Fortis SUPPL Supplemental materials

Use these links to rapidly review the document
TABLE OF CONTENTS
Table of Contents

Filed pursuant to General
Instruction II.L. of Form F-10
File No. 333-214787

PROSPECTUS SUPPLEMENT
(to Prospectus dated November 30, 2016)

FORTIS INC.

$500,000,000

COMMON SHARES

This prospectus supplement, or the Prospectus Supplement, together with the short form base shelf prospectus to which it relates dated November 30, 2016, as amended or supplemented, or the Prospectus, qualifies the distribution, or the Offering, of common shares of Fortis Inc., or the Common Shares, having an aggregate sale price of up to $500,000,000 (or the equivalent in U.S. dollars determined using the daily exchange rate posted by the Bank of Canada on the date the Common Shares are sold). See "Plan of Distribution".

Our issued and outstanding Common Shares are listed on the Toronto Stock Exchange, or TSX, and the New York Stock Exchange, or the NYSE, under the symbol "FTS". On March 23, 2018, the closing prices of the Common Shares on such exchanges were $43.25 and US$33.57, respectively. We have applied to list the Common Shares offered by this Prospectus Supplement for trading on the TSX and the NYSE. The listing of such Common Shares on the TSX and the NYSE will be subject to our fulfillment of all of the listing requirements of the TSX and NYSE, respectively.

We have entered into an equity distribution agreement dated March 26, 2018, or the Distribution Agreement, with Scotia Capital Inc., TD Securities Inc., Morgan Stanley Canada Limited and Wells Fargo Securities Canada Ltd., or collectively, the Canadian Agents, and Scotia Capital (USA) Inc., TD Securities (USA) LLC, Morgan Stanley & Co. LLC and Wells Fargo Securities, LLC, or collectively, the U.S. Agents, and together with the Canadian Agents, the Agents, pursuant to which we may distribute Common Shares in the Offering from time to time through the Agents, as agents, in accordance with the terms of the Distribution Agreement. Sales of Common Shares, if any, under this Prospectus Supplement and the accompanying Prospectus are anticipated to be made in transactions that are deemed to be "at-the-market distributions" as defined in National Instrument 44-102 — Shelf Distributions, or NI 44-102, including sales made directly on the TSX or the NYSE or on any other trading market for the Common Shares in Canada or the United States, or the U.S. The Common Shares will be distributed at the market prices prevailing at the time of the sale. As a result, prices at which Common Shares are sold may vary as between purchasers and during the period of any distribution.There is no minimum amount of funds that must be raised under the Offering. This means that the Offering may terminate after raising only a portion of the offering amount set out above, or none at all. See "Plan of Distribution".

We will pay the Agents compensation for their services in acting as agents in connection with the sale of Common Shares pursuant to the Distribution Agreement of up to 2% of the gross sales price per Common Share sold, or the Commission, which amount will be paid in the same currency as the Common Shares to which such Commission pertains were sold.

Investing in the Common Shares involves certain risks that should be carefully considered. See the "Risk Factors" section of the Prospectus, as well as "Risks Related to the Common Shares" in this Prospectus Supplement.

We are permitted, under the multi-jurisdictional disclosure system adopted by the U.S. and Canada, to prepare this Prospectus Supplement in accordance with Canadian disclosure requirements. You should be aware that such requirements are different from U.S. disclosure requirements. Financial statements incorporated by reference herein have been prepared in accordance with U.S. generally accepted accounting principles, or U.S. GAAP.

The acquisition of the securities described herein may subject you to tax consequences in both the U.S. and Canada. This Prospectus Supplement and the accompanying Prospectus may not describe these tax consequences fully. See "Certain Canadian Federal Income Tax Considerations" and "Certain U.S. Federal Income Tax Considerations".

Your ability to enforce civil liabilities under U.S. federal securities laws may be affected adversely because we are incorporated under the laws of the Province of Newfoundland and Labrador, Canada, some of our officers and directors and some of the experts named in this Prospectus Supplement and the Prospectus are non-U.S. residents, and some of our assets and some of the assets of those officers, directors and experts are located outside of the U.S. See "Enforceability of Civil Liabilities".

THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE U.S. SECURITIES AND EXCHANGE COMMISSION, OR THE SEC, NOR HAS THE SEC PASSED UPON THE ADEQUACY OR ACCURACY OF THIS PROSPECTUS SUPPLEMENT OR THE PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.


Scotiabank		TD Securities		Morgan Stanley		Wells Fargo Securities

The date of this prospectus supplement is March 26, 2018

As sales agents, the Agents will not engage in any transactions to stabilize or maintain the price of the Common Shares. No underwriter or dealer involved in the distribution, no affiliate of such an underwriter or dealer and no person or company acting jointly or in concert with such an underwriter or dealer has over-allotted, or will over-allot, Common Shares in connection with the Offering or has effected, or will effect, any other transactions that are intended to stabilize or maintain the market price of the Common Shares.

Each of the Agents is an affiliate of a financial institution that has, either solely or as a member of a syndicate of financial institutions, extended credit facilities to, or holds other indebtedness of, us and/or our subsidiaries. Consequently, we may be considered a "connected issuer" of the Agents within the meaning of applicable securities legislation. The net proceeds from this Offering may be used to reduce our indebtedness to such lenders. See "Relationship with Certain of the Agents", "Use of Proceeds" and "Plan of Distribution".

The Canadian Agents will only sell Common Shares on marketplaces in Canada and the U.S. Agents will only sell Common Shares on marketplaces in the U.S.

Table of Contents

TABLE OF CONTENTS

Prospectus Supplement

		Page

NOTICE TO READERS			S-2
SPECIAL NOTE REGARDING FORWARD-LOOKING INFORMATION			S-2
DOCUMENTS INCORPORATED BY REFERENCE			S-4
WHERE YOU CAN FIND ADDITIONAL INFORMATION			S-5
PRESENTATION OF FINANCIAL INFORMATION			S-5
CURRENCY AND EXCHANGE RATE INFORMATION			S-6
FORTIS			S-6
RISKS RELATED TO THE COMMON SHARES			S-6
CONSOLIDATED CAPITALIZATION			S-7
DESCRIPTION OF THE COMMON SHARES			S-8
DIVIDEND POLICY			S-8
USE OF PROCEEDS			S-8
PLAN OF DISTRIBUTION (CONFLICTS OF INTEREST)			S-8
RELATIONSHIP WITH CERTAIN OF THE AGENTS			S-10
PRIOR SALES			S-11
TRADING PRICES AND VOLUMES			S-12
CERTAIN CANADIAN FEDERAL INCOME TAX CONSIDERATIONS			S-12
CERTAIN U.S. FEDERAL INCOME TAX CONSIDERATIONS			S-15
LEGAL MATTERS			S-18
EXPERTS			S-18
ENFORCEABILITY OF CIVIL LIABILITIES			S-18
AUDITOR			S-19
DOCUMENTS FILED AS PART OF THE REGISTRATION STATEMENT			S-19

Prospectus

		Page

NOTICE TO READERS			2
SPECIAL NOTE REGARDING FORWARD- LOOKING STATEMENTS			2
DOCUMENTS FILED AS PART OF THE REGISTRATION STATEMENT			4
DOCUMENTS INCORPORATED BY REFERENCE			4
WHERE YOU CAN FIND ADDITIONAL INFORMATION			6
PRESENTATION OF FINANCIAL INFORMATION			6
CURRENCY AND EXCHANGE RATE INFORMATION			7
FORTIS			7
SHARE CAPITAL OF FORTIS			8
EARNINGS COVERAGE RATIOS			8
DIVIDEND POLICY			9
DESCRIPTION OF SECURITIES OFFERED			10
CHANGES IN SHARE AND LOAN CAPITAL STRUCTURE			16
PRIOR SALES			17
TRADING PRICES AND VOLUMES			18
USE OF PROCEEDS			20
PLAN OF DISTRIBUTION			20
SELLING SECURITYHOLDERS			21
CERTAIN INCOME TAX CONSIDERATIONS			22
RISK FACTORS			22
AUDITORS			24
LEGAL MATTERS			24
ENFORCEABILITY OF CIVIL LIABILITIES			24
GLOSSARY			25

Table of Contents

NOTICE TO READERS

This document is in two parts. The first part is this Prospectus Supplement, which describes the specific terms of the Offering and also adds to and updates certain information contained in the Prospectus and the documents incorporated by reference herein and therein. The second part is the Prospectus, which gives more general information, some of which may not apply to the Offering. This Prospectus Supplement is deemed to be incorporated by reference in the Prospectus solely for the purpose of the Offering.

If the description of the Common Shares varies between this Prospectus Supplement and the Prospectus, you should rely on the information in this Prospectus Supplement.

You should rely only on the information contained in or incorporated by reference in this Prospectus Supplement and the Prospectus. We have not authorized anyone to provide you with different or additional information. We are not making an offer of Common Shares in any jurisdiction where the offer is not permitted by law. The information contained in this Prospectus Supplement, the Prospectus and the documents incorporated by reference herein and therein is accurate only as of the respective dates of those documents, and you should not assume otherwise.

Unless we have indicated otherwise, or the context otherwise requires, references in this Prospectus Supplement to "Fortis", "we", "us" and "our" refer to Fortis Inc. and its consolidated subsidiaries.

SPECIAL NOTE REGARDING FORWARD-LOOKING INFORMATION

This Prospectus Supplement and the Prospectus, including the documents incorporated herein and therein by reference, contain "forward-looking information" within the meaning of applicable Canadian securities laws and "forward-looking statements" within the meaning of the U.S. Private Securities Litigation Reform Act of 1995, collectively referred to herein as "forward-looking information". The forward-looking information reflects our current expectations regarding our future growth, results of operations, performance, business prospects and opportunities, based on information currently available. These expectations may not be appropriate for other purposes. All forward-looking information is given pursuant to the "safe harbour" provisions of applicable Canadian securities legislation. The words "anticipates", "assumes", "believes", "budgets", "can", "could", "estimates", "expects", "forecasts", "intends", "may", "might", "opportunity", "plans", "projects", "seeks", "schedule", "should", "target", "will", "would" and the negative of these terms and similar expressions are often intended to identify forward-looking information, although not all forward-looking information contains these identifying words. The forward-looking information reflects management's current beliefs and is based on information currently available to us.

The forward-looking information in this Prospectus Supplement and the Prospectus, including the documents incorporated herein and therein by reference, includes, but is not limited to, statements regarding: the aggregate amount of the total proceeds that we will receive pursuant to the Offering; the expectation that we will not be a "passive foreign investment company" for the taxable year ending December 31, 2018 or thereafter; the expectation that we will remain at the forefront of emerging technologies; our forecast gross consolidated and segmented capital expenditures for 2018 and for the period 2018 through 2022 and expected associated increase to rate base; expected consolidated fixed-term debt maturities and repayments in 2018 and over the next five years; the expectation that we and our subsidiaries will continue to have reasonable access to long-term capital in 2018; targeted average annual dividend growth through 2022; expected timing of filing of regulatory applications and receipt and outcome of regulatory decisions; statements related to Fortis Turks and Caicos recovery of lost revenue as a result of the impact of Hurricane Irma and the timing thereof; the nature, timing, funding sources and expected costs of certain capital projects including, without limitation, the ITC Holdings Corp., or ITC, Multi-Value Regional Transmission Projects and 34.6 to 69 kilovolts Conversion Project, UNS Energy Corporation flexible generation resource investment and Gila River Generating Station Unit 2, FortisBC Energy Inc. expansion of the Tilbury liquefied natural gas, or LNG, facility, Eagle Mountain Woodfibre Gas Pipeline Project, Lower Mainland System Upgrade and Pipeline Integrity Management Program and additional opportunities beyond the base plan including the Wataynikaneyap Project, the Lake Erie Connector Project and additional LNG infrastructure investment in British Columbia; the expectation that subsidiary operating expenses and interest costs will be paid out of subsidiary operating cash flows; the expectation that cash required to complete subsidiary capital expenditure programs will be sourced from a combination of borrowings under

S-2

Table of Contents

credit facilities, long-term debt offerings and equity injections from us; the expectation that maintaining the targeted capital structure of our regulated operating subsidiaries will not have an impact on our ability to pay dividends in the foreseeable future; the expectation that cash required by us to support subsidiary capital expenditure programs and finance acquisitions will be derived from a combination of borrowings under our committed corporate credit facility and proceeds from the issuance of common shares, preference shares and long-term debt; the expectation that we and our subsidiaries will remain compliant with debt covenants throughout 2018; statements related to the Offering, including the expected use of proceeds from the Offering, if any; the intent of management to refinance certain borrowings under our long-term committed credit facilities with long-term permanent financing; the expectation that the adoption of future accounting pronouncements will not have a material impact on our consolidated financial statements; the impact of U.S. tax reform on our annual earnings per share and cash flow at our U.S. regulated utilities; and the expectation that long-term sustainable growth in rate base will support continuing growth in earnings and dividends.

The forecasts and projections that make up the forward-looking information included in this Prospectus Supplement and the Prospectus are based on assumptions which include, but are not limited to: the receipt of applicable regulatory approvals and requested rate orders, no material adverse regulatory decisions being received, and the expectation of regulatory stability; no material capital project and financing cost overrun related to any of our capital projects; the realization of additional opportunities; our board of directors, or the Board of Directors, exercising its discretion to declare dividends, taking into account our business performance and financial condition; no significant variability in interest rates; no significant operational disruptions or environmental liability due to a catastrophic event or environmental upset caused by severe weather, other acts of nature or other major events; the continued ability to maintain our electricity and gas systems to ensure their continued performance; no severe and prolonged downturn in economic conditions; no significant decline in capital spending; sufficient liquidity and capital resources; the continuation of regulator-approved mechanisms to flow through the cost of natural gas and energy supply costs in customer rates; the ability to hedge exposures to fluctuations in foreign exchange rates, natural gas prices and electricity prices; no significant changes in tax laws; no significant counterparty defaults; the continued competitiveness of natural gas pricing when compared with electricity and other alternative sources of energy; the continued availability of natural gas, fuel, coal and electricity supply; continuation and regulatory approval of power supply and capacity purchase contracts; the ability to fund defined benefit pension plans, earn the assumed long-term rates of return on the related assets and recover net pension costs in customer rates; no significant changes in government energy plans, environmental laws and regulations that may materially negatively affect us or our subsidiaries; maintenance of adequate insurance coverage; the ability to obtain and maintain licences and permits; retention of existing service areas; the continued tax deferred treatment of earnings from our foreign operations; continued maintenance of information technology infrastructure and no material breach of cyber-security; continued favourable relations with First Nations; favourable labour relations; that we can reasonably assess the merit of and potential liability attributable to ongoing legal proceedings; and sufficient human resources to deliver service and execute the capital program.

The forward-looking information involves significant risks, uncertainties and other factors that could cause actual results to differ materially from historical results or results anticipated by the forward-looking information. Factors which could cause results or events to differ from current expectations include, but are not limited to: the price at which Common Shares are sold in the Offering and the aggregate net proceeds received by us as a result of the Offering; uncertainty regarding the outcome of regulatory proceedings at our utilities; uncertainty of the impact a continuation of a low interest rate environment may have on the allowed rate of return on common shareholders' equity at our regulated utilities; the impact of fluctuations in foreign exchange rates; uncertainty related to the impact of the U.S. Tax Cuts and Jobs Act on our future results of operations; risk associated with the impacts of less favourable economic conditions on our results of operations; risk associated with our ability to continue to comply with Section 404(a) of theSarbanes-Oxley Act of 2002 and the related rules of the SEC and the Public Company Accounting Oversight Board; risk associated with the completion of our 2018 capital expenditure program, including completion of major capital projects on the timelines anticipated and at the expected amounts; and uncertainty in the timing and access to capital markets to arrange sufficient and cost-effective financing to finance, among other things, capital expenditures and the repayment of maturing debt. For additional information with respect to our risk factors and risk factors relating to the Common Shares, reference should be made to the section of this Prospectus Supplement entitled "Risks

S-3

Table of Contents

Related to the Common Shares", the section of the Prospectus entitled "Risk Factors", to the documents incorporated herein and therein by reference and to our continuous disclosure materials filed from time to time with Canadian securities regulatory authorities and with the SEC.

All forward-looking information in this Prospectus Supplement, the Prospectus and in the documents incorporated herein and therein by reference is qualified in its entirety by the above cautionary statements and we disclaim any intention or obligation to update or revise any forward-looking information, whether as a result of new information, future events or otherwise.

DOCUMENTS INCORPORATED BY REFERENCE

This Prospectus Supplement is deemed to be incorporated by reference in the Prospectus solely for the purpose of the Offering. The following documents filed by us with the securities commission or similar authority in each of the provinces of Canada are specifically incorporated by reference in, and form an integral part of, this Prospectus Supplement and the Prospectus:

(a): our Annual Information Form dated February 14, 2018, for the fiscal year ended December 31, 2017;
(b): our audited consolidated financial statements as at December 31, 2017 and December 31, 2016 and for the fiscal years then ended, together with the notes thereto, or the Annual Financial Statements, and the auditor report thereon of Deloitte LLP dated February 14, 2018 and the auditor report thereon of Ernst & Young LLP, our former auditor, dated February 15, 2017, except as to Note 31 which is dated as of February 14, 2018;
(c): our Management Discussion and Analysis of financial condition and results of operations dated February 14, 2018 for the fiscal year ended December 31, 2017, or the Annual MD&A; and
(d): our Management Information Circular dated March 17, 2017 prepared in connection with our annual and special meeting of shareholders held on May 4, 2017.

Any document of the type referred to above, including any material change report (other than any confidential material change report), any business acquisition report and any prospectus supplements relating to the Offering disclosing additional or updated information, subsequently filed by us with such securities commissions or regulatory authorities in Canada after the date of this Prospectus Supplement, and prior to the termination of the Offering, shall be deemed to be incorporated by reference into this Prospectus Supplement and the Prospectus. In addition, pursuant to the decision dated March 23, 2018 granted by the Ontario Securities Commission, or the OSC, (as principal regulator) pursuant to National Policy 11-203 — Process for Exemptive Relief Applications in Multiple Jurisdictions, or the Decision, if we disseminate a news release in respect of previously undisclosed information that, in our determination, constitutes a "material fact" (as such term is defined under applicable Canadian securities laws), we will identify such news release as a "designated news release" for the purposes of this Prospectus Supplement and the Prospectus in writing on the face page of the version of such news release that we file on the Canadian Securities Administrator's System for Electronic Document Analysis and Retrieval, or SEDAR, each such news release a Designated News Release, and each such Designated News Release shall be deemed to be incorporated by reference into this Prospectus Supplement and the Prospectus only for the purposes of the Offering.

Documents and information in an annual report on Form 40-F filed by us with the SEC under the U.S. Securities Exchange Act of 1934, as amended, or the Exchange Act, from the date of this Prospectus Supplement and prior to the termination or completion of the Offering shall be deemed to be incorporated by reference into this Prospectus Supplement and the registration statement of which this Prospectus Supplement forms a part. In addition, any other report on Form 6-K and the exhibits thereto filed or furnished by us with the SEC under the Exchange Act from the date of this Prospectus Supplement and prior to the termination or completion of the Offering shall be deemed to be incorporated by reference into this Prospectus Supplement or as exhibits to the registration statement of which this Prospectus Supplement forms a part, as applicable, but only if and to the extent expressly so provided in such reports. Our current reports on Form 6-K and our annual reports on Form 40-F are available on the SEC's Electronic Data Gathering and Retrieval website, or EDGAR, at www.sec.gov.

S-4

Table of Contents

Any statement contained in this Prospectus Supplement, the Prospectus or in a document incorporated or deemed to be incorporated by reference in this Prospectus Supplement or the Prospectus shall be deemed to be modified or superseded for the purposes of this Prospectus Supplement and the Prospectus to the extent that a statement contained in this Prospectus Supplement, or in any subsequently filed document which is or is deemed to be incorporated by reference in this Prospectus Supplement or the Prospectus, modifies or supersedes that statement. The modifying or superseding statement need not state that it has modified or superseded a prior statement or include any other information set forth in the document that it modifies or supersedes. The making of a modifying or superseding statement shall not be deemed an admission for any purposes that the modified or superseded statement, when made, constituted a misrepresentation, an untrue statement of a material fact or an omission to state a material fact that is required to be stated or that is necessary to make a statement not misleading in light of the circumstances in which it was made. Any statement so modified or superseded shall not constitute a part of this Prospectus Supplement or the Prospectus except as so modified or superseded.

WHERE YOU CAN FIND ADDITIONAL INFORMATION

Copies of the documents incorporated in this Prospectus Supplement and the Prospectus by reference may be obtained on request without charge from our Corporate Secretary at Suite 1100, 5 Springdale Street, P.O. Box 8837, St. John's, Newfoundland and Labrador, A1B 3T2 (telephone (709) 737-2800). These documents are also available through the Internet on our website atwww.fortisinc.com or on SEDAR which can be accessed atwww.sedar.com. The information contained on, or accessible through, any of these websites is not incorporated by reference into this Prospectus Supplement or the Prospectus and is not, and should not be considered to be, a part of this Prospectus Supplement or the Prospectus unless it is explicitly so incorporated.

In addition to our continuous disclosure obligations under the securities laws of the provinces of Canada, we are subject to the informational requirements of the Exchange Act and in accordance therewith file reports and other information with the SEC. Under the multi-jurisdictional disclosure system adopted by the U.S., or MJDS, such reports and other information may be prepared in accordance with the disclosure requirements of Canada, which requirements are different from those of the U.S. Any information filed with the SEC can be read and copied at prescribed rates at the SEC's Public Reference Room at 100 F Street, N.E., Washington, D.C. 20549. Information on the operation of the Public Reference Room may be obtained by calling the SEC at 1-800-SEC-0330 or by accessing its website atwww.sec.gov. Some of the documents that we file with or furnish to the SEC are electronically available from the SEC's Electronic Document Gathering and Retrieval System, which is commonly known by the acronym "EDGAR", and may be accessed at www.sec.gov.

We have filed with the SEC a registration statement on Form F-10 (File No. 333-214787) under the U.S. Securities Act of 1933, as amended, or the Securities Act, with respect to the Common Shares offered by this Prospectus Supplement. This Prospectus Supplement, which forms a part of the registration statement, does not contain all of the information set forth in the registration statement, certain parts of which have been omitted in accordance with the rules and regulations of the SEC. For further information with respect to us and the Offering, reference is made to the registration statement and to the schedules and exhibits filed therewith. Statements contained in this Prospectus Supplement as to the contents of certain documents are not necessarily complete and, in each instance, reference is made to the copy of the document filed as an exhibit to the registration statement. Each such statement is qualified in its entirety by such reference.

PRESENTATION OF FINANCIAL INFORMATION

Financial statements incorporated by reference in this Prospectus Supplement and the Prospectus have been prepared in accordance with U.S. GAAP. Certain calculations included in tables and other figures in this Prospectus Supplement and the Prospectus have been rounded for clarity of presentation.

S-5

Table of Contents

CURRENCY AND EXCHANGE RATE INFORMATION

This Prospectus Supplement contains references to U.S. dollars and Canadian dollars. All dollar amounts referenced, unless otherwise indicated, are expressed in Canadian dollars. References to "$" or "C$" are to Canadian dollars and references to "US$" are to U.S. dollars. The following table shows, for the years indicated, certain information regarding the Canadian dollar/U.S. dollar exchange rate. The information is based on the historical noon exchange rate as reported by the Bank of Canada for all periods prior to March 1, 2017, and on the daily average rate as reported by the Bank of Canada for all periods on and after March 1, 2017. Such exchange rate on March 23, 2018 was C$1.2856 = US$1.00.

		Average⁽¹⁾

		(C$ per US$)
Year ended December 31,
2017	1.2545		1.2986	1.2128	1.3743
2016	1.3427		1.3248	1.2544	1.4589

(1): The average of the noon buying rates and daily average rates, as applicable, during the relevant period.

FORTIS

We are principally an international electric and gas utility holding company, with total assets of approximately $48 billion as at December 31, 2017 and revenue totaling approximately $8.3 billion for the year ended December 31, 2017. Our electricity systems met a combined peak demand of 32,134 megawatts, or MW, in 2017 and our gas distribution systems met a peak day demand of 1,585 terajoules, or TJ, in 2017. Our approximately 8,500 employees serve utility customers in five Canadian provinces, nine U.S. states and three Caribbean countries.

RISKS RELATED TO THE COMMON SHARES

An investment in the Common Shares offered hereby involves certain risks. You should carefully consider the risk factors described under the heading "Business Risk Management" found on pages 36 to 47 of the Annual MD&A which is incorporated by reference herein. In addition, you should carefully consider, in light of your own financial circumstances, the risk factors set out below which relate to the Common Shares, as well as the other information contained in this Prospectus Supplement, the Prospectus, including under the heading "Risk Factors" found on pages 23 to 25, the documents incorporated by reference herein and therein and in all subsequently filed documents incorporated by reference, before making an investment decision.

Price volatility of Common Shares

The market price of our Common Shares has in the past been, and may in the future be, subject to large fluctuations which may result in losses for investors. The market price of our Common Shares may increase or decrease in response to a number of events and factors, including:

•: our operating performance and the performance of competitors and other similar companies;
•: the public's reaction to our press releases, other public announcements and our filings with the various securities regulatory authorities;
•: changes in earnings estimates or recommendations by research analysts who track our securities;
•: the operating and share price performance of other companies that investors may deem comparable;
•: changes in general economic and/or political conditions;
•: the arrival or departure of key personnel;
•: acquisitions, strategic alliances or joint ventures involving us or our competitors; and
•: the number of Common Shares sold on any one day or in the aggregate pursuant to the Offering.

S-6

Table of Contents

In addition, the market price of our Common Shares is affected by many variables not directly related to our success and not within our control, including other developments that affect the market for all utilities sector securities or the equity markets generally, the breadth of the public market for our Common Shares, and the attractiveness of alternative investments. These variables may adversely affect the prices of our Common Shares regardless of our operating performance.

Uses of the net proceeds from the Offering

We currently expect to apply the net proceeds we receive from the Offering as described under "Use of Proceeds" of this Prospectus Supplement. As described thereunder, management has broad discretion with respect to the actual application of those net proceeds, and may elect to apply such proceeds differently than is described thereunder if management believes that it would be in our best interest to do so. The failure by management to apply the net proceeds effectively could have a material adverse effect on our business.

Future sales or issuances of securities of Fortis

We may issue additional securities to finance future activities outside of the Offering. We cannot predict the size of future issuances of securities or the effect, if any, that future issuances and sales of securities will have on the market price of the Common Shares. Sales or issuances of substantial numbers of Common Shares, or the perception that such sales could occur, may adversely affect prevailing market prices of the Common Shares. In connection with any issuance of Common Shares, investors will suffer dilution to their voting power and we may experience dilution in our earnings per share.

Payment of Future Dividends

Our Board of Directors reviews our financial performance quarterly and makes a determination of the appropriate level of dividends to be declared in the following quarter, if any. Currently, payment of dividends on our Common Shares is funded primarily from dividends we receive from our subsidiaries. Our subsidiaries are separate legal entities and have no independent obligation to pay dividends to us. Prior to paying dividends to us, the subsidiaries have financial obligations that must be satisfied, including, among others, their operating expenses and obligations to creditors. Furthermore, our utilities are required by regulation to maintain a minimum equity-to-total capital ratio that may restrict their ability to pay dividends to us or may require that we contribute capital to them. The future enactment of laws or regulations may prohibit or further restrict the ability of our subsidiaries to pay upstream dividends or to repay intercorporate indebtedness. In addition, in the event of a subsidiary's liquidation or reorganization, our right to participate in a distribution of assets is subject to the prior claims of the subsidiary's creditors. As a result, our ability to generate cash flow to pay dividends is reliant on the ability of our subsidiaries to generate sustained earnings and cash flows and to pay dividends.

CONSOLIDATED CAPITALIZATION

The following describes the changes in our share and loan capital structure from January 1, 2018 to March 23, 2018.

(a): During the period from January 1, 2018 up to and including March 23, 2018, the number of issued and outstanding Common Shares increased by an aggregate of 1,910,381 Common Shares as a result of (i) issuances under our Dividend Reinvestment Plan, or DRIP, and Employee Share Purchase Plan, or ESPP, and (ii) the exercise of options granted pursuant to the 2006 and 2012 Stock Option Plans.
(b): During the period from January 1, 2018 up to and including March 23, 2018, our consolidated long-term debt, capital lease and finance obligations, including current portions and committed credit facility borrowings classified as long-term debt, increased by approximately $574 million, principally due to changes in foreign exchange rates over the period.

We may from time to time during the period that the Offering remains in effect issue and sell Common Shares having an aggregate sale price of up to $500,000,000 (or the equivalent in U.S. dollars determined using the daily exchange rate posted by the Bank of Canada on the date the Common Shares are sold). See "Plan of Distribution".

S-7

Table of Contents

DESCRIPTION OF THE COMMON SHARES

We are authorized to issue an unlimited number of Common Shares. See "Description of Securities Offered — Common Shares" in the Prospectus for a description of the material attributes and characteristics of the Common Shares. As of March 23, 2018, 423,047,800 Common Shares were issued and outstanding.

DIVIDEND POLICY

Dividends on the Common Shares are declared at the discretion of our Board of Directors. We declared and paid cumulative cash dividends on our Common Shares of $1.625 in 2017. On December 7, 2017, our Board of Directors declared a first quarter dividend of $0.425 per Common Share, which was paid on March 1, 2018 to holders of record at the close of business on February 15, 2018. We have increased our annual Common Share dividend payment for 44 consecutive years.

We have targeted average annual dividend growth of approximately 6% through 2022. This dividend guidance takes into account many factors, including the expectation of reasonable outcomes for regulatory proceedings at our utilities, the successful execution of the five-year capital expenditure program, and management's continued confidence in the strength of our diversified portfolio of utilities and record of operational excellence. See "Risks Related to the Common Shares — Payment of Future Dividends".

USE OF PROCEEDS

We intend to use the net proceeds from the Offering, if any, for general corporate purposes. We may invest funds which we do not immediately require in short-term marketable investment grade securities. We may, from time to time, issue securities (including equity securities) other than pursuant to this Prospectus Supplement.

The net proceeds from the Offering are not determinable in light of the nature of the distribution. The net proceeds of any given distribution of Common Shares through the Agents in an "at-the-market distribution" will represent the gross proceeds after deducting the applicable compensation payable to the Agents under the Distribution Agreement and the expenses of the distribution. See "Plan of Distribution".

PLAN OF DISTRIBUTION

We have entered into the Distribution Agreement with the Agents under which we may issue and sell from time to time Common Shares having an aggregate sale price of up to $500,000,000 (or the equivalent in U.S. dollars determined using the daily exchange rate posted by the Bank of Canada on the date the Common Shares are sold) in each of the provinces of Canada and in the U.S. pursuant to placement notices delivered by us to the Agents from time to time in accordance with the terms of the Distribution Agreement. Sales of Common Shares, if any, will be made in transactions that are deemed to be "at-the-market distributions" as defined in NI 44-102, including sales made by the Agents directly on the TSX, the NYSE or any other trading market for the Common Shares in Canada or the U.S. Subject to the pricing parameters in a placement notice, the Common Shares will be distributed at the market prices prevailing at the time of the sale. As a result, price may vary as between purchasers and during the period of distribution. Pursuant to the Decision, the number of Common Shares sold on the TSX or another Canadian marketplace as at-the-market distributions on any trading day will not exceed 25% of the trading volume of the Common Shares on the TSX and all other Canadian marketplaces on that day. We cannot predict the number of Common Shares that we may sell under the Distribution Agreement on the TSX, the NYSE or any other trading market for the Common Shares in Canada or the U.S., or if any Common Shares will be sold.

The Agents will offer the Common Shares subject to the terms and conditions of the Distribution Agreement on a daily basis or as otherwise agreed upon by us and the Agents. We will designate the maximum amount of Common Shares to be sold pursuant to any single placement notice to the applicable Agent or Agents. We will identify in the placement notice which Agent or Agents will effect the placement. Subject to the terms and conditions of the Distribution Agreement, the Agents will use their commercially reasonable efforts to sell, on our behalf, all of the Common Shares requested to be sold by us. We may instruct the Agents not to sell Common Shares if the sales cannot be achieved at or above the price designated by us in a particular placement notice. Under the Distribution Agreement, no Agent has any obligation to purchase as principal for

S-8

Table of Contents

its own account any Common Shares that we propose to sell pursuant to any placement notice delivered by us to the applicable Agent or Agents. If we sell the Common Shares to one or more of the Agents as principal, we will enter into a separate agreement with such Agent or Agents and will describe that agreement in a separate prospectus supplement or free writing prospectus.

Either we or the Agents may suspend the Offering upon proper notice to the other party. We and the Agents each have the right, by giving written notice as specified in the Distribution Agreement, to terminate the Distribution Agreement in each party's sole discretion at any time.

We will pay the Agents the Commission for their services in acting as agents in connection with the sale of Common Shares pursuant to the Distribution Agreement. The amount of the Commission will be up to 2% of the gross sales price per Common Share sold. The Commission will be paid in the same currency as the Common Shares to which such Commission pertains were sold. The sales proceeds remaining after payment of the Commission and after deducting any expenses payable by us and any transaction or filing fees imposed by any governmental, regulatory, or self-regulatory organization in connection with the sales, will equal the net proceeds to us from the sale of such Common Shares.

The applicable Agent or Agents will provide written confirmation to us no later than the opening of the trading day immediately following the trading day on which it has made sales of the Common Shares under the Distribution Agreement. Each confirmation will include the number of Common Shares sold on such day, the average price of the Common Shares sold on such day, the gross proceeds, the commission payable by us to the Agents with respect to such sales and the net proceeds payable to us.

We will disclose the number and average price of the Common Shares sold under this Prospectus Supplement, as well as the gross proceeds, Commission and net proceeds from sales hereunder in our annual and interim financial statements and management's discussion and analysis filed on SEDAR and EDGAR, for any quarters in which sales of Common Shares occur.

Settlement for sales of Common Shares will occur, unless the parties agree otherwise, on the second trading day on the applicable exchange following the date on which any sales were made in return for payment of the net proceeds to us. There is no arrangement for funds to be received in an escrow, trust or similar arrangement. Sales of Common Shares in the U.S. will be settled through the facilities of The Depository Trust Company or by such other means as we and the Agents may agree upon and sales of Common Shares in Canada will be settled through the facilities of CDS Clearing and Depository Services Inc. or by such other means as we and the Agents may agree.

The Canadian Agents will only sell Common Shares on marketplaces in Canada and the U.S. Agents will only sell Common Shares on marketplaces in the U.S.

In connection with the sales of the Common Shares on our behalf, each of the Agents may be deemed to be an "underwriter" within the meaning of the Securities Act, and the compensation paid to the Agents may be deemed to be underwriting commissions or discounts. We have agreed in the Distribution Agreement to provide indemnification and contribution to the Agents against certain liabilities, including liabilities under the Securities Act. In addition, we have agreed to pay the reasonable expenses of the Agents in connection with the Offering, pursuant to the terms of the Distribution Agreement. The Agents and their affiliates will not engage in any transactions to stabilize or maintain the price of our Common Shares in connection with any offer or sales of Common Shares pursuant to the Distribution Agreement. No underwriter or dealer involved in the distribution, no affiliate of such an underwriter or dealer and no person or company acting jointly or in concert with such an underwriter or dealer has over-allotted, or will over-allot, securities in connection with the distribution or effected, or will effect any other transactions that are intended to stabilize or maintain the market price of the securities.

As a consequence of their participation in the offering, the Agents will be entitled to share in the Commission relating to the offering of the Common Shares. We may have outstanding indebtedness owing to certain of the Agents and lending affiliates of such Agents, a portion of which we may reduce or repay with the net proceeds of the Offering. See "Use of Proceeds" and "Relationship with Certain of the Agents". As a result, one or more of such Agents or their affiliates may receive more than 5% of the net proceeds from the Offering in the form of the repayment of such indebtedness. Accordingly, the Offering will be conducted in accordance

S-9

Table of Contents

with Rule 5121 of the Financial Industry Regulatory Authority, Inc., or FINRA. Pursuant to this rule, the appointment of a qualified independent underwriter is not necessary in connection with the Offering, because the conditions of FINRA Rule 5121(a)(1)(B) are satisfied. To comply with FINRA Rule 5121, each of the Agents will not confirm any sales to any account over which it exercises discretionary authority without the specific written approval of the transaction from the account holder.

The total expenses related to the commencement of the Offering to be paid by us, excluding the Commission payable to the Agents under the Distribution Agreement, are estimated to be approximately $1.2 million.

Pursuant to the Distribution Agreement, the Offering will terminate upon the earlier of (i) December 30, 2018, (ii) the issuance and sale of all of the Common Shares subject to the Distribution Agreement, and (iii) the termination of the Distribution Agreement as permitted therein.

We have applied to list the Common Shares offered by this Prospectus Supplement for trading on the TSX and the NYSE. The listing of such Common Shares on the TSX and the NYSE will be subject to our fulfillment of all of the listing requirements of the TSX and the NYSE, respectively.

RELATIONSHIP WITH CERTAIN OF THE AGENTS

Each of the Agents is an affiliate of a financial institution that has, either solely or as a member of a syndicate of financial institutions, extended credit facilities to, or holds other indebtedness of, us and/or our subsidiaries. Consequently, we may be considered a "connected issuer" of the Agents within the meaning of applicable securities legislation. Proceeds from the Offering may be used to reduce indebtedness owed by us to lending affiliates of the Agents or may be invested in short term deposits or securities of or with the Agents or their affiliates. See "Use of Proceeds" and "Plan of Distribution".

The decision to make any distribution of Common Shares pursuant to the Offering and the determination of the terms of the Offering from time to time will be made through negotiation between us and the Agents. No bank has had or will have any involvement in such decision or determination. As at March 23, 2018, an aggregate of approximately $22.4 billion was outstanding under our existing indebtedness, or the Existing Indebtedness, which includes our consolidated long-term debt, capital lease and finance obligations, including current portions, and committed credit facility borrowings classified as long-term debt. We are in material compliance with our respective obligations under the Existing Indebtedness. Since entering into the Existing Indebtedness, no breach thereunder has been waived by the lenders thereof; there has been no material change in our or our subsidiaries' financial position or condition; and the value of any security for any such Existing Indebtedness has not changed, except in the ordinary course of business, or except as otherwise described in this Prospectus Supplement and the Prospectus (including in the documents incorporated by reference herein and therein).

The Agents and/or their affiliates have, from time to time, performed, and may in the future perform, various financial advisory and commercial and investment banking services for us, for which they have received and in the future may receive customary compensation and expense reimbursement. In addition, in the ordinary course of their various business activities, the Agents and/or their affiliates may make or hold a broad array of investments and 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 and may at any time hold long and short positions in such securities and instruments. Such investment and securities activities may involve our securities and instruments. The Agents and/or their affiliates may also make investment recommendations or publish or express independent research views in respect of such securities or instruments and may at any time hold, or recommend to clients that they acquire, long or short positions in such securities and instruments.

S-10

Table of Contents

PRIOR SALES

The following table summarizes our issuances of Common Shares and securities convertible into Common Shares during the 12 months prior to the date of this Prospectus Supplement:

Date	Security	Weighted Average Issue Price or Exercise Price per Security, as applicable

March 1, 2017	Common — DRIP⁽¹⁾	$	41.78	1,503,934
March 1, 2017	Common — ESPP⁽²⁾	$	42.48	140,360
March 1, 2017	Common — CSPP⁽³⁾	$	42.63	7,629
March 3, 2017	Common — Directed Offering	$	41.00	12,195,122
March 2017	Common — Exercise of Stock Options⁽⁴⁾	$	31.19	100,205
March 2017	Common — Conversion of Convertible Debentures⁽⁵⁾	$	30.72	662
April 2017	Common — Exercise of Stock Options⁽⁴⁾	$	32.55	393,045
May 2017	Common — Exercise of Stock Options⁽⁴⁾	$	33.43	170,020
June 1, 2017	Common — DRIP⁽¹⁾	$	43.34	1,450,453
June 1, 2017	Common — ESPP⁽²⁾	$	44.28	136,777
June 1, 2017	Common — CSPP⁽³⁾	$	44.22	7,383
June 2017	Common — Exercise of Stock Options⁽⁴⁾	$	33.32	156,217
August 2017	Common — Exercise of Stock Options⁽⁴⁾	$	35.48	100,847
September 1, 2017	Common — DRIP⁽¹⁾	$	44.83	1,369,415
September 1, 2017	Common — ESPP⁽²⁾	$	45.74	83,295
September 1, 2017	Common — CSPP⁽³⁾	$	45.78	5,724
September 2017	Common — Exercise of Stock Options⁽⁴⁾	$	35.34	6,179
October 2017	Common — Exercise of Stock Options⁽⁴⁾	$	34.09	97,589
November 2017	Common — Exercise of Stock Options⁽⁴⁾	$	33.37	51,656
December 1, 2017	Common — DRIP⁽¹⁾	$	46.78	1,452,118
December 1, 2017	Common — ESPP⁽²⁾	$	47.72	79,446
December 2017	Common — Exercise of Stock Options⁽⁴⁾	$	37.35	5,829
January 2018	Common — Exercise of Stock Options⁽⁴⁾	$	32.95	10,892
February 2018	Common — Exercise of Stock Options⁽⁴⁾	$	33.24	102,556
March 2018	Common — DRIP⁽¹⁾	$	41.08	1,543,414
March 2018	Common — ESPP⁽²⁾	$	41.91	195,214
March 2018	Common — Exercise of Stock Options⁽⁴⁾	$	33.37	58,305

(1): Issued pursuant to our DRIP.
(2): Issued pursuant to our ESPP.
(3): Issued pursuant to our Consumer Share Purchase Plan, which was terminated effective September 13, 2017.
(4): Issued on the exercise of options granted pursuant to our 2006 and 2012 Stock Option Plans.
(5): Issued upon the conversion of the convertible debentures issued by us on January 9, 2014 in connection with the financing of the acquisition of UNS Energy Corporation.

S-11

Table of Contents

TRADING PRICES AND VOLUMES

The following table sets forth, for the periods indicated, the reported high and low daily trading prices and the aggregate volume of trading of our Common Shares on the TSX and the NYSE.

	Trading of Common Shares						Trading of Common Shares

	TSX						NYSE
	High		Low		Volume		High		Low		Volume
	($)		($)		(#)		(US$)		(US$)		(#)
2017
March		44.44		41.95		23,887,789		33.37		31.27		1,854,618
April		45.13		43.70		12,649,620		33.99		32.29		1,036,211
May		45.04		43.12		22,773,180		33.03		31.72		966,730
June		47.06		44.42		20,317,098		35.73		32.91		1,209,849
July		45.66		43.98		13,049,471		36.59		34.25		1,067,510
August		46.43		45.06		15,095,563		36.96		35.73		1,031,598
September		45.80		44.01		18,615,874		37.64		35.33		1,191,801
October		47.78		44.45		13,132,871		37.54		35.62		1,697,605
November		48.73		46.53		14,498,699		38.24		36.13		1,993,741
December		47.96		45.69		15,184,454		37.60		35.77		1,581,609
2018
January		46.00		42.56		23,833,658		36.63		34.49		2,164,264
February		43.48		39.38		27,141,195		35.35		31.41		2,299,440
March 1 to 23		43.68		41.52		20,367,323		34.03		32.29		1,473,325

CERTAIN CANADIAN FEDERAL INCOME TAX CONSIDERATIONS

In the opinion of Davies Ward Phillips & Vineberg LLP, counsel to Fortis, and Stikeman Elliott LLP, counsel to the Agents, or collectively, Counsel, the following summary describes, as of the date of this Prospectus Supplement, the principal Canadian federal income tax considerations pursuant to theIncome Tax Act (Canada), or the Tax Act, generally applicable to a holder who acquires, as beneficial owner, Common Shares pursuant to this offering and who deals at arm's length with us and the Agents for purposes of the Tax Act, or a Holder.

This summary is based upon the provisions of the Tax Act and the regulations thereunder, or the Regulations, in force as of the date hereof, all specific proposals to amend the Tax Act or the Regulations that have been publicly announced prior to the date hereof, or the "Proposed Amendments", and Counsel's understanding of the current published administrative policies and practices of the Canada Revenue Agency. This summary assumes that the Proposed Amendments will be enacted in the form proposed; however, no assurance can be given that the Proposed Amendments will be enacted in the form proposed, if at all. This summary is not exhaustive of all possible Canadian federal income tax considerations and, except for the Proposed Amendments, does not take into account any changes in the law, whether by legislative, governmental or judicial action, nor does it take into account provincial, territorial or foreign tax considerations, which may differ from those discussed herein.

This summary is of a general nature only and is not intended to be, nor should it be construed to be, legal or tax advice to any particular Holder, and no representations with respect to the income tax consequences to any Holder are made. Consequently, Holders and prospective holders of Common Shares should consult their own tax advisors for advice with respect to the tax consequences to them of acquiring Common Shares pursuant to this offering, having regard to their particular circumstances. This summary does not address any tax considerations applicable to persons other than Holders and such persons should consult their own tax advisors regarding the consequences of acquiring, holding and disposing of Common Shares under the Tax Act and any jurisdiction in which they may be subject to tax.

S-12

Table of Contents

Foreign Exchange

For the purposes of the Tax Act, all amounts expressed in a currency other than Canadian dollars relating to the acquisition, holding or disposition of a Common Share, including dividends, adjusted cost base and proceeds of disposition, must be determined in Canadian dollars using the relevant rate of exchange required under the Tax Act.

Residents of Canada

The following summary is generally applicable to a Holder who, at all relevant times for purposes of the Tax Act (a) is, or is deemed to be, resident in Canada, (b) holds Common Shares as "capital property", and (c) is not affiliated with us or the Agents, or a Resident Holder. Generally, Common Shares are considered to be capital property to a Resident Holder unless they are held in the course of carrying on a business or as part of an adventure or concern in the nature of trade. Certain Resident Holders whose Common Shares do not otherwise qualify as capital property may, in certain circumstances, make an irrevocable election in accordance with subsection 39(4) of the Tax Act to have their Common Shares and every other "Canadian security" (as defined in the Tax Act) owned by such holder in the taxation year of the election and in all subsequent taxation years deemed to be capital property. Resident Holders are advised to consult their own tax advisors to determine whether such an election is available and desirable in their particular circumstances.

This summary is not applicable to a Resident Holder: (i) that is a "financial institution" for the purposes of the "mark-to-market" rules contained in the Tax Act; (ii) that is a "specified financial institution"; (iii) an interest in which would be a "tax shelter investment"; (iv) that has elected to report its Canadian tax results in a currency other than the Canadian currency; or (v) that enters into a "derivative forward agreement" in respect of Common Shares, as each of those terms is defined in the Tax Act. Additional considerations, not discussed herein, may apply to a Resident Holder that is a corporation and is, or becomes, or does not deal at arm's length for purposes of the Tax Act with a corporation resident in Canada (the "other Canadian corporation") that is or becomes, as part of a transaction or event or series of transactions or events that include the acquisition of Common Shares, controlled by a non-resident corporation for purposes of the "foreign affiliate dumping" rules in section 212.3 of the Tax Act and in respect of which a subsidiary of Fortis is, or would at any time be, a "foreign affiliate" as defined in the Tax Act of the corporation or the other Canadian corporation. Any such Resident Holder should consult its own tax advisor with respect to an investment in Common Shares.

Dividends

Dividends received or deemed to be received on Common Shares by a Resident Holder who is an individual (other than certain trusts) will be included in computing the individual's income for tax purposes and will be subject to the gross-up and dividend tax credit rules normally applicable to dividends received from "taxable Canadian corporations" (as defined in the Tax Act), including the enhanced gross-up and dividend tax credit in respect of dividends designated by us as "eligible dividends". A dividend will be an eligible dividend if the recipient receives written notice (which may include a notice published on our website) from us designating the dividend as an "eligible dividend". There may be limitations on our ability to designate dividends as "eligible dividends".

Taxable dividends received by a Resident Holder who is an individual (including certain trusts) may give rise to a liability for alternative minimum tax as calculated under the detailed rules set out in the Tax Act. Resident Holders who are individuals should consult their own advisors in this regard.

A Resident Holder that is a corporation will include dividends received or deemed to be received on Common Shares in computing its income for tax purposes and generally will be entitled to deduct the amount of such dividends in computing its taxable income, with the result that no tax will be payable by it in respect of such dividends. In certain circumstances, subsection 55(2) of the Tax Act will treat a taxable dividend received or deemed to be received by a Resident Holder that is a corporation as proceeds of disposition or a capital gain. Resident Holders that are corporations should consult their own tax advisors having regard to their own circumstances.

S-13

Table of Contents

Certain Resident Holders that are corporations, including a "private corporation" or a "subject corporation" (as such terms are defined in the Tax Act), may be liable under Part IV of the Tax Act to pay a refundable tax on dividends received or deemed to be received on the Common Shares to the extent that such dividends are deductible in computing the corporation's taxable income.

Dispositions of Common Shares

A disposition or deemed disposition of a Common Share by a Resident Holder will generally result in the Resident Holder realizing a capital gain (or capital loss) equal to the amount by which the proceeds of disposition of the Common Share, net of any reasonable costs of disposition, are greater (or less) than the Resident Holder's adjusted cost base of the Common Share. Such capital gain (or capital loss) will be subject to the tax treatment described below under "Residents of Canada — Taxation of Capital Gains and Capital Losses".

The amount of any capital loss realized by a Resident Holder that is a corporation on the disposition of a Common Share may be reduced by the amount of certain dividends received or deemed to have been received on such Common Share (or on a share for which such Common Share has been substituted) to the extent and under the circumstances described in the Tax Act. Analogous rules apply to a partnership or trust of which a corporation, trust or partnership is a member or beneficiary. Resident Holders should consult their own tax advisors for specific advice regarding the application of the relevant "stop-loss" provisions in the Tax Act.

The adjusted cost base to the Resident Holder of a Common Share acquired pursuant to this Offering will, at any particular time, be determined in accordance with certain rules in the Tax Act by averaging the cost of such share with the adjusted cost base of all Common Shares owned by the Resident Holder as capital property at that time, if any.

Taxation of Capital Gains and Capital Losses

Generally, one-half of any capital gain, or a taxable capital gain, realized by a Resident Holder in a taxation year must be included in computing the Resident Holder's income for the year, and one-half of any capital loss, or an allowable capital loss, realized by a Resident Holder in a taxation year must be deducted from taxable capital gains realized by the Resident Holder in that year. Allowable capital losses for a taxation year in excess of taxable capital gains for that year generally may be carried back and deducted in any of the three preceding taxation years or carried forward and deducted in any subsequent taxation year against net taxable capital gains realized in such years, to the extent and under the circumstances described in the Tax Act.

Taxable capital gains realized by a Resident Holder who is an individual (including certain trusts) may give rise to liability for alternative minimum tax as calculated under the detailed rules set out in the Tax Act. A Resident Holder that is a "Canadian-controlled private corporation" (as defined in the Tax Act) may be liable to pay an additional refundable tax on certain investment income, including taxable capital gains.

Non-Residents of Canada

The following summary is generally applicable to a Holder who, at all relevant times for purposes of the Tax Act and any applicable tax treaty or convention (a) is not, and is not deemed to be, resident in Canada, and (b) does not use or hold, and is not deemed to use or hold, Common Shares in the course of carrying on a business in Canada, or a Non-Resident Holder. Special rules which are not discussed in this summary may apply to a Non-Resident Holder that is an insurer which carries on an insurance business in Canada and elsewhere.

It is assumed that Common Shares will not be "taxable Canadian property" of a Non-Resident Holder at any time. Generally, Common Shares will not be taxable Canadian property to a Non-Resident Holder at a particular time provided that the Common Shares are listed on a designated stock exchange (such as the TSX or the NYSE) at that time, unless at any time during the 60-month period that ends at that time: (i) one or any combination of (a) the Non-Resident Holder, (b) persons with whom the Non-Resident Holder does not deal at arm's length and (c) partnerships in which the Non-Resident Holder or a person described in (b) holds a membership interest (directly or indirectly through one or more partnerships), own 25% or more of our issued shares of any class or series, and (ii) more than 50% of the fair market value of the Common Shares was derived directly or indirectly from any combination of: (a) real or immovable property situated in Canada, (b) "timber resource property" (within the meaning of the Tax Act), (c) "Canadian resource property" (within the meaning of the Tax Act) or (d) options in respect of, or interests in, or for civil law rights in, any of the foregoing, whether or not the property exists. Notwithstanding the foregoing, in certain circumstances set out in the Tax Act, a Common Share could be deemed to be taxable Canadian property.

S-14

Table of Contents

Dividends

Dividends paid or credited (or deemed to be paid or credited) on Common Shares to a Non-Resident Holder are generally subject to Canadian withholding tax. Under the Tax Act, the rate of withholding tax is 25% of the gross amount of such dividends, which rate may be subject to reduction under the provisions of an applicable tax treaty or convention. Under theCanada-United States Income Tax Convention, or the U.S. Treaty, a Non-Resident Holder who is resident in the U.S. for the purposes of the U.S. Treaty and who is entitled to the benefits of such treaty will generally be subject to Canadian withholding tax at a rate of 15% of the amount of such dividends. In addition, under the U.S. Treaty, dividends may be exempt from Canadian withholding tax if paid to certain Non-Resident Holders that are qualifying religious, scientific, literary, educational or charitable tax-exempt organizations, or are qualifying trusts, companies organizations or other arrangements operated exclusively to administer or provide pension, retirement or employee benefits which are exempt from tax in the U.S., and that have complied with specific administrative procedures.

Dispositions of Common Shares

A Non-Resident Holder will not be subject to tax under the Tax Act on any capital gain realized on a disposition (or deemed disposition) of a Common Share.

CERTAIN U.S. FEDERAL INCOME TAX CONSIDERATIONS

General

In the opinion of Davies Ward Phillips & Vineberg LLP, counsel to Fortis with respect to U.S. federal income tax, the following summary describes the material U.S. federal income tax consequences relating to an investment in the Common Shares. This summary is based on the Internal Revenue Code of 1986, as amended, or the Code, its legislative history, existing final, temporary and proposed Treasury Regulations, rulings and judicial decisions, all as currently in effect and all of which are subject to prospective and retroactive rulings and changes. We will not seek a ruling from the Internal Revenue Service, or the IRS, with regard to the U.S. federal income tax treatment relating to an investment in the Common Shares and, therefore, there can be no assurance that the IRS will agree with the conclusions set forth below.

This summary does not purport to address all U.S. federal income tax consequences that may be relevant to a particular investor and each investor is urged to consult its own tax advisor regarding its specific tax situation. The summary applies only to holders who hold Common Shares as "capital assets" (generally, property held for investment) under the Code, and does not address the tax consequences that may be relevant to investors in special tax situations including, for example:

•: insurance companies;
•: regulated investment companies and real estate investment trusts;
•: tax exempt organizations;
•: broker dealers:
•: traders in securities that elect to mark to market;
•: banks or other financial institutions;
•: investors whose functional currency is not the U.S. dollar;
•: U.S. expatriates;
•: investors that hold the Common Shares as part of a hedge, straddle or conversion transaction;
•: holders that purchase or otherwise acquire Common Shares other than through this Offering; or
•: holders that own, directly, indirectly, or constructively stock representing 10.0% or more of the total combined voting stock or value of Fortis.

S-15

Table of Contents

Further, this summary does not address the alternative minimum tax consequences of an investment in Common Shares or the indirect consequences to holders of equity interests in entities that own the Common Shares. In addition, this summary does not address the state, local and foreign tax consequences of an investment in the Common Shares. Each investor should consult its own tax advisor regarding the U.S. federal, state, local and foreign and other tax consequences of purchasing, owning, and disposing of the Common Shares in its particular circumstances.

An investor is a "U.S. holder" if it is a beneficial owner of Common Shares and is for U.S. federal income tax purposes:

•: an individual citizen or resident alien of the U.S.;
•: a corporation, or any other entity taxable as a corporation, created or organized in or under the laws of the U.S., any state thereof, or the District of Columbia;
•: an estate, the income of which is subject to U.S. federal income tax regardless of its source; or
•: a trust, if a court within the U.S. is able to exercise primary supervision over its administration and one or more U.S. persons have the authority to control all substantial decisions of the trust, or if the trust has made a valid election to be treated as a U.S. person.

If a partnership (or other entity treated as a partnership for U.S. federal income tax purposes) holds Common Shares, the tax treatment of a partner will generally depend upon the status of the partner and upon the activities of the partnership. Partners of partnerships holding Common Shares should consult their own tax advisors.

Dividends on Common Shares

Dividends paid by us to a U.S. holder with respect to Common Shares (including amounts withheld in respect of any Canadian withholding taxes) generally will be taxable to such U.S. holder as ordinary dividend income when such U.S. holder receives the dividend, actually or constructively, to the extent paid out of our current or accumulated earnings and profits (as determined for U.S. federal income tax purposes). Currently, dividends paid by a "qualified foreign corporation" to individual U.S. holders who also meet certain holding period requirements will be taxable at a maximum tax rate of 20%. We expect that Fortis will constitute a qualified foreign corporation for U.S. federal income tax purposes and that distributions it makes to individual U.S. holders that are treated as dividends for U.S. federal income tax purposes will be treated as qualified dividend income eligible for such reduced maximum rates, provided the applicable holding period requirements are met. If distributions by us do not qualify for this reduced maximum rate, U.S. holders will be subject to tax on such distributions at ordinary income rates. Dividends in excess of the current and accumulated earnings and profits of Fortis will be treated first as a non-taxable return of capital reducing such U.S. holder's tax basis in the Common Shares. Any dividends in excess of such tax basis will be treated as capital gain and will be either long-term or short-term capital gain depending upon whether the U.S. holder held the Common Shares for more than one year. Dividends paid by us generally will not be eligible for the dividends-received deduction available to certain U.S. corporate shareholders.

Foreign Tax Credit

Subject to certain limitations, a U.S. holder may be entitled to a credit or deduction against its U.S. federal income taxes for the amount of any Canadian taxes that are withheld from dividend distributions made to such U.S. holder. The decision to claim either a credit or deduction must be made annually and will apply to all foreign taxes paid by the U.S. holder to any foreign country or U.S. possession with respect to the applicable tax year. The limitation on foreign taxes eligible for credit is calculated separately with respect to specific classes of income. Dividends received with respect to the Common Shares will be treated as foreign source income and generally will constitute "passive category income" or "general category income" for U.S. foreign tax credit limitation purposes. The rules regarding the availability of foreign tax credits are complex and U.S. holders may be subject to various limitations on the amount of foreign tax credits that are available. We therefore urge prospective purchasers to consult their own tax advisors regarding the availability of the foreign tax credit under their particular circumstances.

S-16

Table of Contents

The amount of any cash dividend paid in Canadian dollars will equal the U.S. dollar value of the dividend, calculated by reference to the exchange rate in effect at the time the dividend is includable in income by the U.S. holder, regardless of whether the payment is in fact converted to U.S. dollars at that time. Generally, a U.S. holder should not recognize any foreign currency gain or loss if such Canadian dollars are converted into U.S. dollars on the date includable in income. If the Canadian dollars are not converted into U.S. dollars on the date includable in income, however, gain or loss may be recognized upon a subsequent sale or other disposition of the Canadian dollars. Such foreign currency gain or loss, if any, will be U.S. source ordinary income or loss.

Sale, Exchange or Other Disposition of Common Shares

A U.S. holder will generally recognize capital gain or loss upon the sale, exchange or other disposition of the Common Shares measured by the difference between the amount received and the U.S. holder's adjusted tax basis in the Common Shares. Any gain or loss will be long-term capital gain or loss if the Common Shares have been held for more than one year and will generally be U.S. source gain or loss. Long-term capital gains of non-corporate U.S. holders, including individuals, will be eligible for reduced tax rates, currently at a maximum of 20%. A U.S. holder's ability to deduct capital losses is subject to limitations.

For cash-basis U.S. holders who receive foreign currency in connection with a sale, exchange or other disposition of Common Shares, the amount realized will be based upon the U.S. dollar value of the foreign currency received with respect to such Common Shares as determined on the settlement date of such sale, exchange or other disposition. Accrual-basis U.S. holders may elect the same treatment required of cash-basis taxpayers with respect to a sale, exchange or other disposition of Common Shares, provided that the election is applied consistently from year to year. Such election cannot be changed without the consent of the IRS. Accrual-basis U.S. holders that do not elect to be treated as cash-basis taxpayers (pursuant to the Treasury Regulations applicable to foreign currency transactions) for this purpose may have a foreign currency gain or loss for U.S. federal income tax purposes because of differences between the U.S. dollar value of the foreign currency received prevailing on the date of such sale, exchange or other disposition and the value prevailing on the settlement date. Any such currency gain or loss will generally be treated as ordinary income or loss that is U.S. source, in addition to the gain or loss, if any, recognized on the sale, exchange or other disposition of Common Shares.

Passive Foreign Investment Company Rules

U.S. holders generally will be subject to a special, adverse tax regime that would differ in certain respects from the tax treatment described above if we are, or were to become, a passive foreign investment company, or PFIC, for U.S. federal income tax purposes. Although the determination of whether a corporation is a PFIC is made annually based on the facts and circumstances in existence at such time and consequently may be subject to change, we do not believe that Fortis is, nor do we expect Fortis to become, a PFIC for U.S. federal income tax purposes. However, the matter is not free from doubt. We urge holders to consult their own tax advisors regarding the adverse tax consequences of owning the Common Shares were Fortis to be or become a PFIC and certain elections that may be available to lessen those adverse consequences.

Medicare Tax

The U.S. generally imposes a tax of 3.8% on the "net investment income" of certain individuals, trusts and estates. Among other items, net investment income generally includes gross income from interest and dividends as well as net gain attributable to the disposition of certain property, less certain deductions. U.S. holders should consult their own tax advisors regarding the possible implications of this legislation in their particular circumstances.

Backup Withholding and Information Reporting

In general, dividends on Common Shares and payments of the proceeds of a sale, exchange or other disposition of Common Shares, paid to a U.S. holder within the U.S. or through certain U.S.-related financial intermediaries, are subject to information reporting requirements and may be subject to backup withholding at a rate currently equal to 24% unless the holder is a corporation or other exempt recipient, or provides an accurate

S-17

Table of Contents

taxpayer identification number and certifies that no loss of exemption from backup withholding has occurred. U.S. holders who are required to establish their exempt status must provide such certification on IRS Form W-9.

Backup withholding is not an additional tax. A holder generally will be allowed a credit of the amount of any backup withholding against its U.S. federal income tax liability or may obtain a refund of any amounts withheld under the backup withholding rules that exceed the holder's income tax liability by timely filing a refund claim with the IRS.

U.S. return disclosure obligations (and related penalties for failure to disclose) apply to certain U.S. individuals who hold specified foreign financial assets if the total value of all such assets is more than US$50,000 on the last day of the tax year or more than US$75,000 at any time during the tax year. The definition of specified foreign financial assets may include the Common Shares. U.S. holders should consult their own tax advisors regarding the application of these disclosure obligations. U.S. holders may be required to make various tax filings with respect to their investments in the Common Shares, including, among others, IRS Form 926 (Return by a U.S. Transferor of Property to a Foreign Corporation).

LEGAL MATTERS

Certain legal matters relating to this Offering will be passed upon on our behalf by Davies Ward Phillips & Vineberg LLP, Toronto, Ontario and Davies Ward Phillips & Vineberg LLP, New York, New York and on behalf of the Agents, with respect to certain legal matters relating to Canadian law, by Stikeman Elliott LLP, Toronto, Ontario, and, with respect to certain legal matters relating to U.S. law, by Paul, Weiss, Rifkind, Wharton & Garrison LLP, Toronto, Ontario and New York, New York. At the date hereof, partners and associates of each of Davies Ward Phillips & Vineberg LLP and Stikeman Elliott LLP own beneficially, directly or indirectly, less than 1% of any of our securities or any securities of our associates or affiliates.

EXPERTS

The Annual Financial Statements have been incorporated by reference in this Prospectus Supplement and in the registration statement including the related audit reports of Deloitte LLP, our current auditor, and Ernst & Young LLP, our former auditor.

Our audited consolidated financial statements as at December 31, 2017 and for the fiscal year then ended, and the effectiveness of our internal control over financial reporting, have been audited by Deloitte LLP, an independent registered public accounting firm, as stated in their reports, which are incorporated herein by reference. Such consolidated financial statements have been so incorporated in reliance upon the reports of such firm given upon their authority as experts in accounting and auditing. Deloitte LLP is independent of us within the meaning of the Rules of Professional Conduct of the Chartered Professional Accountants of Newfoundland and Labrador and within the meaning of the applicable rules and regulations adopted by the Public Company Accounting Oversight Board (United States) and the SEC.

Our audited comparative consolidated financial statements as at December 31, 2016 and for the fiscal year then ended have been audited by Ernst & Young LLP, a registered public accounting firm, as stated in their auditor report thereon which is incorporated herein by reference. Such consolidated financial statements have been so incorporated in reliance upon the reports of such firm given upon their authority as experts in accounting and auditing.

ENFORCEABILITY OF CIVIL LIABILITIES

We are continued under the laws of the Province of Newfoundland and Labrador, Canada. The majority of our directors and officers, and some of the experts named in this Prospectus, are residents of Canada, and all or a substantial portion of their assets, and a substantial portion of our assets, are located outside the U.S. We have appointed an agent for service of process in the U.S., but it may be difficult for holders of Common Shares who reside in the U.S. to effect service within the U.S. upon those directors, officers and experts who are not residents of the U.S. It may also be difficult for holders of the Common Shares who reside in the U.S. to realize in the U.S. upon judgments of courts of the U.S. predicated upon our civil liability and the civil liability of our directors and officers and experts under U.S. federal securities laws.

S-18

Table of Contents

We have filed with the SEC an appointment of agent for service of process on Form F-X. Under the Form F-X, we have appointed CT Corporation System, 111 Eighth Avenue, New York, New York 10011, as our agent for service of process in the U.S. in connection with any investigation or administrative proceeding conducted by the SEC, and any civil suit or action brought against us in a U.S. court arising out of or related to or concerning the offering of securities under the registration statement of which this Prospectus Supplement forms a part.

We have been advised by our Canadian counsel, Davies Ward Phillips & Vineberg LLP, that a judgment of a U.S. court predicated solely upon civil liability under U.S. federal securities laws would probably be enforceable in Canada if the U.S. court in which the judgment was obtained has a basis for jurisdiction in the matter that would be recognized by a Canadian court for the same purposes. We have also been advised by Davies Ward Phillips & Vineberg LLP, however, that there is real doubt whether an action could be brought in Canada in the first instance on the basis of liability predicated solely upon U.S. federal securities laws.

Four of our directors, Mr. Lawrence T. Borgard, Ms. Maura J. Clark, Ms. Margarita K. Dilley and Mr. Joseph L. Welch, reside outside of Canada and each has appointed Fortis Inc., Suite 1100, 5 Springdale Street, P.O. Box 8837, St. John's, Newfoundland and Labrador A1B 3T2 as agent for service of process. You are advised that it may not be possible to enforce judgments obtained in Canada against any person that resides outside of Canada, even if such person has appointed an agent for service of process.

AUDITOR

Our auditor is Deloitte LLP, 5 Springdale Street, Suite 1000, St. John's, Newfoundland and Labrador A1E 0E4.

DOCUMENTS FILED AS PART OF THE REGISTRATION STATEMENT

The following documents have been or will be filed with the SEC as part of the registration statement of which this Prospectus Supplement forms a part: the documents referred to under "Documents Incorporated by Reference"; consent of Deloitte LLP; consent of Ernst & Young LLP; consent of Davies Ward Phillips & Vineberg LLP; consent of Stikeman Elliott LLP; and powers of attorney from directors and officers of the Corporation.

S-19

Table of Contents

Information has been incorporated by reference in this short form base shelf prospectus from documents filed with securities commissions or similar authorities in each of the provinces of Canada.Copies of the documents incorporated herein by reference may be obtained on request without charge from the Corporate Secretary of Fortis at Suite 1100, 5 Springdale Street, P.O. Box 8837, St. John's, Newfoundland and Labrador A1B 3T2 (telephone (709) 737-2800) and are also available electronically atwww.sedar.com.

SHORT FORM BASE SHELF PROSPECTUS


New Issue and/or Secondary Offering		November 30, 2016

FORTIS INC.

$5,000,000,000

COMMON SHARES
FIRST PREFERENCE SHARES
SECOND PREFERENCE SHARES
SUBSCRIPTION RECEIPTS
DEBT SECURITIES

We may from time to time offer and issue common shares, or Common Shares, first preference shares, or First Preference Shares, second preference shares, or Second Preference Shares, subscription receipts, or Subscription Receipts, and/or unsecured debt securities, or Debt Securities, and together with the Common Shares, First Preference Shares, Second Preference Shares and Subscription Receipts, the Securities, having an aggregate offering price of up to $5,000,000,000 (or the equivalent in U.S. dollars or other currencies), during the 25 month period that this short form base shelf prospectus, or the Prospectus, including any amendments hereto, remains valid. Securities may be offered separately or together, in amounts, at prices and on terms to be determined based on market conditions at the time of sale and set forth in an accompanying prospectus supplement, or a Prospectus Supplement.

We are permitted, under the multi-jurisdictional disclosure system adopted by the United States, or the U.S., and Canada, to prepare this Prospectus in accordance with Canadian disclosure requirements. You should be aware that such requirements are different from those of the U.S.

Financial statements incorporated by reference herein have been prepared in accordance with U.S. generally accepted accounting principles, or U.S. GAAP.

Prospective investors should be aware that the acquisition of Securities may subject you to tax consequences in both the U.S. and Canada. This Prospectus may not describe these tax consequences fully. You should read the tax discussion contained in any applicable Prospectus Supplement.

Your ability to enforce civil liabilities under U.S. federal securities laws may be affected adversely because our company is incorporated under the laws of the Province of Newfoundland and Labrador, Canada, some of our officers and directors and some of the experts named in this Prospectus are non-U.S. residents, and some of our assets and some of the assets of those officers, directors and experts may be located outside of the U.S.

THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE U.S. SECURITIES AND EXCHANGE COMMISSION, OR THE SEC, NOR HAS THE SEC PASSED UPON THE ADEQUACY OR ACCURACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

No underwriter or dealer has been involved in the preparation of, or has performed any review of, this Prospectus.

The specific variable terms of any offering of Securities will be set out in the applicable Prospectus Supplement including, where applicable: (a) in the case of Common Shares, the number of shares offered and the offering price (or the manner of determination thereof if offered on a non-fixed price basis); (b) in the case of First Preference Shares and Second Preference Shares, the designation of the particular series, the number of shares offered, the offering price (or the manner of determination thereof if offered on a non-fixed price basis), the currency or currency unit for which such shares may be purchased, any voting rights, any rights to receive dividends, any terms of redemption, any

Table of Contents

conversion or exchange rights and any other specific terms; (c) in the case of Subscription Receipts, the offering price (or the manner of determination thereof if offered on a non-fixed price basis), the procedures for the exchange of Subscription Receipts for Common Shares, First Preference Shares, Second Preference Shares or Debt Securities, as the case may be, and any other specific terms; and (d) in the case of Debt Securities, the designation of the Debt Securities, the aggregate principal amount of the Debt Securities being offered, the currency or currency unit in which the Debt Securities may be purchased, authorized denominations, any limit on the aggregate principal amount of the Debt Securities of the series being offered, the issue and delivery date, the maturity date, the offering price (at par, at a discount or at a premium), the interest rate or method of determining the interest rate, the interest payment date(s), any conversion or exchange rights that are attached to the Debt Securities, any redemption provisions, any repayment provisions and any other specific terms. A Prospectus Supplement may include other specific variable terms pertaining to the Securities that are not within the alternatives and parameters described in this Prospectus.

All shelf information permitted under applicable laws to be omitted from this Prospectus will be contained in one or more Prospectus Supplements that will be delivered to purchasers together with this Prospectus. Each Prospectus Supplement will be incorporated by reference into this Prospectus for the purposes of securities legislation as of the date of the Prospectus Supplement and only for the purposes of the distribution of the Securities to which the Prospectus Supplement pertains.

We may sell the Securities to or through underwriters or dealers purchasing as principals and may also sell the Securities to one or more purchasers directly subject to obtaining any required exemptive relief or through agents. The Prospectus Supplement relating to a particular offering of Securities will identify each underwriter, dealer or agent, if any, engaged by us in connection with the offering and sale of Securities and will set forth the terms of the offering of such Securities, the method of distribution of such Securities including, to the extent applicable, the proceeds to us, and any fees, discounts or any other compensation payable to underwriters, dealers or agents and any other material terms of the plan of distribution. Securities may be sold from time to time in one or more transactions at a fixed price or fixed prices, or at non-fixed prices. If offered on a non-fixed price basis, Securities may be offered at market prices prevailing at the time of sale or at prices to be negotiated with purchasers at the time of sale, which prices may vary between purchasers and during the period of distribution. If Securities are offered on a non-fixed price basis, the underwriters', dealers' or agents' compensation will be increased or decreased by the amount by which the aggregate price paid for Securities by the purchasers exceeds or is less than the gross proceeds paid by the underwriters, dealers or agents to us. See "Plan of Distribution".

This Prospectus also qualifies the distribution of Securities by certain of our securityholders, including one or more of our wholly owned subsidiaries, or each a Selling Securityholder. One or more Selling Securityholders may sell Securities to or through underwriters or dealers purchasing as principals and may also sell the Securities to one or more purchasers directly, through statutory exemptions, or through agents designated from time to time. See "Plan of Distribution" and "Selling Securityholders".

Our Common Shares, First Preference Shares, Series F, First Preference Shares, Series G, First Preference Shares, Series H, First Preference Shares, Series I, First Preference Shares, Series J, First Preference Shares, Series K and First Preference Shares, Series M are listed on the Toronto Stock Exchange, or TSX, under the symbols "FTS", "FTS.PR.F", "FTS.PR.G", "FTS.PR.H", "FTS.PR.I", "FTS.PR.J", "FTS.PR.K" and "FTS.PR.M", respectively. Our Common Shares are listed on the New York Stock Exchange, or NYSE, under the symbol "FTS".There is currently no market through which the First Preference Shares, Second Preference Shares, Subscription Receipts or Debt Securities may be sold and purchasers may not be able to resell any First Preference Shares, Second Preference Shares, Subscription Receipts or Debt Securities purchased under this Prospectus. This may affect the pricing of such Securities in the secondary market, the transparency and availability of trading prices, the liquidity of such Securities and the extent of issuer regulation. See the "Risk Factors" section of the applicable Prospectus Supplement.

This Prospectus does not qualify for issuance Debt Securities in respect of which the payment of principal and/or interest may be determined, in whole or in part, by reference to one or more underlying interests including, for example, an equity or debt security, a statistical measure of economic or financial performance including, but not limited to, any currency, consumer price or mortgage index, or the price or value of one or more commodities, indices or other items, or any other item or formula, or any combination or basket of the foregoing items. For greater certainty, this Prospectus may qualify for issuance Debt Securities in respect of which the payment of principal and/or interest may be determined, in whole or in part, by reference to published rates of a central banking authority or one or more financial institutions, such as a prime rate or bankers' acceptance rate, or to recognized market benchmark interest rates such as LIBOR, EURIBOR or a U.S. federal funds rate.

Subject to applicable laws, in connection with any offering of Securities, the underwriters, dealers or agents may over-allot or effect transactions which stabilize or maintain the market price of the Securities at levels other than those which may prevail on the open market. Such transactions, if commenced, may be interrupted or discontinued at any time. See "Plan of Distribution".

Table of Contents

TABLE OF CONTENTS

		Page

NOTICE TO READERS		2
SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS		2
DOCUMENTS FILED AS PART OF THE REGISTRATION STATEMENT		4
DOCUMENTS INCORPORATED BY REFERENCE		4
WHERE YOU CAN FIND ADDITIONAL INFORMATION		6
PRESENTATION OF FINANCIAL INFORMATION		6
CURRENCY AND EXCHANGE RATE INFORMATION		7
FORTIS		7
SHARE CAPITAL OF FORTIS		8
EARNINGS COVERAGE RATIOS		8
DIVIDEND POLICY		9
DESCRIPTION OF SECURITIES OFFERED		10
CHANGES IN SHARE AND LOAN CAPITAL STRUCTURE		16
PRIOR SALES		17
TRADING PRICES AND VOLUMES		18
USE OF PROCEEDS		20
PLAN OF DISTRIBUTION		20
SELLING SECURITYHOLDERS		21
CERTAIN INCOME TAX CONSIDERATIONS		22
RISK FACTORS		22
AUDITORS		24
LEGAL MATTERS		24
ENFORCEABILITY OF CIVIL LIABILITIES		24
GLOSSARY		25

Table of Contents

NOTICE TO READERS

Investors should rely only on the information contained in or incorporated by reference in this Prospectus or any applicable Prospectus Supplement. We have not authorized anyone to provide investors with different or additional information. We are not making an offer of Securities in any jurisdiction where the offer is not permitted by law. Prospective investors should not assume that the information contained in or incorporated by reference in this Prospectus or any applicable Prospectus Supplement is accurate as of any date other than the date on the front of the applicable Prospectus Supplement.

Unless we have indicated otherwise, or the context otherwise requires, references in this Prospectus to "Fortis", "we", "us" and "our" refer to Fortis Inc. and our consolidated subsidiaries.

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

Capitalized terms used but not otherwise defined in this "Special Note Regarding Forward-Looking Statements" have the meanings ascribed thereto under the heading "Glossary".

This Prospectus, including the documents incorporated herein by reference, contains "forward-looking information" within the meaning of applicable Canadian securities laws and "forward-looking statements" within the meaning of theU.S. Private Securities Litigation Reform Act of 1995 (collectively referred to herein as "forward-looking information" or "forward-looking statements"). The forward-looking information reflects our current expectations regarding our future growth, results of operations, performance, business prospects and opportunities, based on information currently available. These expectations may not be appropriate for other purposes. All forward-looking information is given pursuant to the "safe harbour" provisions of applicable Canadian securities legislation. The words "anticipates", "assumes", "believes", "budgets", "can", "could", "estimates", "expects", "forecasts", "intends", "may", "might", "opportunity", "plans", "projects", "seeks", "schedule", "should", "target", "will", "would" and similar expressions are often intended to identify forward-looking information, although not all forward-looking information contains these identifying words. The forward-looking information reflects management's current beliefs and is based on information currently available to us.

The forward-looking information in this Prospectus, including the documents incorporated herein by reference, includes, but is not limited to, statements regarding: the expectation that the acquisition of ITC will be accretive to earnings per Common Share in the first full year following closing, excluding one-time acquisition-related expenses; the expectation that we will recognize additional acquisition-related expenses in the fourth quarter of 2016; targeted average annual dividend growth through 2021; the expected timing of filing of regulatory applications and receipt and outcome of regulatory decisions; our forecast midyear rate base for 2017 and the expectation that midyear rate base will increase from 2016 to 2021; forecast gross consolidated capital expenditures for 2016 and total capital spending through 2021; forecast gross consolidated capital expenditures for 2016 for certain of our subsidiaries, including ITC, FortisAlberta and UNS Energy; the nature, timing and expected costs of certain capital projects including, without limitation, expansion of the Tilbury LNG facility, including Tilbury 1A, the pipeline expansion to the Woodfibre LNG site, and additional opportunities including electric transmission, LNG and renewable-related infrastructure and generation; the expectation that our significant capital expenditure program will support continuing growth in earnings and dividends; the expectation that the acquisition of ITC will increase total capitalization, but will not have a significant impact on the percentage breakdown of our capital structure; the expectation that cash required to complete subsidiary capital expenditure programs will be sourced from a combination of cash from operations, borrowings under credit facilities, equity injections from us and long-term debt offerings; the expectation that maintaining the targeted capital structure of our regulated operating subsidiaries will not have an impact on its ability to pay dividends in the foreseeable future; the expectation that our subsidiaries will be able to source the cash required to fund our 2016 capital expenditure programs; the expected consolidated fixed-term debt maturities and repayments over the next five years, including at ITC; the expectation that the combination of available credit facilities and relatively low annual debt maturities and repayments will provide us with flexibility in the timing of access to capital markets; the expectation that we will remain compliant with debt covenants throughout 2016; the intent of management to hedge future exchange rate fluctuations and monitor our foreign currency exposure; the expectation that FortisAlberta will recognize capital tracker revenue in 2016; Tucson Electric

Table of Contents

Power Company's expected share of mine reclamation costs; Central Hudson's estimated total remediation costs for manufactured gas plant sites; the estimated range of return on common shareholder's equity refunds and associated regulatory liabilities at ITC; the expectation that any liability from current legal proceedings will not have a material adverse effect on our consolidated financial position and results of operations; and the expectation that the adoption of certain future accounting pronouncements will not have a material impact on our consolidated financial statements.

The forecasts and projections that make up the forward-looking information included in this Prospectus are based on assumptions which include, but are not limited to: the realization of the anticipated benefits of the acquisition of ITC; our ability to successfully integrate the business and operations of ITC into our group of companies; our ability to retain key employees of ITC; the absence of undisclosed liabilities of ITC; the receipt of applicable regulatory approvals and requested rate orders, no material adverse regulatory decisions being received, and the expectation of regulatory stability; no material capital project and financing cost overrun related to any of our capital projects; the realization of additional opportunities including natural gas related infrastructure and generation; our Board of Directors exercising its discretion to declare dividends, taking into account our business performance and financial conditions; no significant variability in interest rates; no significant operational disruptions or environmental liability due to a catastrophic event or environmental upset caused by severe weather, other acts of nature or other major events; the continued ability to maintain the electricity and gas systems to ensure their continued performance; no severe and prolonged downturn in economic conditions; no significant decline in capital spending; sufficient liquidity and capital resources; the continuation of regulator-approved mechanisms to flow through the cost of natural gas and energy supply costs in customer rates; the ability to hedge exposures to fluctuations in foreign exchange rates, natural gas prices and electricity prices; no significant counterparty defaults; the continued competitiveness of natural gas pricing when compared with electricity and other alternative sources of energy; the continued availability of natural gas, fuel, coal and electricity supply; continuation and regulatory approval of power supply and capacity purchase contracts; the ability to fund defined benefit pension plans, earn the assumed long-term rates of return on the related assets and recover net pension costs in customer rates; no significant changes in government energy plans, environmental laws and regulations that may materially negatively affect our operations and cash flows; no material change in public policies and directions by governments that could materially negatively affect us and our subsidiaries; maintenance of adequate insurance coverage; the ability to obtain and maintain licences and permits; retention of existing service areas; the continued tax-deferred treatment of earnings from our Caribbean operations; continued maintenance of information technology infrastructure; continued favourable relations with First Nations; favourable labour relations; that we can reasonably assess the merit of and potential liability attributable to ongoing legal proceedings; and sufficient human resources to deliver service and execute the capital program.

The forward-looking information is subject to risks, uncertainties and other factors that could cause actual results to differ materially from historical results or results anticipated by the forward-looking information. Factors which could cause results or events to differ from current expectations include, but are not limited to: regulatory risk, including risks relating to pending and future changes in environmental regulations; interest rate risk, including the uncertainty of the impact that a continuation of a low interest rate environment may have on the ROE of our regulated utilities; the impact of fluctuations in foreign exchange rates; risk associated with the impact of less favorable economic conditions on our results of operations; risks associated with the continuation, renewal, replacement and/or regulatory approval of power supply and capacity purchase contracts; risks relating to energy prices; provincial, state and federal regulatory legislative decisions and actions; uncertainty related to the realization of some or all of the expected benefits of the acquisition of ITC; uncertainty regarding the outcome of regulatory proceedings of our utilities; risks relating to any potential downgrade of our credit ratings; risks relating to the Base Rate Complaints; risks relating to potential additional FERC challenges and FERC orders that could result in the ITC Regulated Operating Subsidiaries continuing to take Bonus Depreciation; operating and maintenance risks, including our limited experience in the independent FERC-regulated transmission industry; the risk that ITC will not be integrated successfully; risks relating to our ability to access capital markets on favourable terms or at all; the cost of debt and equity capital; risks associated with changes in economic conditions; changes in regional economic and market conditions which could affect customer growth and energy usage; risks relating to the impact of actual loads, forecasted loads, regional economic conditions, weather conditions, union strikes, labour shortages, material and equipment prices and

Table of Contents

availability; the performance of the stock market and changing interest rate environment; risks from regulatory approvals for reasons relating to rate construct, environmental, siting, regional planning, cost recovery or other issues or as a result of legal proceedings; risks arising from variances between estimated and actual costs of construction contracts awarded and the potential for greater competition; insurance coverage risk; risk of loss of licences and permits; risk of loss of service area; risks relating to derivatives; the continued ability to hedge foreign exchange risk; counterparty risk; environmental risks; competitiveness of natural gas; natural gas, fuel, coal and electricity supply risk; risks relating to human resources and labour relations; risk of unexpected outcomes of legal proceedings currently against us; risk of not being able to access First Nations lands; weather and seasonality risk; commodity price risk; capital resources and liquidity risks; changes in critical accounting estimates; risks related to changes in tax legislation; the ongoing restructuring of the electric industry; changes to long-term contracts; risk of failure of information technology infrastructure and cyber-attacks or challenges to our information security; and certain presently unknown or unforeseen risks, including, but not limited to, acts of terrorism. For additional information with respect to our risk factors and risk factors relating to ITC, the acquisition of ITC and our post-acquisition business and operations, reference should be made to the section of this Prospectus entitled "Risk Factors", to the documents incorporated herein by reference and to our continuous disclosure materials filed from time to time with Canadian and U.S. securities regulatory authorities.

All forward-looking information in this Prospectus and in the documents incorporated herein by reference is qualified in its entirety by the above cautionary statements and, except as required by law, we undertake no obligation to revise or update any forward-looking information as a result of new information, future events or otherwise.

DOCUMENTS FILED AS PART OF THE REGISTRATION STATEMENT

The following documents have been filed with the SEC as part of our registration statement: (a) the documents referred to under the heading "Documents Incorporated by Reference"; (b) the consent of Ernst & Young LLP; (c) the consent of Deloitte & Touche LLP; (d) the consent of Davies Ward Phillips & Vineberg LLP; (e) the power of attorney of the directors and officers of Fortis; and (f) the Statement of Eligibility on Form T-1 under theU.S. Trust Indenture Act of 1939 of The Bank of New York Mellon.

DOCUMENTS INCORPORATED BY REFERENCE

Information has been incorporated by reference in this Prospectus from documents filed by us with securities commissions or similar authorities in Canada. Our disclosure documents listed below and filed with the appropriate securities commissions or similar regulatory authorities in each of the provinces of Canada are specifically incorporated by reference into and form an integral part of this Prospectus:

(a)

our Annual Information Form dated February 17, 2016, for the fiscal year ended December 31, 2015;

(b)

our audited comparative consolidated financial statements as at December 31, 2015 and December 31, 2014 and for the fiscal years ended December 31, 2015 and 2014, together with the notes thereto, or the Annual Financial Statements, and the auditors' report thereon dated February 17, 2016;

(c)

our Management Discussion and Analysis of financial condition and results of operations dated February 17, 2016 for the fiscal year ended December 31, 2015, or the Annual MD&A;

(d)

our Management Information Circular dated March 18, 2016 prepared in connection with our annual and special meeting of shareholders held on May 5, 2016, or the Management Information Circular; provided, however, that the following sections or subsections of the Management Information Circular are hereby excluded from this Prospectus in accordance with Item 11.1(3) of Form 44-101F1 — Short Form Prospectus as the acquisition of ITC Holdings Corp., or ITC, has been completed:

(i): "Questions and Answers About the Meeting and Acquisition — Did the Board of Directors of Fortis receive a fairness opinion in connection with the Acquisition?" at pages 3-4 of the Management Information Circular;
(ii): the references to Goldman, Sachs & Co. and the opinion of Goldman, Sachs & Co. under the headings "Special Business — The Acquisition of ITC Holdings Corp. — Background and

Table of Contents

Recommendation — Background to the Acquisition" and "Special Business — The Acquisition of ITC Holdings Corp. — Background and Recommendation — Recommendation of the Board" at page 19 of the Management Information Circular;

(iii): Schedule C — Opinion of Goldman, Sachs & Co.; and
(iv): any other references to Goldman, Sachs & Co. and the opinion of Goldman, Sachs & Co. contained in the Management Information Circular;

(e): our unaudited comparative interim consolidated financial statements as at September 30, 2016 and for the three and nine months ended September 30, 2016 and 2015, together with the notes thereon, or the Interim Financial Statements;
(f): our Management Discussion and Analysis of financial condition and results of operations for the three and nine months ended September 30, 2016, or the Interim MD&A;
(g): our material change report dated February 11, 2016 relating to the announcement of the acquisition of ITC;
(h): our material change report dated October 24, 2016 relating to the announcement of the completion of the acquisition of ITC; and
(i): our business acquisition report dated November 23, 2016 with respect to the acquisition of ITC completed on October 14, 2016, or the ITC Business Acquisition Report.

Any document of the type referred to above, including any material change report (other than any confidential material change report), any business acquisition report, any Prospectus Supplements disclosing additional or updated information, and any "template version" of "marketing materials" (each as defined in National Instrument 41-101 — General Prospectus Requirements) subsequently filed by us with such securities commissions or regulatory authorities in Canada after the date of this Prospectus, and prior to the termination of the distribution under this Prospectus, shall be deemed to be incorporated by reference into this Prospectus.

Documents filed by us with the SEC or similar authorities in Canada which are in our current reports on Form 6-K or annual reports on Form 40-F under theU.S. Securities Exchange Act of 1934, as amended, or the Exchange Act, in each case after the date of this Prospectus, shall be deemed to be incorporated by reference as exhibits to the registration statement of which this Prospectus forms a part and, in addition, any other report on Form 6-K and the exhibits thereto shall be deemed to be incorporated by reference into this Prospectus or as exhibits to the registration statement, if and to the extent expressly provided in such reports. Our current reports on Form 6-K and our annual reports on Form 40-F are available on the SEC's Electronic Data Gathering and Retrieval, or EDGAR, website at www.sec.gov.

Any statement contained in a document incorporated or deemed to be incorporated by reference in this Prospectus shall be deemed to be modified or superseded for purposes of this Prospectus to the extent that a statement contained herein, or in any other subsequently filed document which also is incorporated or is deemed to be incorporated by reference herein, modifies or supersedes such statement. The modifying or superseding statement need not state that it has modified or superseded a prior statement or include any other information set forth in the document that it modifies or supersedes. The making of a modifying or superseding statement will not be deemed an admission for any purpose that the modified or superseded statement, when made, constituted a misrepresentation, an untrue statement of a material fact or an omission to state a material fact that is required to be stated or that is necessary to make a statement not misleading in light of the circumstances in which it was made. Any statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of this Prospectus.

When we file a new annual information form and audited consolidated financial statements and related management discussion and analysis with, and where required, they are accepted by, the applicable securities regulatory authorities during the time that this Prospectus is valid, the previous annual information form, the previous audited consolidated financial statements and related management discussion and analysis and all unaudited interim consolidated financial statements and related management discussion and analysis for such periods, all material change reports and any information circular and business acquisition report filed prior to

Table of Contents

the commencement of our financial year in which the new annual information form is filed will be deemed no longer to be incorporated by reference in this Prospectus for purposes of future offers and sales of Securities under this Prospectus. Upon new interim financial statements and the accompanying management discussion and analysis being filed by us with the applicable securities regulatory authorities during the term of this Prospectus, all interim financial statements and accompanying management's discussion and analysis filed prior to the filing of the new interim financial statements shall be deemed no longer to be incorporated by reference into this Prospectus for purposes of future offers and sales of Securities hereunder.

Copies of the documents incorporated herein by reference may be obtained on request without charge from our Corporate Secretary at Suite 1100, 5 Springdale Street, P.O. Box 8837, St. John's, Newfoundland and Labrador A1B 3T2 (telephone (709) 737-2800). These documents are also available through the Internet on our website atwww.fortisinc.com or on SEDAR, which can be accessed atwww.sedar.com. The information contained on, or accessible through, any of these websites is not incorporated by reference into this Prospectus and is not, and should not be considered to be, a part of this Prospectus, unless it is explicitly so incorporated.

WHERE YOU CAN FIND ADDITIONAL INFORMATION

We have filed with the SEC a registration statement on Form F-10 under theU.S. Securities Act of 1933, as amended, or the Securities Act, with respect to the Securities offered by this Prospectus as supplemented by a Prospectus Supplement. This Prospectus, which forms a part of the registration statement, does not contain all of the information set forth in the registration statement, certain parts of which have been omitted in accordance with the rules and regulations of the SEC. For further information with respect to us and the Securities offered in this Prospectus, reference is made to the registration statement and to the schedules and exhibits filed therewith. Statements contained in this Prospectus as to the contents of certain documents are not necessarily complete and, in each instance, reference is made to the copy of the document filed as an exhibit to the registration statement. Each such statement is qualified in its entirety by such reference.

PRESENTATION OF FINANCIAL INFORMATION

Financial statements incorporated by reference herein have been prepared in accordance with U.S. GAAP.

All financial information of ITC and the historical financial statements of ITC incorporated by reference in this Prospectus are reported in U.S. dollars and have been prepared in accordance with U.S. GAAP. Our unaudited pro forma condensed consolidated financial information included in the ITC Business Acquisition Report incorporated by reference in this Prospectus are reported in Canadian dollars and have been prepared in accordance with applicable Canadian rules. The assets and liabilities of ITC shown in our unaudited pro forma condensed consolidated balance sheet as at September 30, 2016 included in the ITC Business Acquisition Report are reported in Canadian dollars and reflect the U.S.-to-Canadian dollar period-end closing exchange rate. The revenues and expenses of ITC shown in our unaudited pro forma condensed consolidated statement of earnings for the year ended December 31, 2015 and for the nine months ended September 30, 2016, included in the ITC Business Acquisition Report, are reported in Canadian dollars and reflect the average U.S.-to-Canadian dollar exchange rates for such periods. Financial information in this Prospectus that has been derived from such unaudited pro forma condensed consolidated financial information has been translated to Canadian dollars on the same basis.

Table of Contents

Certain calculations included in tables and other figures in this Prospectus have been rounded for clarity of presentation.

CURRENCY AND EXCHANGE RATE INFORMATION

This Prospectus contains references to U.S. dollars and Canadian dollars. All dollar amounts referenced, unless otherwise indicated, are expressed in Canadian dollars. References to "$" or "C$" are to Canadian dollars and references to "US$" are to U.S. dollars. The following table shows, for the years and dates indicated, certain information regarding the Canadian dollar/U.S. dollar exchange rate. The information is based on the noon exchange rate as reported by the Bank of Canada. Such exchange rate on November 28, 2016 was C$1.3401 = US$1.00.

		Average⁽¹⁾

		(C$ per US$)
Year ended December 31,
2015	1.3840		1.2788	1.1728	1.3990
2014	1.1601		1.1045	1.0614	1.1643
2013	1.0636		1.0299	0.9839	1.0697
Quarter ended,
September 30, 2016				1.2775	1.3248
June 30, 2016				1.2544	1.3170
March 31, 2016				1.2962	1.4589

(1): The average of the noon buying rates during the relevant period.

FORTIS

We are an international electric and gas utility holding company, with total assets of approximately $47 billion, on a pro forma basis as at September 30, 2016 including the acquisition of ITC, and revenue totaling approximately $8.1 billion and $5.8 billion for the year ended December 31, 2015 and the nine months ended September 30, 2016, respectively, in each case on a pro forma basis including the acquisition of ITC. In 2015, our electricity distribution systems met a combined peak demand of 9,705 megawatts, or MW, and our gas distribution systems met a peak day demand of 1,323 terajoules, or TJ. For the nine months ended September 30, 2016, our electricity distribution systems met a combined peak demand of 9,590 MW and our gas distribution system met a peak day demand of 1,335 TJ. In addition, ITC's electricity transmission system serves a combined peak load exceeding 26,000 MW. Our 8,000 employees serve customers at utility operations in five Canadian provinces, nine U.S. states and three Caribbean countries.

Our business segments are:

(a): Regulated Independent Transmission — United States: consisting of the electric transmission operations of ITC, acquired by us and GIC Pte Ltd, or GIC, on October 14, 2016. ITC is now our indirect subsidiary, with Eiffel Investment Pte Ltd (an affiliate of GIC) owning a 19.9% interest in ITC. ITC's business consists primarily of the electric transmission operations of ITC's regulated operating subsidiaries, which include International Transmission Company, Michigan Electric Transmission Company, LLC, ITC Midwest LLC, ITC Great Plains, LLC and ITC Interconnection LLC. ITC owns and operates high-voltage transmission facilities in Michigan, Iowa, Minnesota, Illinois, Missouri, Kansas and Oklahoma, and is a public utility and independent transmission owner in Wisconsin;
(b): Regulated Electric & Gas Utilities — United States: consisting of vertically integrated electrical and gas utilities in the state of Arizona: Tucson Electric Power Company, UNS Electric, Inc. and UNS Gas, Inc., each a subsidiary of UNS Energy Corporation, acquired by us in 2014; together with Central Hudson Gas & Electric Corporation, a regulated transmission and distribution utility located in New York State's Mid-Hudson River Valley, acquired by us in 2013;
(c): Regulated Gas Utility — Canadian: consisting of FortisBC Energy Inc., a regulated gas utility serving the Lower Mainland, Vancouver Island and Whistler regions of British Columbia;

Table of Contents

(d): Regulated Electric Utilities — Canadian: consisting of (i) FortisAlberta, a regulated electric distribution utility serving a substantial portion of southern and central Alberta; (ii) FortisBC Inc., an integrated, regulated electric utility serving the southern interior of British Columbia; (iii) Newfoundland Power Inc., a regulated electric utility that operates throughout the island portion of the Province of Newfoundland and Labrador; (iv) Maritime Electric Company, Limited, a regulated electric utility on Prince Edward Island; and (v) FortisOntario Inc., which provides regulated, integrated electric utility service in Fort Erie, Cornwall, Gananoque and Port Colborne and distributes electricity in the District of Algoma in Ontario;
(e): Regulated Electric Utilities — Caribbean: consisting of (i) an indirect approximate 60% controlling ownership interest in Caribbean Utilities Company, Ltd., an integrated electric utility in Grand Cayman, Cayman Islands, the Class A Ordinary Shares of which are listed on the TSX under the symbol CUP.U; (ii) FortisTCI Limited and Turks and Caicos Utilities Limited, integrated electric utilities on the Turks and Caicos Islands; and (iii) an approximate 33% equity investment in Belize Electricity Limited, an integrated electric utility in Belize;
(f): Non-Regulated — Energy Infrastructure: consisting of (i) our 51% controlling ownership interest in the Waneta expansion hydroelectric generating facility in British Columbia; (ii) the Aitken Creek gas storage facility in British Columbia, acquired by us on April 1, 2016 for US$266 million; and (iii) the 25-MW Mollejon, 7-MW Chalillo and 19-MW Vaca hydroelectric generating facilities in Belize; and
(g): Corporate and Other: captures expense and revenue items not specifically related to any reportable segment and those business operations that are below the required threshold for reporting as separate segments.

SHARE CAPITAL OF FORTIS

Our authorized share capital consists of an unlimited number of Common Shares, an unlimited number of First Preference Shares issuable in series and an unlimited number of Second Preference Shares issuable in series, in each case without nominal or par value. As at November 28, 2016, 399,833,460 Common Shares, 5,000,000 Cumulative Redeemable First Preference Shares, Series F, or the First Preference Shares, Series F, 9,200,000 Cumulative Redeemable Five-Year Fixed Rate Reset First Preference Shares, Series G, or the First Preference Shares, Series G, 7,024,846 Cumulative Redeemable Five-Year Fixed Rate Reset First Preference Shares, Series H, or the First Preference Shares, Series H, 2,975,154 Cumulative Redeemable Floating Rate First Preference Shares, Series I, or the First Preference Shares, Series I, 8,000,000 Cumulative Redeemable First Preference Shares, Series J, or the First Preference Shares, Series J, 10,000,000 Cumulative Redeemable Fixed Rate Reset First Preference Shares, Series K, or the First Preference Shares, Series K, and 24,000,000 Cumulative Redeemable Fixed Rate Reset First Preference Shares, Series M, or the First Preference Shares, Series M, were issued and outstanding. Our Common Shares, First Preference Shares, Series F, First Preference Shares, Series G, First Preference Shares, Series H, First Preference Shares, Series I, First Preference Shares, Series J, First Preference Shares, Series K and First Preference Shares, Series M are listed on the TSX under the symbols "FTS", "FTS.PR.F", "FTS.PR.G", "FTS.PR.H", "FTS.PR.I", "FTS.PR.J", "FTS.PR.K" and "FTS.PR.M", respectively. Our Common Shares are listed on the NYSE under the symbol "FTS".

EARNINGS COVERAGE RATIOS

In accordance with the requirements of the Canadian securities regulatory authorities, the consolidated earnings coverage ratios set out below have been calculated for the 12-month periods ended September 30, 2016 and December 31, 2015. Our interest requirements on all of our outstanding long-term debt amounted to $622 million and $604 million for the 12 months ended September 30, 2016 and the 12 months ended December 31, 2015, respectively. Our dividend requirements on all of our First Preference Shares for the 12 months ended September 30, 2016 and the 12 months ended December 31, 2015, adjusted to a before-tax equivalent, amounted to $97 million using an effective income tax rate of 19.7% and $97 million using an effective income tax rate of 21.0%, respectively. Our earnings before interest and income tax for the 12 months ended September 30, 2016 and the 12 months ended December 31, 2015 were $1,335 million and $1,558 million,

Table of Contents

respectively, which is 1.86 times and 2.22 times, respectively, our aggregate interest and dividend requirements for the periods.

Our earnings coverage ratios, calculated on a pro forma basis after giving effect to the acquisition of ITC, including: (i) the amount of borrowings in connection with the financing of the acquisition of ITC; and (ii) the indebtedness of ITC, on a consolidated basis, on closing of the acquisition, which was $5.9 billion as of September 30, 2016, are calculated as follows: (a) our interest requirements on all of our outstanding long-term debt amounted to $932 million and $703 million for the 12 months ended December 31, 2015 and the nine months ended September 30, 2016, respectively; (b) our dividend requirements on all of our First Preference Shares for the 12 months ended December 31, 2015 and the nine months ended September 30, 2016, adjusted to a before-tax equivalent, amounted to $104 million using an effective income tax rate of 26.2% and $80 million using an effective income tax rate of 26.0%, respectively; and (c) our earnings before interest and income tax for the 12 months ended December 31, 2015 and the nine months ended September 30, 2016 were $2,234 million and $1,608 million, respectively, which is 2.16 times and 2.05 times, respectively, our aggregate interest and dividend requirements for the periods after giving effect to the acquisition of ITC and the financing thereof as described above.

These earnings coverage ratios do not purport to be indicative of earnings coverage ratios for any future periods. The earnings coverage ratios and dividend and interest requirements do not give effect to the issuance of any Securities that may be issued pursuant to this Prospectus and any Prospectus Supplement, since the aggregate principal amounts and the terms of such Securities are not currently known. If we offer First Preference Shares, Second Preference Shares or Debt Securities having a term to maturity in excess of one year under this Prospectus, the applicable Prospectus Supplement will include earnings coverage ratios giving effect to the issuance of such Securities.

DIVIDEND POLICY

Dividends on the Common Shares are declared at the discretion of our board of directors, or the Board of Directors. We declared and paid cumulative cash dividends on our Common Shares of $1.395 in 2015, $1.28 in 2014 and $1.24 in 2013. On December 16, 2015, our Board of Directors declared a first quarter dividend of $0.375 per Common Share, which was paid on March 1, 2016 to holders of record on February 17, 2016. On February 17, 2016, our Board of Directors declared a second quarter dividend of $0.375 per Common Share, which was paid on June 1, 2016 to holders of record on May 18, 2016. On July 28, 2016, our Board of Directors declared a third quarter dividend of $0.375 per Common Share, which was paid on September 1, 2016 to holders of record on August 19, 2016. On September 27, 2016, our Board of Directors declared a fourth quarter dividend of $0.40 per Common Share, which will be paid on December 1, 2016 to holders of record on November 18, 2016. We have increased our annual Common Share dividend payment for 43 consecutive years.

During the third quarter of 2016, we provided dividend guidance targeting average annual dividend growth of 6% through 2021. This guidance takes into account many factors, including the successful integration of ITC, the expectation of reasonable outcomes for regulatory proceedings at our utilities, the successful execution of our $13 billion five-year capital plan and management's continued confidence in the strength of our diversified portfolio of assets and record of operational excellence.

Regular quarterly dividends at the prescribed annual rate have been paid on all of the First Preference Shares, Series F; First Preference Shares, Series G; First Preference Shares, Series H; First Preference Shares, Series I; First Preference Shares, Series J; First Preference Shares, Series K; and First Preference Shares, Series M, or the Outstanding First Preference Shares, respectively. Our Board of Directors declared a first quarter dividend on the Outstanding First Preference Shares on December 16, 2015, in each case in accordance with the applicable prescribed annual rate or floating rate, as the case may be, which was paid on March 1, 2016 to holders of record on February 17, 2016. On February 17, 2016, our Board of Directors declared a second quarter dividend on the Outstanding First Preference Shares, in accordance with the applicable prescribed annual rate or floating rate, as the case may be, in each case which was paid on June 1, 2016 to holders of record on May 18, 2016. On July 28, 2016 our Board of Directors declared a third quarter dividend on the Outstanding First Preference Shares, in accordance with the applicable prescribed annual rate or floating rate, as the case may be, in each case which was paid on September 1, 2016 to holders of record on August 19, 2016. On

Table of Contents

September 27, 2016 our Board of Directors declared a fourth quarter dividend on the Outstanding First Preference Shares, in accordance with the applicable prescribed annual rate or floating rate, as the case may be, in each case to be paid on December 1, 2016 to holders of record on November 18, 2016.

DESCRIPTION OF SECURITIES OFFERED

Common Shares

Common Shares may be offered separately or together with First Preference Shares, Second Preference Shares, Subscription Receipts or Debt Securities under this Prospectus. Common Shares may also be issuable on conversion or exchange of certain Debt Securities and Subscription Receipts qualified for issuance under this Prospectus. Each Common Share offered hereunder will have the terms described below.

Dividends

Dividends on Common Shares are declared at the discretion of our Board of Directors. Holders of Common Shares are entitled to dividends on apro rata basis if, as and when declared by our Board of Directors. Subject to the rights of the holders of the First Preference Shares and Second Preference Shares and any of our other classes of shares entitled to receive dividends in priority to or rateably with the holders of the Common Shares, our Board of Directors may declare dividends on the Common Shares to the exclusion of any of our other classes of shares.

Liquidation, Dissolution or Winding-Up

On our liquidation, dissolution or winding-up, holders of Common Shares are entitled to participate rateably in any distribution of our assets, subject to the rights of holders of First Preference Shares and Second Preference Shares and any of our other classes of shares entitled to receive our assets on such a distribution in priority to or rateably with the holders of the Common Shares.

Voting Rights

Holders of the Common Shares are entitled to receive notice of and to attend all annual and special meetings of our shareholders, other than separate meetings of holders of any other class or series of shares, and to one vote in respect of each Common Share held at such meetings.

First Preference Shares

The following is a summary of the material rights, privileges, conditions and restrictions attached to the First Preference Shares as a class. The specific terms of the First Preference Shares, including the currency in which First Preference Shares may be purchased and redeemed and the currency in which any dividend is payable, if other than Canadian dollars, and the extent to which the general terms described in this section apply to those First Preference Shares, will be set forth in the applicable Prospectus Supplement. One or more series of First Preference Shares may be sold separately or together with Common Shares, Second Preference Shares, Subscription Receipts or Debt Securities under this Prospectus.

Issuance in Series

Our Board of Directors may from time to time issue First Preference Shares in one or more series. Prior to issuing shares in a series, our Board of Directors is required to fix the number of shares in the series and determine the designation, rights, privileges, restrictions and conditions attaching to that series of First Preference Shares.

Priority

The shares of each series of First Preference Shares rank on a parity with the First Preference Shares of every other series and in priority to all of our other shares, including the Second Preference Shares, as to the payment of dividends, return of capital and the distribution of our assets in the event of a liquidation, dissolution or winding-up, whether voluntary or involuntary, or any other distribution of our assets among our shareholders

Table of Contents

for the purpose of winding-up our affairs. Each series of First Preference Shares participates rateably with every other series of First Preference Shares in respect of accumulated cumulative dividends and returns of capital if any amount of cumulative dividends, whether or not declared, or amount payable on the return of capital in respect of a series of First Preference Shares, is not paid in full.

Voting

The holders of the First Preference Shares are not entitled to any voting rights as a class except to the extent that voting rights may from time to time be attached to any series of First Preference Shares, and except as provided by law or as described below under "— Modification". At any meeting of the holders of First Preference Shares, each holder shall have one vote in respect of each First Preference Share held.

Redemption

Subject to the provisions of theCorporations Act (Newfoundland and Labrador) and any provisions relating to any particular series, we, upon giving proper notice, may redeem out of capital or otherwise at any time, or from time to time, the whole or any part of the then outstanding First Preference Shares of any one or more series on payment for each such First Preference Share of such price or prices as may be applicable to such series. Subject to the foregoing, if only a part of the then outstanding First Preference Shares of any particular series is at any time redeemed, the shares to be redeemed will be selected by lot in such manner as our Board of Directors or the transfer agent for the First Preference Shares, if any, decide, or if our Board of Directors so determine, may be redeemedpro rata disregarding fractions.

Modification

The class provisions attached to the First Preference Shares may only be amended with the prior approval of the holders of the First Preference Shares in addition to any other approvals required by theCorporations Act (Newfoundland and Labrador) or any other statutory provisions of like or similar effect in force from time to time. The approval of the holders of the First Preference Shares with respect to any and all matters may be given by at least two-thirds of the votes cast at a meeting of the holders of the First Preference Shares duly called for that purpose.

Second Preference Shares

The rights, privileges, conditions and restrictions attaching to the Second Preference Shares are substantially identical to those attaching to the First Preference Shares, except that the Second Preference Shares are junior to the First Preference Shares with respect to the payment of dividends, repayment of capital and the distribution of our assets in the event of a liquidation, dissolution or winding up.

The specific terms of the Second Preference Shares, including the currency in which Second Preference Shares may be purchased and redeemed and the currency in which any dividend is payable, if other than Canadian dollars, and the extent to which the general terms described in this Prospectus apply to those Second Preference Shares, will be set forth in the applicable Prospectus Supplement. One or more series of Second Preference Shares may be sold separately or together with Common Shares, First Preference Shares, Subscription Receipts or Debt Securities under this Prospectus.

Subscription Receipts

Subscription Receipts may be offered separately or together with Common Shares, First Preference Shares, Second Preference Shares or Debt Securities, as the case may be. Subscription Receipts will be issued under a subscription receipt agreement, or the Subscription Receipt Agreement, that will be entered into between us and the escrow agent, or the Escrow Agent, at the time of issuance of the Subscription Receipts. Each Escrow Agent will be a financial institution authorized to carry on business as a trustee. If underwriters or agents are used in the sale of any Subscription Receipts, one or more of such underwriters or agents may also be a party to the Subscription Receipt Agreement governing the Subscription Receipts sold to or through such underwriter or agent.

Table of Contents

The Subscription Receipt Agreement will provide each initial purchaser of Subscription Receipts with a non-assignable contractual right of rescission following the issuance of any Common Shares, First Preference Shares, Second Preference Shares or Debt Securities, as applicable, to such purchaser upon the exchange of the Subscription Receipts if this Prospectus, the Prospectus Supplement under which the Subscription Receipts are offered, or any amendment hereto or thereto contains a misrepresentation, as such term is defined in theSecurities Act (Ontario). This contractual right of rescission will entitle such initial purchaser to receive the amount paid for the Subscription Receipts upon surrender of the Securities issued in exchange therefor, provided that such remedy for rescission is exercised in the time stipulated in the Subscription Receipt Agreement. This right of rescission will not extend to any holders of Subscription Receipts who acquire such Subscription Receipts from an initial purchaser on the open market or otherwise.

The applicable Prospectus Supplement will include details of the Subscription Receipt Agreement covering the Subscription Receipts being offered. The specific terms of the Subscription Receipts, and the extent to which the general terms described in this section apply to those Subscription Receipts, will be set forth in the applicable Prospectus Supplement. A copy of the Subscription Receipt Agreement will be filed by us with securities regulatory authorities after it has been entered into by us and will be available on our SEDAR profile atwww.sedar.com.

This section describes the general terms that will apply to any Subscription Receipts being offered. The terms and provisions of any Subscription Receipts offered under a Prospectus Supplement may differ from the terms described below, and may not be subject to or contain any or all of such terms. The particular terms of each issue of Subscription Receipts that will be described in the related Prospectus Supplement will include, where applicable:

(a): the number of Subscription Receipts;
(b): the price at which the Subscription Receipts will be offered;
(c): conditions, or the Release Conditions, for the exchange of Subscription Receipts into Common Shares, First Preference Shares, Second Preference Shares or Debt Securities, as the case may be, and the consequences of such conditions not being satisfied;
(d): the procedures for the exchange of the Subscription Receipts into Common Shares, First Preference Shares, Second Preference Shares or Debt Securities;
(e): the number of Common Shares, First Preference Shares, Second Preference Shares or Debt Securities to be exchanged for each Subscription Receipt;
(f): the aggregate principal amount, currency or currencies, denominations and terms of the series of Common Shares, First Preference Shares, Second Preference Shares or Debt Securities that may be exchanged upon exercise of each Subscription Receipt;
(g): the designation and terms of any other Securities with which the Subscription Receipts will be offered, if any, and the number of Subscription Receipts that will be offered with each Security;
(h): the dates or periods during which the Subscription Receipts may be exchanged into Common Shares, First Preference Shares, Second Preference Shares or Debt Securities;
(i): the identity of the Escrow Agent;
(j): the terms and conditions under which the Escrow Agent will hold all or a portion of the gross proceeds from the sale of such Subscription Receipts, together with interest and income earned thereon, or collectively, the Escrowed Funds, pending satisfaction of the Release Conditions;
(k): the terms and conditions under which the Escrow Agent will release all or a portion of the Escrowed Funds to us upon satisfaction of the Release Conditions and if the Subscription Receipts are sold to or through underwriters or agents, the terms and conditions under which the Escrow Agent will release a portion of the Escrowed Funds to such underwriters or agents in payment of all or a portion of their fees or commissions in connection with the sale of the Subscription Receipts;

Table of Contents

(l): procedures for the payment by the Escrow Agent to holders of such Subscription Receipts of an amount equal to all or a portion of the subscription price of their Subscription Receipts, plus any additional amounts provided for in the Subscription Receipt Agreement, if the Release Conditions are not satisfied;
(m): any contractual right of rescission to be granted to initial purchasers of such Subscription Receipts in the event that this Prospectus, the Prospectus Supplement under which Subscription Receipts are issued or any amendment hereto or thereto contains a misrepresentation;
(n): material U.S. and Canadian federal income tax consequences of owning the Subscription Receipts; and
(o): any other material terms and conditions of the Subscription Receipts.

Prior to the exchange of their Subscription Receipts, holders of Subscription Receipts will not have any of the rights of holders of the securities to be received on the exchange of the Subscription Receipts.

Escrow

The Subscription Receipt Agreement will provide that the Escrowed Funds will be held in escrow by the Escrow Agent, and such Escrowed Funds will be released to us (and, if the Subscription Receipts are sold to or through underwriters or agents, a portion of the Escrowed Funds may be released to such underwriters or agents in payment of all or a portion of their fees in connection with the sale of the Subscription Receipts) at the time and under the terms specified by the Subscription Receipt Agreement. If the Release Conditions are not satisfied, holders of Subscription Receipts will receive payment of an amount equal to all or a portion of the subscription price for their Subscription Receipts, plus any additional amounts provided for in the Subscription Receipt Agreement, in accordance with the terms of the Subscription Receipt Agreement.

Modifications

The Subscription Receipt Agreement will specify the terms upon which modifications and alterations to the Subscription Receipts issued thereunder may be made by way of a resolution of holders of Subscription Receipts at a meeting of such holders or by way of consent in writing from such holders. The number of holders of Subscription Receipts required to pass such a resolution or execute such a written consent will be specified in the Subscription Receipt Agreement. The Subscription Receipt Agreement will also specify that we may amend the Subscription Receipt Agreement and the Subscription Receipts, without the consent of the holders of the Subscription Receipts, to cure any ambiguity, to cure, correct or supplement any defective or inconsistent provision, or in any other manner that will not materially and adversely affect the interests of the holder of outstanding Subscription Receipts or as otherwise specified in the Subscription Receipt Agreement.

Debt Securities

Debt Securities, which will be our direct senior or subordinated obligations, may be offered separately or together with Common Shares, First Preference Shares, Second Preference Shares or Subscription Receipts under this Prospectus, or on conversion or exchange of any such Securities. The particular terms and provisions of a series of Debt Securities offered pursuant to an accompanying Prospectus Supplement, and the extent to which the general terms and provisions described below may apply to such Debt Securities, will be described in the applicable Prospectus Supplement.

Debt Securities may be issued under a trust indenture dated as of July 2, 2009, between us and Computershare Trust Company of Canada, or the Canadian Indenture, or under a trust indenture dated as of October 4, 2016 between us, The Bank of New York Mellon, as the U.S. trustee, and BNY Trust Company of Canada, as the Canadian co-trustee, or the U.S. Indenture, a copy of each of which has been filed on our SEDAR profile atwww.sedar.com, in each case as supplemented from time to time. Debt Securities issued under the Canadian Indenture will not be offered or sold to persons in the U.S. pursuant to this Prospectus. Debt Securities may also be issued under new indentures between us and a trustee or trustees as will be described in a Prospectus Supplement for such Debt Securities, or collectively, with the Canadian Indenture and the U.S. Indenture, the Indentures. A copy of any Indenture or supplement thereto entered into by us will be filed with securities regulatory authorities and will be available on our SEDAR profile atwww.sedar.com.

Table of Contents

We conduct our business primarily through our subsidiaries. Accordingly, our ability to meet our obligations under the Debt Securities is dependent primarily on the earnings and cash flows of those subsidiaries and the ability of those subsidiaries to pay dividends or to advance or repay funds to us. Our subsidiaries are separate legal entities and have no independent obligation to pay dividends to us. Prior to paying dividends to us, the subsidiaries have financial obligations that must be satisfied, including among others, their operating expenses and obligations to creditors. Furthermore, our regulated utilities are required by regulation to maintain a minimum equity-to-total capital ratio that may restrict their ability to pay dividends to us or may require that we contribute capital. The future enactment of laws or regulations may prohibit or further restrict the ability of our subsidiaries to pay upstream dividends or to repay intercorporate indebtedness. In addition, the rights that we and our creditors would have to participate in the assets of any such subsidiary upon the subsidiary's liquidation or recapitalization will be subject to the prior claims of the subsidiary's creditors. Certain of our subsidiaries have incurred substantial amounts of debt in the operations and expansion of their businesses, and we anticipate that certain of our subsidiaries will continue to do so in the future.

Holders of Debt Securities will generally have a junior position to claims of creditors of our subsidiaries, including trade creditors, debt holders, secured creditors, taxing authorities, guarantee holders and any holders of preference or preferred shares. In addition to trade debt, certain of our operating subsidiaries have ongoing corporate debt programs used to finance their business activities. The Debt Securities will be effectively subordinated to any of our existing and future secured obligations to the extent of the value of the collateral securing such obligations. The Debt Securities will be structurally subordinated to all liabilities and any preference or preferred shares of our subsidiaries.

As of November 28, 2016, on a consolidated basis (including securities due within one year), we and our operating subsidiaries had approximately $22.7 billion of outstanding debt, of which approximately $16.4 billion was subsidiary debt. Unless otherwise specified in a Prospectus Supplement, the Canadian Indenture and the U.S. Indenture do not limit, and future Indentures will not limit, the amount of indebtedness or preference or preferred shares issuable by our subsidiaries.

The following description of the Debt Securities is only a summary and is not intended to be comprehensive. For additional information you should refer to the Indenture under which such Debt Securities are issued.

General

The Indentures will not limit the amount of Debt Securities that we may issue thereunder. We may issue Debt Securities from time to time under an Indenture in one or more series by entering into supplemental indentures or by our Board of Directors or a duly authorized committee authorizing the issuance. The Debt Securities of a series need not be issued at the same time, bear interest at the same rate or mature on the same date.

The Prospectus Supplement for a particular series of Debt Securities will disclose the specific terms of such Debt Securities, including the price or prices at which the Debt Securities to be offered will be issued. Those terms may include some or all of the following:

(a): the title of the series;
(b): the total principal amount of the Debt Securities of the series;

Table of Contents

(c): the date or dates on which principal is payable or the method for determining the date or dates, and any right that we have to change the date on which principal is payable;
(d): the interest rate or rates, if any, or the method for determining the rate or rates, and the date or dates from which interest will accrue;
(e): any interest payment dates and the regular record date for the interest payable on each interest payment date, if any;
(f): whether we may extend the interest payment periods and, if so, the terms of the extension;
(g): the place or places where payments will be made;
(h): whether we have the option to redeem the Debt Securities and, if so, the terms of such redemption option;
(i): any obligation that we have to redeem the Debt Securities through a sinking fund or to purchase the Debt Securities through a purchase fund or at the option of the holder;
(j): any conversion or exchange right granted to holders, the terms and conditions thereof and the number and designation of the securities to be received by holders on any such conversion or exchange;
(k): the currency in which the Debt Securities may be purchased and in which the principal and any interest is payable;
(l): if payments may be made, at our election or at the holder's election, in a currency other than that in which the Debt Securities are stated to be payable, then the currency in which those payments may be made, the terms and conditions of the election and the manner of determining those amounts;
(m): the portion of the principal payable upon acceleration of maturity, if other than the entire principal;
(n): whether the Debt Securities will be issuable as global securities and, if so, the securities depositary;
(o): the events of default or covenants with respect to the Debt Securities;
(p): any index or formula used for determining principal, premium or interest;
(q): the terms of the subordination of any series of subordinated debt;
(r): if the principal payable on the maturity date will not be determinable on one or more dates prior to the maturity date, the amount which will be deemed to be such principal amount or the manner of determining it;
(s): the person to whom any interest shall be payable if other than the person in whose name the Debt Security is registered on the regular record date for such interest payment; and
(t): any other terms.

The Debt Securities offered pursuant to this Prospectus and any Prospectus Supplement may be represented by instalment receipts, the particular terms and provisions of which will be described in the applicable Prospectus Supplement and set out in an instalment receipt and pledge agreement. Any such instalment receipt will evidence, among other things, (a) the fact that a first instalment payment has been made in respect of the Debt Securities represented thereby and (b) the beneficial ownership of the Debt Securities represented by the instalment receipt, subject to a pledge of such Debt Securities securing the obligation to pay the balance outstanding under such Debt Securities on or prior to a certain date. A copy of any such instalment receipt and pledge agreement will be filed by us with securities regulatory authorities after it has been entered into and will be available on our SEDAR profile atwww.sedar.com.

Table of Contents

CHANGES IN SHARE AND LOAN CAPITAL STRUCTURE

The following describes the changes in our share and loan capital structure since September 30, 2016:

(a)

On October 14, 2016 we issued 114,363,774 Common Shares to former holders of ITC common stock as partial consideration for the acquisition of ITC.

(b)

During the period from October 1, 2016 up to and including November 28, 2016, our consolidated long-term debt, capital lease and finance obligations, including current portions and committed credit facility borrowings classified as long-term debt increased by approximately $9.8 billion, principally due to:

(i): the issuance on October 4, 2016 of an aggregate principal amount of US$2 billion of Exchangeable Notes (as defined below) in connection with the financing of the acquisition of ITC;
(ii): the drawdown on October 13, 2016 of $535 million (approximately US$404 million) from our non-revolving term senior unsecured equity bridge facility with The Bank of Nova Scotia, repayable in full 364 days following its advance, in connection with the financing of the acquisition of ITC;
(iii): approximately US$4.6 billion (at fair value) of consolidated long-term debt of ITC and its subsidiaries outstanding on October 14, 2016, the date of closing of the acquisition of ITC by Fortis;
(iv): the issuance of a shareholder note in the principal amount of US$199 million by a subsidiary of Fortis in favour of Eiffel Investment Pte Ltd, an affiliate of GIC, in connection with the financing of the acquisition of ITC; and
(v): changes in foreign exchange rates over the period.

Table of Contents

PRIOR SALES

We have not sold or issued any First Preference Shares, Second Preference Shares or Subscription Receipts or securities convertible into First Preference Shares, Second Preference Shares or Debt Securities during the 12 months prior to the date hereof. The following table summarizes our issuances of Common Shares and securities convertible into Common Shares or exchangeable for Debt Securities during the 12 months prior to the date of this Prospectus:

Date	Security

November 2015	Common — Exercise of Stock Options⁽¹⁾	$29.26	45,288
November 2015	Common — Conversion of Convertible Debentures⁽²⁾	$30.72	2,701
December 1, 2015	Common — DRIP⁽³⁾	$36.13	1,214,623
December 1, 2015	Common — ESPP⁽⁴⁾	$36.84	70,242
December 1, 2015	Common — CSPP⁽⁵⁾	$36.87	7,855
December 2015	Common — Exercise of Stock Options⁽¹⁾	$25.94	22,101
December 2015	Common — Conversion of Convertible Debentures⁽²⁾	$30.72	1,627
January 2016	Common — Exercise of Stock Options⁽¹⁾	$22.84	38,061
February 2016	Common — Exercise of Stock Options⁽¹⁾	$23.84	340,002
March 1, 2016	Common — DRIP⁽³⁾	$37.31	778,491
March 1, 2016	Common — ESPP⁽⁴⁾	$38.25	140,536
March 1, 2016	Common — CSPP⁽⁵⁾	$38.05	7,300
March 2016	Common — Exercise of Stock Options⁽¹⁾	$23.77	181,861
March 2016	Common — Conversion of Convertible Debentures⁽²⁾	$30.72	1,398
April 2016	Common — Exercise of Stock Options⁽¹⁾	$33.04	48,587
April 2016	Common — Conversion of Convertible Debentures⁽²⁾	$30.72	325
May 2016	Common — Exercise of Stock Options⁽¹⁾	$30.11	19,660
June 1, 2016	Common — DRIP⁽³⁾	$40.21	912,982
June 1, 2016	Common — ESPP⁽⁴⁾	$41.02	80,013
June 1, 2016	Common — CSPP⁽⁵⁾	$41.02	7,306
June 2016	Common — Exercise of Stock Options⁽¹⁾	$28.30	67,424
June 2016	Common — Conversion of Convertible Debentures⁽²⁾	$30.72	813
July 2016	Common — Exercise of Stock Options⁽¹⁾	$30.61	280,627
July 2016	Common — Conversion of Convertible Debentures⁽²⁾	$30.72	1,627
August 2016	Common — Exercise of Stock Options⁽¹⁾	$32.95	12,292
August 2016	Common — Conversion of Convertible Debentures⁽²⁾	$30.72	4,979
September 1, 2016	Common — DRIP⁽³⁾	$41.30	908,685
September 1, 2016	Common — ESPP⁽⁴⁾	$41.95	67,451
September 1, 2016	Common — CSPP⁽⁵⁾	$42.14	5,996
September 2016	Common — Conversion of Convertible Debentures⁽²⁾	$30.72	651
October 4, 2016	Debt securities⁽⁶⁾	US$2,000	1,000,000
October 14, 2016	Common — Acquisition of ITC⁽⁷⁾	$40.96	114,363,774

(1): Issued on the exercise of options granted pursuant to our 2006 and 2012 Stock Option Plans.
(2): Issued upon the conversion of the convertible debentures issued by us on January 9, 2014 in connection with the financing of the acquisition of UNS Energy.
(3): Issued pursuant to our Dividend Reinvestment Plan, or DRIP.
(4): Issued pursuant to our Employee Share Purchase Plan, or ESPP.
(5): Issued pursuant to our Consumer Share Purchase Plan, or CSPP.
(6): Exchangeable Notes issued on October 4, 2016 in connection with the financing of the acquisition of ITC.
(7): Issued to former holders of ITC common stock as partial consideration for the acquisition of ITC.

Table of Contents

TRADING PRICES AND VOLUMES

The following tables set forth, for the periods indicated, the reported high and low daily trading prices and the aggregate volume of trading of our Common Shares on the TSX and NYSE and of our Outstanding First Preference Shares on the TSX.

	Trading of Common Shares						Trading of Common Shares

	TSX						NYSE
	High		Low		Volume		High		Low		Volume
	($)		($)		(#)		(US$)		(US$)		(#)
2015
November		38.60		36.35		12,504,209		—		—		—
December		38.26		35.51		15,464,056		—		—		—
2016
January		40.71		35.79		15,310,648		—		—		—
February		41.58		35.53		42,973,318		—		—		—
March		41.08		37.74		24,278,066		—		—		—
April		41.09		38.52		16,625,820		—		—		—
May		41.48		39.50		19,329,553		—		—		—
June		43.91		40.78		20,791,983		—		—		—
July		44.87		42.79		16,617,319		—		—		—
August		43.75		40.99		16,936,055		—		—		—
September		42.83		40.32		18,057,520		—		—		—
October⁽¹⁾		44.22		40.13		55,424,615		33.25		31.03		9,326,578
November 1 to 28		44.27		39.58		25,023,308		33.10		29.14		6,834,455

(1): The Common Shares commenced trading on the NYSE on October 14, 2016.

	Trading of First Preference Shares, Series F						Trading of First Preference Shares, Series G

	TSX						TSX
	High		Low		Volume		High		Low		Volume
	($)		($)		(#)		($)		($)		(#)
2015
November		23.55		21.95		128,647		19.96		17.78		280,941
December		23.71		21.65		87,471		18.49		15.57		374,203
2016
January		23.39		20.70		71,898		18.40		13.67		183,048
February		22.50		21.25		72,699		16.40		13.80		128,071
March		22.75		21.41		68,513		16.35		14.15		88,313
April		23.65		22.43		64,624		17.80		16.03		117,620
May		23.98		22.99		35,996		17.47		15.98		74,399
June		24.10		23.01		42,356		17.47		16.04		367,192
July		25.12		23.51		119,301		18.20		16.63		90,198
August		25.40		24.68		44,020		19.14		17.76		113,488
September		24.95		24.46		62,489		18.25		17.32		163,254
October		24.80		24.05		53,777		18.67		17.37		239,666
November 1 to 28		24.70		22.82		81,501		18.68		17.30		292,566

Table of Contents

	Trading of First Preference Shares, Series H						Trading of First Preference Shares, Series I

	TSX						TSX
	High		Low		Volume		High		Low		Volume
	($)		($)		(#)		($)		($)		(#)
2015
November		15.70		13.95		110,962		13.75		12.00		75,755
December		14.81		12.75		145,156		13.00		10.92		101,208
2016
January		14.75		11.62		114,195		12.56		10.35		38,209
February		13.24		10.72		245,359		10.74		8.90		45,475
March		12.90		10.80		262,353		10.85		9.17		36,170
April		13.88		12.81		155,271		12.00		10.50		38,797
May		13.91		12.51		323,457		12.04		11.25		46,678
June		14.41		13.15		70,281		12.16		11.62		72,197
July		14.38		13.65		42,089		12.41		12.00		20,709
August		14.54		13.54		89,971		12.85		11.88		32,400
September		14.16		13.25		280,831		12.13		11.58		52,530
October		14.34		13.86		104,354		13.04		12.05		89,636
November 1 to 28		14.44		13.32		207,760		12.49		11.99		194,906

	Trading of First Preference Shares, Series J						Trading of First Preference Shares, Series K

	TSX						TSX
	High		Low		Volume		High		Low		Volume
	($)		($)		(#)		($)		($)		(#)
2015
November		22.85		21.23		112,115		20.49		18.52		404,180
December		23.00		20.80		76,388		19.39		16.56		314,369
2016
January		22.66		19.15		109,984		19.02		14.77		176,736
February		21.84		20.45		84,608		16.50		14.35		111,411
March		21.88		20.82		213,627		16.66		14.59		91,313
April		22.76		21.70		62,788		17.95		16.25		77,469
May		23.17		22.22		63,674		17.56		16.59		139,343
June		23.52		22.27		59,206		17.82		16.60		148,499
July		24.22		22.80		347,487		18.25		16.90		259,099
August		24.49		23.70		100,536		19.19		17.91		112,893
September		24.27		23.61		236,018		18.26		17.65		125,371
October		24.27		23.60		393,068		18.32		16.42		283,093
November 1 to 28		24.08		22.15		103,743		18.57		17.11		246,395

Table of Contents

	Trading of First Preference Shares, Series M

	TSX
	High		Low		Volume
	($)		($)		(#)
2015
November		22.83		19.85		311,587
December		21.19		17.90		792,543
2016
January		20.90		15.94		304,778
February		18.48		15.30		586,706
March		18.56		15.97		564,271
April		20.36		18.14		498,847
May		19.99		18.00		386,165
June		19.98		18.06		300,512
July		19.98		18.57		186,597
August		20.87		19.71		487,473
September		20.60		19.42		276,502
October		19.98		19.09		291,230
November 1 to 28		20.68		19.15		573,983

USE OF PROCEEDS

We intend to use the net proceeds from the sale of Securities to repay indebtedness, to directly or indirectly finance future growth opportunities and/or for general corporate purposes. Specific information about the use of net proceeds of any offering of Securities under this Prospectus will be set forth in the applicable Prospectus Supplement. We may invest funds which we do not immediately use. Such investments may include short-term marketable investment grade securities denominated in Canadian dollars, U.S. dollars or other currencies. We may, from time to time, issue securities other than pursuant to this Prospectus.

PLAN OF DISTRIBUTION

We and any Selling Securityholder may sell the Securities, separately or together, to or through one or more underwriters or dealers, purchasing as principals for public offering and sale by them, and may also sell Securities to one or more other purchasers directly or through agents. Securities sold to the public pursuant to this Prospectus may be offered and sold exclusively in Canada or the U.S., or in both jurisdictions. The Prospectus Supplement relating to an offering of Securities will indicate the jurisdiction or jurisdictions in which such offering is being made to the public. Each Prospectus Supplement will set out the terms of the offering, including the name or names of any underwriters, dealers or agents, the purchase price or prices of the Securities (or the manner of determination thereof if offered on a non-fixed price basis), and the proceeds to us or the applicable Selling Securityholder from the sale of the Securities. Only underwriters, dealers or agents so named in the Prospectus Supplement are deemed to be underwriters, dealers or agents, as the case may be, in connection with the Securities offered thereby.

The Securities may be sold, from time to time in one or more transactions at a fixed price or prices which may be changed or at market prices prevailing at the time of sale, at prices related to such prevailing market prices or at negotiated prices. The prices at which the Securities may be offered may vary between purchasers and during the period of distribution. If, in connection with the offering of Securities at a fixed price or prices, the underwriters have made abona fide effort to sell all of the Securities at the initial offering price fixed in the applicable Prospectus Supplement, the public offering price may be decreased and thereafter further changed, from time to time, to an amount not greater than the initial public offering price fixed in such Prospectus Supplement, in which case the compensation realized by the underwriters, dealers or agents will be decreased by the amount that the aggregate price paid by purchasers for the Securities is less than the gross proceeds paid by the underwriters, dealers or agents to us or the applicable Selling Securityholder.

Table of Contents

If underwriters or dealers purchase Securities as principals, the Securities will be acquired by the underwriters or dealers 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 obligations of the underwriters or dealers to purchase those Securities will be subject to certain conditions precedent, and the underwriters or dealers will be obligated to purchase all the Securities offered by the Prospectus Supplement if any of such Securities are purchased. Any public offering price and any discounts or concessions allowed or re-allowed or paid may be changed from time to time.

The Securities may also be sold directly by us or any Selling Securityholder in accordance with applicable securities laws at prices and upon terms agreed to by the purchaser and us or the Selling Securityholder, as applicable, or through agents designated by us or the Selling Securityholder, as applicable, from time to time. Any agent involved in the offering and sale of Securities pursuant to a particular Prospectus Supplement will be named, and any commissions payable by us or the Selling Securityholder, as applicable, to that agent will be set forth, in such Prospectus Supplement. Unless otherwise indicated in the Prospectus Supplement, any agent would be acting on a best efforts basis for the period of its appointment.

In connection with the sale of the Securities, underwriters, dealers or agents may receive compensation from us or the Selling Securityholder, as applicable, in the form of commissions, concessions and discounts. Any such commissions may be paid out of our or the Selling Securityholder's general funds, as applicable, or the proceeds of the sale of Securities. Underwriters, dealers and agents who participate in the distribution of the Securities may be entitled under agreement to be entered into with the us or the Selling Securityholder, as applicable, to indemnification by us or the Selling Securityholder, as applicable, against certain liabilities, including liabilities under Canadian securities legislation, or to contribution with respect to payments which such underwriters, dealers or agents may be required to make in respect thereof. Such underwriters, dealers and agents may engage in transactions with, or perform services for, us in the ordinary course of business.

In connection with any offering of Securities, the applicable Prospectus Supplement will set forth any intention by the underwriters, dealers or agents to offer, allot or effect transactions which stabilize or maintain the market price of the Securities offered at a level above that which might otherwise prevail in the open market. Such transactions, if commenced, may be interrupted or discontinued at any time.

We may also issue Debt Securities under a Prospectus Supplement in exchange for an equal principal amount of our US$500 million 2.100% Notes due 2021 and our US$1,500 million 3.055% Notes due 2026, or collectively, the Exchangeable Notes, issued on October 4, 2016 in a transaction that was exempt from registration under the Securities Act. The Exchangeable Notes were issued by us to initial purchasers, or the Initial Purchasers, and sold by the Initial Purchasers to qualified institutional buyers in the U.S. in reliance on Rule 144A and to non-U.S. persons outside the U.S. in reliance on Regulation S. In connection with the issuance of the Exchangeable Notes, we entered into an exchange and registration rights agreement with the Initial Purchasers dated October 4, 2016, a copy of which is available on our SEDAR profile atwww.sedar.com.

SELLING SECURITYHOLDERS

This Prospectus may also, from time to time, relate to the offering of Securities by way of a secondary offering by certain Selling Securityholders. The terms under which the Securities may be offered by Selling Securityholders will be described in the applicable Prospectus Supplement. The Prospectus Supplement for or including any offering of Securities by Selling Securityholders will include, without limitation, where applicable: (a) the names of the Selling Securityholders; (b) the number and type of Securities owned, controlled or directed by each of the Selling Securityholders; (c) the number of Securities being distributed for the account of each Selling Securityholder; (d) the number of Securities to be owned, controlled or directed by the Selling Securityholders after the distribution and the percentage that number or amount represents out of the total number of outstanding Securities of the relevant class; (e) whether the Securities are owned by the Selling Securityholders, both of record and beneficially, of record only or beneficially only; (f) if the Selling Securityholder purchased any of the Securities held by it in the 24 months preceding the date of the Prospectus Supplement, the date or dates on which the Selling Securityholders acquired the Securities; and (g) if the Selling Securityholder acquired the Securities held by it in the 12 months preceding the date of the Prospectus Supplement, the cost thereof to the Selling Securityholder in the aggregate and on a per security basis.

Table of Contents

CERTAIN INCOME TAX CONSIDERATIONS

The applicable Prospectus Supplement will describe certain material Canadian federal income tax consequences to an investor of the acquisition, ownership and disposition of any Securities offered thereunder. The applicable Prospectus Supplement may also describe certain U.S. federal income tax considerations generally applicable to the acquisition, ownership and disposition of any Securities offered thereunder by an investor who is a U.S. person.

RISK FACTORS

An investment in the Securities involves certain risks. A prospective purchaser of Securities should carefully consider the risk factors described under:

(a): the heading "Business Risk Management" found on pages 43 to 59 of the Annual MD&A;
(b): note 32 "Financial Risk Management" found on pages 69 to 73 of the Annual Financial Statements;
(c): the heading "Business Risk Management" found on page 28 of the Interim MD&A;
(d): note 19 "Financial Risk Management" found on pages F-27 to F-31 of the Interim Financial Statements;
(e): the heading "Risk Factors" found on pages D-14 to D-22 of the Management Information Circular, which include certain risks that relate to the business and operations of ITC;
(f): "Schedule G — Risk Factors" to the Management Information Circular;
(g): "Schedule A — Risk Factors" to the ITC Business Acquisition Report; and
(h): the heading "Item 1A. Risk Factors" found on pages 48 to 51 of "Schedule B — ITC Interim Financial Statements and MD&A" to the ITC Business Acquisition Report, which include certain risks that relate to the business and operations of ITC,

each of which is incorporated by reference herein. In addition, prospective purchasers of Securities should carefully consider, in light of their own financial circumstances, the risk factors set out below, as well as the other information contained in this Prospectus (including the documents incorporated by reference herein) and in all subsequently filed documents incorporated by reference and those described in a Prospectus Supplement relating to a specific offering of Securities, before making an investment decision.

As a foreign private issuer, we are permitted to follow certain home country corporate governance practices instead of otherwise applicable SEC and NYSE requirements.

As a foreign private issuer, in reliance on NYSE rules that permit a foreign private issuer to follow the corporate governance practices of its home country, we will be permitted to follow certain Canadian corporate governance practices instead of those otherwise required under the corporate governance standards for U.S. domestic issuers. We expect to follow Canadian home country practices with regard to obtaining shareholder approval for certain dilutive events. We may in the future elect to follow Canadian home country practices with regard to other matters such as the formation and composition of our Board of Directors, our audit, human resources and governance and nominating committees and separate sessions of independent directors. Accordingly, our investors may not be afforded the same protection as provided under NYSE corporate governance rules. Following Canadian home country governance practices as opposed to the requirements that would otherwise apply to a U.S. company listed on the NYSE may provide less protection than is accorded to investors in U.S. domestic issuers.

As a foreign private issuer, we will not be subject to the provisions of Regulation FD or U.S. proxy rules and will be exempt from filing certain Exchange Act reports, which could result in the Securities being less attractive to investors.

As a foreign private issuer, we will be exempt from a number of requirements under U.S. securities laws that apply to public companies that are not foreign private issuers. In particular, we will be exempt from the

Table of Contents

rules and regulations under the Exchange Act related to the furnishing and content of proxy statements, and our officers, directors and principal shareholders will be exempt from the insider reporting and short-swing profit recovery provisions contained in Section 16 of the Exchange Act. In addition, we will not be required under the Exchange Act to file annual and current reports and financial statements with the SEC as frequently or as promptly as U.S. domestic companies whose securities are registered under the Exchange Act and we will generally be exempt from filing quarterly reports with the SEC under the Exchange Act. We will also be exempt from the provisions of Regulation FD, which prohibits the selective disclosure of material non-public information to, among others, broker-dealers and holders of a company's securities under circumstances in which it is reasonably foreseeable that the holder will trade in the company's securities on the basis of the information. Even though we intend to comply voluntarily with Regulation FD, these exemptions and leniencies will reduce the frequency and scope of information and protections to which you are entitled as an investor.

We will lose our foreign private issuer status if a majority of our shares are held by U.S. persons and a majority of our directors or executive officers are U.S. citizens or residents or we fail to meet additional requirements necessary to avoid loss of foreign private issuer status. Although we have elected to comply with certain U.S. regulatory provisions, loss of foreign private issuer status would make compliance with such provisions mandatory. The regulatory and compliance costs to us under U.S. securities laws as a U.S. domestic issuer may be significantly higher than the costs we incur as a Canadian foreign private issuer eligible to use MJDS.

If we cease to be a foreign private issuer, we would not be eligible to use MJDS or other foreign issuer forms and will be required to file periodic and current reports and registration statements on U.S. domestic issuer forms with the SEC, which are more detailed and extensive than the forms available to a foreign private issuer. We may also be required to modify certain of our policies to comply with the governance obligations of U.S. domestic issuers. Such modifications will involve additional costs. In addition, we would lose our ability to rely upon exemptions from certain corporate governance requirements that are available to foreign private issuers with securities listed on the NYSE.

We have not yet completed our determination regarding whether our existing internal controls over financial reporting are compliant with the requirements of Section 404 of theSarbanes-Oxley Act of 2002.

We currently maintain disclosure controls and procedures and internal control over financial reporting pursuant to the Canadian Securities Administrators National Instrument 52-109 — Certification of Disclosure in Issuers' Annual and Interim Filings, and are undergoing an assessment of our current internal controls procedures to determine whether we are in compliance with the requirements of Section 404(a) of theSarbanes-Oxley Act of 2002, as amended, or Sarbanes-Oxley, and the related rules of the SEC and the Public Company Accounting Oversight Board.

Pursuant to Section 404(b) of Sarbanes-Oxley and the related rules adopted by the SEC and the Public Company Accounting Oversight Board, starting with the annual report to be filed by us with the SEC for the year ended December 31, 2017, our independent auditors will be required to attest to the effectiveness of our internal control over financial reporting. The process of confirming that our independent auditors will provide the required attestation in respect of our annual report has commenced and will require the investment of substantial additional time and resources, including by our Chief Financial Officer and other members of our senior management, as well as higher than anticipated operating expenses including independent auditor fees. Our failure to satisfy the requirements of Section 404 of Sarbanes-Oxley on an ongoing and timely basis, or any failure in our internal controls, could result in the loss of investor confidence in the reliability of our financial statements, which in turn could negatively affect the trading price of our securities and could have a material adverse effect on our results of operations and harm our reputation. Further, we can provide no assurance that our independent auditors will be able to provide the required attestation. If we are required in the future to make changes to our internal controls over financial reporting, it could adversely affect our operations, financial reporting and/or results of operations and could result in an adverse opinion on internal controls over financial reporting from our independent auditors.

Table of Contents

AUDITORS

Our auditors are Ernst & Young LLP, Chartered Professional Accountants, Fortis Place, 5 Springdale Street, Suite 800, St. John's, Newfoundland and Labrador A1E 0E4. Ernst & Young LLP report that they are independent of us in accordance with the Rules of Professional Conduct of the Association of Chartered Professional Accountants of Newfoundland and Labrador and in accordance with the applicable rules and regulations of the SEC and the Public Company Accounting Oversight Board.

The auditors of ITC are Deloitte & Touche LLP, located in Detroit, Michigan. Deloitte & Touche LLP has audited the consolidated financial statements and financial statement schedule of ITC as at December 31, 2015 and December 31, 2014 and for the years ended December 31, 2015, 2014 and 2013 together with the notes thereto and the auditor's report thereon dated February 25, 2016, which are included in the ITC Business Acquisition Report and the Management Information Circular incorporated by reference in this Prospectus. Deloitte & Touche LLP, certified public accountants, are independent with respect to ITC within the meaning of the Securities Act, and the applicable rules and regulations thereunder adopted by the SEC and the Public Company Accounting Oversight Board.

LEGAL MATTERS

Unless otherwise specified in a Prospectus Supplement relating to a specific offering of Securities, certain legal matters relating to the offering of Securities will be passed upon on our behalf by Davies Ward Phillips & Vineberg LLP, Toronto. At the date hereof, partners and associates of Davies Ward Phillips & Vineberg LLP own beneficially, directly or indirectly, less than 1% of any of our securities or any of our associates or affiliates.

ENFORCEABILITY OF CIVIL LIABILITIES

We are incorporated under the laws of the Province of Newfoundland and Labrador, Canada. The majority of our directors and officers, and some of the experts named in this Prospectus, are residents of Canada, and all or a substantial portion of their assets, and a substantial portion of our assets, are located outside the U.S. We have appointed an agent for service of process in the U.S., but it may be difficult for holders of Securities who reside in the U.S. to effect service within the U.S. upon those directors, officers and experts who are not residents of the U.S. It may also be difficult for holders of the Securities who reside in the U.S. to realize in the U.S. upon judgments of courts of the U.S. predicated upon our civil liability and the civil liability of our directors and officers and experts under U.S. federal securities laws.

We have filed with the SEC, concurrently with the registration statement on Form F-10, an appointment of agent for service of process on Form F-X. Under the Form F-X, we have appointed CT Corporation System, 111 Eighth Avenue, New York, New York 10011, as our agent for service of process in the U.S. in connection with any investigation or administrative proceeding conducted by the SEC, and any civil suit or action brought against us in a U.S. court arising out of or related to or concerning the offering of the Securities under the registration statement.

Two of our directors, Ms. Maura J. Clark and Ms. Margarita K. Dilley, reside outside of Canada and each has appointed Fortis Inc., Suite 1100, 5 Springdale Street, P.O. Box 8837, St. John's, Newfoundland and Labrador A1B 3T2 as agent for service of process. Investors are advised that it may not be possible to enforce judgments obtained in Canada against any person that resides outside of Canada, even if such person has appointed an agent for service of process.

Table of Contents

GLOSSARY

Unless we have indicated otherwise, or the context otherwise requires, references in this Prospectus to "Fortis", "we", "us" and "our" refer to Fortis Inc. and our consolidated subsidiaries.

"Annual Financial Statements" refers to our audited comparative consolidated financial statements as at December 31, 2015 and December 31, 2014 and for the fiscal years ended December 31, 2015 and 2014, together with the notes thereto and the auditors' report thereon dated February 17, 2016.

"Annual MD&A" refers to our Management Discussion and Analysis of financial condition and results of operations dated February 17, 2016 for the fiscal year ended December 31, 2015.

"Base Rate Complaints" refers to two complaints filed with FERC covering two refund periods running consecutively from November 12, 2013 through May 11, 2016 to which International Transmission Company, Michigan Electric Transmission Company, LLC and ITC Midwest LLC are subject, as described in detail in "Schedule E — ITC Historical Financial Statements and Management's Discussion and Analysis" in the Management Information Circular and in the interim financial statements of ITC included in the ITC Business Acquisition Report, in each case incorporated by reference in this Prospectus.

"Board of Directors" refers to our board of directors.

"Bonus Depreciation" refers to federal U.S. bonus tax depreciation.

"Canadian Co-trustee" means BNY Trust Company of Canada, in its capacity as Canadian co-trustee under the U.S. Indenture.

"Canadian Indenture" refers to the trust indenture dated July 2, 2009, between us and Computershare Trust Company of Canada.

"Central Hudson" refers to Central Hudson Gas & Electric Corporation.

"Common Shares" refers to our common shares.

"Debt Securities" refers to unsecured debt securities that may be issued by us under a Prospectus Supplement.

"Escrow Agent" refers to the financial institution authorized to carry on business as a trustee that will enter into a Subscription Receipt Agreement in connection with any issuance of Subscription Receipts.

"Escrowed Funds" refers to the gross proceeds from the sale of the Subscription Receipts, together with interest and income earned thereon.

"Exchange Act" refers to theU.S. Securities Exchange Act of 1934, as amended.

"Exchangeable Notes" refers to, collectively, our US$500 million 2.100% Notes due 2021 and our US$1,500 million 3.055% Notes due 2026.

"First Preference Shares" refers to our first preference shares.

"First Preference Shares, Series F" refers to our Cumulative Redeemable First Preference Shares, Series F.

"First Preference Shares, Series G" refers to our Cumulative Redeemable Five-Year Fixed Rate Reset First Preference Shares, Series G.

"First Preference Shares, Series H" refers to our Cumulative Redeemable Five-Year Fixed Rate Reset First Preference Shares, Series H.

"First Preference Shares, Series I" refers to our Cumulative Redeemable Floating Rate First Preference Shares, Series I.

"First Preference Shares, Series J" refers to our Cumulative Redeemable First Preference Shares, Series J.

"First Preference Shares, Series K" refers to our Cumulative Redeemable Fixed Rate Reset First Preference Shares, Series K.

Table of Contents

"First Preference Shares, Series M" refers to our Cumulative Redeemable Fixed Rate Reset First Preference Shares, Series M.

"FortisAlberta" refers to FortisAlberta Inc.

"GIC" refers to GIC Pte Ltd.

"Indentures" has the meaning set forth in the section entitled "Description of Securities Offered — Debt Securities".

"Initial Purchasers" refers to the initial purchasers of our Exchangeable Notes.

"Interim Financial Statements" refers to our unaudited comparative interim consolidated financial statements as at September 30, 2016 and for the three and nine months ended September 30, 2016 and 2015, together with the notes thereon.

"Interim MD&A" refers to our Management Discussion and Analysis of financial condition and results of operations for the three and nine months ended September 30, 2016.

"ITC" refers to ITC Holdings Corp.

"ITC Business Acquisition Report" means the business acquisition report dated November 23, 2016 with respect to the acquisition of ITC completed on October 14, 2016.

"ITC Regulated Operating Subsidiaries" refers, collectively, to International Transmission Company, Michigan Electric Transmission Company, LLC, ITC Midwest LLC and ITC Great Plains, LLC.

"Management Information Circular" refers to our Management Information Circular dated March 18, 2016 prepared in connection with our annual and special meeting of shareholders held on May 5, 2016.

"Outstanding First Preference Shares" refers to, collectively, our First Preference Shares, Series F; First Preference Shares, Series G; First Preference Shares, Series H; First Preference Shares, Series I; First Preference Shares, Series J; First Preference Shares, Series K; and First Preference Shares, Series M.

"Prospectus" refers to this short form base shelf prospectus, as amended or supplemented from time to time.

"Prospectus Supplement" refers to a prospectus supplement relating to an offering of Securities accompanying and incorporated by reference into this Prospectus.

"Release Conditions" refers to conditions for the exchange of Subscription Receipts into Common Shares, First Preference Shares, Second Preference Shares or Debt Securities, as applicable.

"Sarbanes-Oxley" refers to theSarbanes-Oxley Act of 2002, as amended.

"Second Preference Shares" refers to our second preference shares.

"Securities" refers to, collectively, Common Shares, First Preference Shares, Second Preference Shares, Subscription Receipts and/or Debt Securities.

"Securities Act" refers to theU.S. Securities Act of 1933, as amended.

"Selling Securityholder" refers to any of our securityholders that distributes Securities under this Prospectus and an accompanying Prospectus Supplement, which may include one or more of our wholly owned subsidiaries.

"Subscription Receipt Agreement" refers to the subscription receipt agreement to be entered into among us, one or more underwriters and the Escrow Agent providing for the issuance of Subscription Receipts.

"Subscription Receipts" refers to subscription receipts that may be issued by us under a Prospectus Supplement.

"UNS Electric" refers to UNS Electric, Inc.

"UNS Energy" refers to, collectively, Tucson Electric Power Company, UNS Gas, Inc. and UNS Electric, Inc.

"U.S. Indenture" refers to the trust indenture dated as of October 4, 2016 among us, the U.S. Trustee and the Canadian Co-trustee.

"U.S. Trustee" refers to The Bank of New York Mellon.

Table of Contents

Further, as used in this Prospectus, the abbreviations contained herein have the meanings set forth below.


CSPP		our Consumer Share Purchase Plan
DRIP		our Dividend Reinvestment Plan
EDGAR		Electronic Document Gathering and Retrieval System
ESPP		our Employee Share Purchase Plan
FERC		U.S. Federal Energy Regulatory Commission
ITC		ITC Holdings Corp.
LNG		liquefied natural gas
MJDS		Multi-Jurisdictional Disclosure System of the U.S. and Canada
MW		megawatt(s)
NYSE		New York Stock Exchange
ROE		return on common shareholders' equity
SEC		U.S. Securities and Exchange Commission
SEDAR		Canadian System for Electronic Document Analysis and Retrieval
TJ		terajoules
TSX		Toronto Stock Exchange
U.S.		United States of America
U.S. GAAP		U.S. generally accepted accounting principles

Table of Contents

FORTIS INC.

$500,000,000
COMMON SHARES

PROSPECTUS SUPPLEMENT

March 26, 2018

Scotiabank
TD Securities
Morgan Stanley
Wells Fargo Securities

Fortis (FTS) SUPPLSupplemental materials (foreign)