemption; or

(c) it is a governmental plan (as defined in section 3(32) of ERISA) or other plan that is not subject to the provisions of Title I of ERISA or Section 4975 of the Code and its acquisition, holding and disposition of such securities are not otherwise prohibited.

Due to the complexity of these rules and the penalties imposed upon persons involved in prohibited transactions, it is important that any person considering the acquisition of the offered securities with plan assets consult with its counsel regarding the consequences under ERISA and the Code, or other similar law, of the acquisition and ownership of offered securities and the availability of exemptive relief under the class exemptions listed above.

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The sale of any securities to any plan is in no respect a representation by Comerica or any of its affiliates or representatives that such an investment is appropriate for or meets all relevant legal requirements with respect to investments by plans generally or any particular plan. Please consult the applicable prospectus supplement for further information with respect to a particular offering and, in certain cases, further restrictions on the purchase or transfer of securities.

LEGAL MATTERS

The validity of these securities has been passed upon for Comerica by Mayer Brown LLP, Chicago, Illinois. In connection with particular offerings of the securities in the future, the validity of the securities may be passed upon for Comerica by one of Comerica’s lawyers or other counsel to Comerica named in the applicable prospectus supplement and for underwriters, agents or dealers by Mayer Brown LLP, Chicago, Illinois. From time to time, Mayer Brown LLP has represented Comerica on various matters and may do so in the future.

EXPERTS

The consolidated financial statements of Comerica Incorporated incorporated by reference in Comerica Incorporated’s Annual Report (Form10-K) for the year ended December 31, 2017, and the effectiveness of Comerica Incorporated’s internal control over financial reporting as of December 31, 2017 have been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their reports thereon, incorporated by reference therein, and incorporated herein by reference. Such consolidated financial statements are incorporated herein by reference in reliance upon such reports given on the authority of such firm as experts in accounting and auditing.

WHERE YOU CAN FIND MORE INFORMATION

Comerica files annual, quarterly and special reports, proxy statements and other information with the SEC. You may read and copy any document Comerica files in the SEC’s Public Reference Room, 100 F Street, N.E., Washington, D.C. 20549. You may also obtain copies of this information by mail from the Public Reference Section of the SEC, 100 F Street, N.E., Washington, D.C. 20549, at prescribed rates. You may obtain information on the operation of the SEC’s Public Reference Room in Washington, D.C. by calling the SEC at1-800-SEC-0330. The SEC also maintains an Internet web site that contains reports, proxy and information statements and other information about issuers, like us, that file electronically with the SEC. The address of that site is http://www.sec.gov. The SEC file number for documents Comerica files under the Exchange Act is001-10706. The reports and other information Comerica files with the SEC also are available at Comerica’s website, www.comerica.com. We have included the SEC’s web address and our web address as inactive textual references only. Except as specifically incorporated by reference into this prospectus, information on those websites is not part of this prospectus.

Comerica is allowed to “incorporate by reference” the information Comerica files with the SEC, which means that it can disclose important information to you by referring you to those documents. The information incorporated by reference is an important part of this prospectus, and information that Comerica files subsequently with the SEC will automatically update and supersede the information included and/or incorporated by reference in this prospectus. Comerica incorporates by reference the documents listed below and any future filings made with the SEC (other than portions of these documents that are furnished under Item 2.02 or Item 7.01 of a Current Report on Form8-K, including any exhibits included with such Items, or other information deemed to have been “furnished” rather than filed in accordance with the SEC’s rules) under Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended, after the initial filing of

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the Registration Statement that contains this prospectus and prior to the time that Comerica sells all of the securities offered by this prospectus:

• Annual Report on Form10-K for the year ended December 31, 2017;

• Current Reports on Form8-K filed on January 24, 2018 and February 8, 2018; and

• The description of Comerica’s common stock contained in the Registration Statement on FormS-4/A filed on April 5, 2011 (Commission File Number333-172211).

Upon written or oral request, we will provide — at no cost to the requester — a copy of any or all of the information that has been incorporated by reference in this prospectus but not delivered with this prospectus (other than exhibits, unless that exhibit is specifically incorporated by reference into that filing). You may make a request by writing to the following address or calling the following telephone number:

Investor Relations

Comerica Incorporated

Comerica Bank Tower

1717 Main Street

Dallas, Texas 75201

Telephone number:(214) 462-6831

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$                

Comerica Incorporated

$        Floating Rate Senior Notes due

$        % Senior Notes due

Joint Book-Running Managers

J.P. Morgan Morgan Stanley   RBC Capital Markets

Co-Manager

Comerica Securities