QUESTIONS AND ANSWERS ABOUT THE MERGER AND THE SPECIAL MEETING

The following are some questions that you may have regarding the Agreement and Plan of Reorganization, or the reorganization agreement, dated as of November 28, 2017, by and between Independent Bank Group, Inc., or Independent, and Integrity Bancshares, Inc., or Integrity, and the special meeting, and brief answers to those questions. Independent and Integrity advise you to read carefully the remainder of this proxy statement/prospectus because the information contained in this section does not provide all of the information that might be important to you with respect to the merger and the special meeting. Additional important information is also referred to under the caption “Where You Can Find More Information” beginning on page 119.

This document constitutes both a proxy statement of Integrity and a prospectus of Independent. It is a proxy statement because the board of directors of Integrity is soliciting proxies from Integrity’s shareholders using this document. It is a prospectus because Independent is offering shares of its common stock to Integrity shareholders as part of the merger consideration to be provided to holders of Integrity common stock in the merger.

Proposal One: to approve the reorganization agreement, pursuant to which Integrity will merge with and into Independent, with Independent being the surviving entity following the merger, which transaction is referred to herein as the merger and is further described in the section entitled “The Merger” beginning on page 50; and

Proposal Two: to approve the adjournment of the Integrity special meeting to a later date or dates if the board of directors of Integrity determines it is necessary to permit solicitation of additional proxies if there are not sufficient votes at the time of the Integrity special meeting to constitute a quorum or to approve the reorganization agreement.

No other business may be conducted at the Integrity special meeting.

The number of shares of Independent common stock to be issued and the amount of cash to be paid by Independent for each share of Integrity common stock will depend on the number of Integrity stock options that are exercised before closing and thus the total number of shares of Integrity common stock that are outstanding as of the closing. If, as anticipated, outstanding Integrity stock options to purchase 168,900 shares of Integrity common stock are exercised and, therefore, the number of shares of Integrity common stock was equal to 5,034,952 shares as of closing, there are Integrity stock options to purchase 76,000 shares of Integrity common stock that remain outstanding and unexercised on the tangible equity determination date and that the aggregate amount to be paid to cash out such unexercised Integrity stock options is $994,080, and Integrity’s tangible equity equaled or exceeded $84.0 million on the tangible equity determination date, each share of Integrity common stock would be exchanged for 0.41155 of a share of Independent common stock and $6.08 in cash. However, as a consequence of not knowing the exact fraction of a share of Independent common stock that will be exchanged for each share of Integrity common stock in connection with the merger and because the price per share of Independent common stock will fluctuate between now and the effective date of the merger, the holders of Integrity common stock will not know the exact value of the Independent common stock, and, therefore, the exact value of the per share merger consideration, that the holders of shares of Integrity common stock will receive for each such share in the merger until the merger’s effective date.

The number of shares of Integrity common stock outstanding is expected to increase by 168,900 as a result of the exercise of Integrity stock options prior to the merger’s effective time.

As noted, the per share merger consideration is dependent in part upon the number of shares of Integrity common stock outstanding at the effective time of the merger. Integrity currently estimates that outstanding Integrity stock options to purchase 168,900 shares of Integrity common stock will be exercised, and that, as

a result, 5,034,952 shares of Integrity common stock will be issued and outstanding and Integrity stock options to purchase 76,000 shares of Integrity common stock will remain outstanding and unexercised at the effective time of the merger. The reorganization agreement provides for the cashout of any Integrity stock options that are outstanding and unexercised in connection with the merger. For more detail on these estimates, please see “The Merger—Estimated Number of Shares of Integrity Common Stock to be Issued and Outstanding on the Closing Date” beginning on page 51.

Based on the assumptions set forth above and the closing price of Independent’s common stock as of January 25, 2018, of $74.25 per share, we estimate Integrity shareholders would receive merger consideration with a value of $36.64 for each share of Integrity common stock they hold immediately prior to the effective time of the merger and with an aggregate value to all holders of Integrity common stock of $184.5 million. The aggregate value of the shares of Independent common stock to be issued to the Integrity shareholders in connection with the merger and the value of the fraction of a share of Independent common stock to be issued in exchange for each share of Integrity common stock in connection with the merger will increase or decrease between the date hereof and the effective time of the merger depending on a number of factors, including fluctuations in the market price of Independent common stock and the number of shares Integrity common stock outstanding immediately prior to the merger’s effective time.

For further explanation of how the Integrity’s adjusted tangible equity will be calculated, the effect on the merger consideration to be paid if Integrity’s adjusted tangible equity is less than $84.0 million on the tangible equity determination date, the number of shares of Integrity common stock that will be issued and outstanding immediately prior to the merger’s effective time, and other estimates, please refer to “The Merger” beginning on page 50 of this proxy statement/prospectus.

As noted above, pursuant to the terms of the reorganization agreement, the amount of aggregate cash consideration paid by Independent to shareholders of Integrity will also be reduced by the aggregate amount of cash paid by Independent to the holders of Integrity stock options who do not exercise their Integrity stock options by the tangible equity determination date. Management estimates that Integrity stock options to acquire 76,000 shares of Integrity common stock will remain outstanding and unexercised on the tangible

equity determination date. In this event, and based on the assumptions set forth above, the aggregate payment to cash out such unexercised Integrity stock options would be $994,080 and the cash portion of the merger consideration would be reduced from $31.6 million to approximately $30.6 million.

For purposes of determining the estimated tangible equity of Integrity, that amount of Integrity’s tangible equity will be increased by the amount of the consolidated net income of Integrity or decreased by the amount of the consolidated net loss of Integrity from January 1, 2018, through the tangible equity determination date and reduced by the amount of certain costs and expenses to be incurred by Integrity in connection with the merger. Integrity currently estimates that it will have consolidated net income of between $3.3 million and $3.6 million from January 1, 2018, through April 24, 2018, which would be the tangible equity determination date assuming that the closing date of the merger will be April 30, 2018, and the effective date of the merger will be May 1, 2018. The tangible equity of Integrity will be increased by the proceeds received from the exercise of the Integrity stock options.

The table set forth below shows the range of estimates for the amounts that will affect the calculation of Integrity’s adjusted tangible equity, assuming the closing of the merger occurs on April 30, 2018:

If Integrity achieves the estimates in the range set forth above, Integrity’s adjusted tangible equity as of the closing date would be greater than $84.0 million, and, thus, the cash portion of the merger consideration would not be adjusted downward for a shortfall in adjusted tangible equity. No upward adjustment of the merger consideration will be made as a result of Integrity adjusted tangible equity exceeding $84.0 million at the tangible equity determination date. However, if Integrity’s tangible equity is greater than $84.0 million on the tangible equity determination date, then on the day prior to the closing date, Integrity may distribute to its shareholders an amount equal to the difference between the actual amount of Integrity tangible equity on the tangible equity determination date less $84.0 million.

The amounts in the table above are only estimates and are based upon several assumptions, many of which are beyond the control of Integrity and Integrity Bank. Accordingly, the actual amount of Integrity’s adjusted tangible equity at the tangible equity determination date may vary from these estimated amounts. Integrity will not resolicit proxies from holders of its common stock in the event that Integrity adjusted tangible equity is below $76.0 million on the tangible equity determination date and the cash portion of the merger consideration is adjusted downward as Integrity has no right to do so under the reorganization agreement. For more information regarding how the Integrity adjusted tangible equity will be calculated and how Integrity has estimated what that amount will be on or about May 1, 2018, the anticipated effective date of the merger, please see “The Merger—Possible Downward Adjustment to the $31.6 million Merger Consideration” beginning on page 51.

Proposal One: FOR the approval of the reorganization agreement and the merger; and

Proposal Two: FOR the adjournment of the Integrity special meeting to a later date or dates if the board of directors of Integrity determines it is necessary to permit solicitation of additional proxies if there are not sufficient votes at the time of the Integrity special meeting to constitute a quorum or to approve the reorganization agreement and the merger.

The steps that a holder of Integrity common stock must follow to perfect his or her right of dissent are described in greater detail under the caption “The Merger—Dissenters’ Rights of Integrity Shareholders” starting on page 94, and this discussion is qualified by that description and by the text of the provisions of the TBOC relating to rights of dissent set forth in Appendix C hereto. The appraised fair value of any number of shares of Integrity common stock may be more or less than the value of the shares of the Independent common stock and cash payment that would be issued in exchange for that number of shares of Integrity common stock in the merger. If the holders of more than 5% of the outstanding shares of Integrity common stock dissent from the merger, Independent has the right to terminate the reorganization agreement and to not consummate the merger.

If you are a record holder, you may vote by proxy or you may attend the Integrity special meeting and vote in person the shares of Integrity common stock you are entitled to vote at the Integrity special meeting. If you are a record holder on the record date for the Integrity special meeting and want to vote your shares of Integrity common stock by proxy, simply indicate on the proxy card(s) applicable to your shares of Integrity common stock how you want to vote and sign, date and mail your proxy card(s) in the enclosed envelope as soon as possible, but in any event no later than the time necessary for your proxy card to be actually received by Integrity prior to the vote at the Integrity special meeting.

Your proxy card must be received by Integrity by no later than the time the polls close for voting at the Integrity special meeting for your vote to be counted at the Integrity special meeting.

Voting your shares by proxy will enable your shares of Integrity common stock to be represented and voted at the Integrity special meeting if you do not attend the special meeting and vote your shares in person.

If your shares of Integrity are held in “street name,” then you are not the shareholder of record. In order for you to vote the shares that you beneficially own and that are held in “street name” in person at the special meeting, you must bring a legal proxy from the broker, custodian or other nominee that was the record holder of your shares held in “street name” as of 5:00 p.m. on                 , 2018, confirming that you were the beneficial owner of those shares as of 5:00 p.m. on                 , 2018, stating the number of shares of which you were the beneficial owner that were held for your benefit at that time by that broker, custodian or other nominee and appointing you as the record holder’s proxy to vote the shares covered by that proxy at the special meeting.

If your shares are held in “street name” and you desire to change any voting instructions you have previously given to the record holder of the shares of which you are the beneficial owner, you should contact the broker, custodian or other nominee holding your shares in “street name” in order to direct a change in the manner your shares will be voted.

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SUMMARY

This summary highlights selected information from this proxy statement/prospectus and may not contain all of the information that is important to you regarding the merger and related matters. Independent and Integrity urge you to carefully read this entire document and the other information that is referred to in this proxy statement/prospectus or contained in the reports and documents incorporated by reference in this proxy statement/prospectus. These documents will give you a more complete description of the items for consideration at the special meeting. For more information about Independent and Integrity, see “Where You Can Find More Information” on page 119. Independent has included page references in this summary to direct you to other places in this proxy statement/prospectus where you can find a more complete description of the topics that Independent has summarized.

The Companies

Independent Bank Group, Inc.

1600 Redbud Boulevard, Suite 400

McKinney, Texas 75069-3257

(972) 562-9004

www.ibtx.com

Independent, a Texas corporation, is a bank holding company registered under the Bank Holding Company Act of 1956, as amended, or the BHC Act. Through Independent Bank, its wholly owned subsidiary bank, which is a Texas state bank, Independent provides a wide range of relationship driven, commercial banking products and services. Independent currently operates a total of 70 full-service banking centers in the Dallas/North Texas metropolitan area, including McKinney, Dallas, Fort Worth and Sherman/Denison, the greater Austin, Texas, area, including Austin and Waco, the Houston, Texas metropolitan area and the Colorado Front Range area, including Denver and Colorado Springs. As of September 30, 2017, on a consolidated basis, Independent had total assets of approximately $8.9 billion, total loans of approximately $6.4 billion, total deposits of approximately $6.9 billion and shareholders’ equity of approximately $1.3 billion.

Independent’s common stock is traded on the NASDAQ Global Select Market under the symbol “IBTX.”

Integrity Bancshares, Inc.

4040 Washington Avenue

Houston, Texas 77007

(713) 335-8700

Integrity Bancshares, Inc., a Texas corporation, is a bank holding company registered under the BHC Act. Integrity conducts its banking operations through its wholly owned subsidiary, Integrity Bank SSB, a Texas state savings bank, that operates four full service banking locations in the Houston, Texas metropolitan area. As of September 30, 2017, Integrity, on a consolidated basis, reported total assets of approximately $805 million, total loans of approximately $661 million, total deposits of approximately $679 million and total equity capital of approximately $84.0 million.

Proposed Merger

The reorganization agreement is attached to this proxy statement/prospectus as Appendix A. Please read the entire reorganization agreement. It is the legal document that governs the merger.

Terms of the Merger (page 50)

The reorganization agreement provides for Independent to acquire all of the issued and outstanding securities of Integrity through the merger of Integrity with and into Independent, with Independent being the surviving corporation following the merger. If the shareholders of Integrity approve the reorganization agreement at the special meeting, and if the required regulatory approvals are obtained and the other conditions to the parties’ obligations to effect the merger are satisfied or are waived by the party entitled to do so, Independent and Integrity anticipate that the merger will be completed on May 1, 2018, although delays could occur.

Independent is the sole shareholder of Independent Bank, and Integrity is the sole shareholder of Integrity Bank. Upon the merger’s completion, both Independent Bank and Integrity Bank will be wholly owned subsidiaries of Independent. Pursuant to the reorganization agreement, immediately following the merger’s completion, Integrity Bank will merge with and into Independent Bank, with Independent Bank being the surviving bank following the bank merger.

The merger will be accounted for as an acquisition of Integrity and Integrity Bank by Independent and Independent Bank under the acquisition method of accounting in accordance with the Financial Accounting Standard Board’s Accounting Standard Codification Topic 805, “Business Combinations.”

Treatment of Shares of Integrity Common Stock (page 50)

As a result of the merger, holders of Integrity common stock will be entitled to receive whole shares of Independent common stock and a cash payment in exchange for their shares of Integrity common stock. Independent will pay cash in lieu of issuing fractional shares of Independent common stock. After the merger, the Integrity shareholders will no longer be owners of Integrity common stock. As a result of the merger, certificates of Integrity common stock will represent only the right to receive the merger consideration pursuant to the reorganization agreement. Integrity will cease to exist following the merger’s completion.

If the shareholders of Integrity approve the reorganization agreement and the merger, the necessary regulatory approvals of the merger are received, and the merger is completed, and assuming 5,034,952 shares of Integrity common stock are outstanding immediately prior to the merger (which assumes that outstanding Integrity stock options to acquire 168,900 Integrity common stock are exercised prior to the tangible equity determination date), there are unexercised Integrity stock options to purchase 76,000 shares of Integrity common stock and that the aggregate amount to be paid to cash out such unexercised Integrity stock options is $994,080, Integrity has adjusted tangible equity of at least $84.0 million on the tangible equity determination date and the price of Independent common stock is $74.25 per share (the closing price of Independent common stock on January 25, 2018), then, each of the shares of Integrity common stock then outstanding would be exchanged for 0.41155 of a share of Independent common stock and a cash payment of $6.08 and all of those outstanding shares of Integrity common stock would be exchanged for an aggregate of 2,072,131 shares of Independent common stock and approximately $30.6 million in cash. For more detail on this estimate, please see “The Merger—Estimated Number of Shares of Integrity Common Stock to be Issued and Outstanding on the Closing Date” on page 51.

Treatment of Integrity Stock Options (page 51)

Pursuant to the terms of the reorganization agreement, each outstanding and unvested Integrity stock option that is not fully vested and immediately exercisable will become fully vested upon the approval of the reorganization agreement and the merger by the holders of Integrity common stock. Upon such approval, all of the outstanding Integrity stock options will then no longer be subject to forfeiture and will be immediately exercisable. Each such Integrity stock option that is not exercised prior to the effective time of the merger will be automatically cashed out under the terms of the reorganization agreement and an option cancellation agreement,

and the holder of each cashed out Integrity stock option will have the right to receive a cash payment in an amount equal to the difference between (i) the per share transaction value, minus the applicable exercise price per option share, or the per option share price, multiplied by the total number of option shares held by such nonexercising option holder. Such amount will be paid to the option holders within five business days following the closing date of the merger. Any amount paid by Independent to cash out the Integrity stock options will reduce the cash portion of the merger consideration. Management of Integrity anticipates that Integrity stock options to purchase 76,000 shares of Integrity common stock will remain outstanding and unexercised prior to the tangible equity determination date, which, based on the assumptions set forth above, would result in an aggregate payment of $994,080 to cash out such unexercised Integrity stock options.

Estimated Number of Shares of Integrity Common Stock to be Issued and Outstanding on the Closing Date (page 51)

The number of shares of Independent common stock and cash payment amount to be received by the Integrity shareholders with respect to their shares of Integrity common stock is dependent, among other factors, upon the number of shares of Integrity common stock issued and outstanding immediately prior to the effective time of the merger. As of                     , 2018, the record date for the Integrity special meeting,                  shares of Integrity common stock were issued and outstanding, and Integrity stock options to purchase                  shares of Integrity common stock were outstanding and unexercised. If Integrity stock outstanding options to purchase 168,900 shares of Integrity common stock are exercised, 5,034,952 shares of Integrity common stock would be issued and outstanding immediately prior to the effective time of the merger. For more detail on these estimates, please see “The Merger—Estimated Number of Shares of Integrity Common Stock to be Issued and Outstanding on the Closing Date” on page 51. Shares of Integrity common stock acquired upon the exercise of Integrity stock options will be exchanged for shares of Independent common stock and a cash payment in the merger on the same basis as all other shares of Integrity common stock outstanding immediately prior to the effective time of the merger.

Possible Downward Adjustment to the $31.6 million Merger Consideration (page 51)

The $31.6 million cash consideration will be reduced, on a dollar-for-dollar basis, if the adjusted tangible equity of Integrity is less than $84.0 million on the tangible equity determination date. Under those circumstances, the aggregate cash consideration would be reduced by the difference between $84.0 million and the amount Integrity’s tangible equity on the tangible equity determination date.

As noted above, the amount paid by Independent to cash out outstanding and unexercised Integrity stock options will reduce the aggregate cash portion of the merger consideration. Management of Integrity anticipates that Integrity stock options to purchase 76,000 shares of common stock will remain outstanding and unexercised, and that, based upon the closing price of Independent common stock of $74.25 on January 25, 2018, Independent would make an aggregate payment of approximately $994,080 to cash out such unexercised Integrity stock options. In this event, the aggregate cash portion of the merger consideration would be reduced by $994,080 from $31.6 million to approximately $30.6 million.

Pursuant to the terms of the reorganization agreement, the adjusted tangible equity of Integrity will be determined from Integrity’s financial statements prepared in accordance with generally accepted accounting principles, consistently applied, or GAAP, adjusted as provided for below. Any unrealized gains or losses in investment securities will also be excluded from the calculation of adjusted tangible equity.

As of December 31, 2017, the tangible equity of Integrity (calculated in accordance with GAAP) was $85.8 million. For purposes of determining the estimated tangible equity of Integrity, that amount of Integrity’s adjusted tangible equity will be increased by the amount of the consolidated net income of Integrity or decreased by the amount of the consolidated net loss of Integrity from January 1, 2018, through the tangible equity determination date and reduced by the amount of certain costs and expenses to be incurred by Integrity in connection with the merger. Integrity currently estimates that it will have consolidated net income of between

$3.3 million and $3.6 million from January 1, 2018, through April 24, 2018, which would be the tangible equity determination date assuming that the closing date of the merger will be April 30, 2018, and the effective date of the merger will be May 1, 2018.

The table set forth below shows the range of estimates for the amounts that will affect the calculation of Integrity’s adjusted tangible equity, assuming the closing of the merger occurs on April 30, 2018:

If Integrity achieves the estimates in the range set forth above, Integrity’s adjusted tangible equity as of the closing date would be greater than $84.0 million, and, thus, the cash consideration would not be adjusted downward for a shortfall.

The amounts in the table above are only estimates and are based upon several assumptions, many of which are beyond the control of Integrity and Integrity Bank. Accordingly, the actual amount of Integrity’s adjusted tangible equity at the tangible equity determination date may vary from these estimated amounts. Integrity will not resolicit proxies from holders of its common stock in the event that Integrity adjusted tangible equity is below $84.0 million on the tangible equity determination date and the cash portion of the merger consideration is adjusted downward as Integrity has no right to do so under the reorganization agreement. For more information regarding how the Integrity adjusted tangible equity will be calculated and how Integrity has estimated what that amount will be on or about May 1, 2018, the anticipated effective date of the merger, please see “The Merger—Possible Downward Adjustment to the $31.6  million Cash Portion of the Merger Consideration” beginning on page 51.

Value of Merger Consideration to be Received (page 54)

If the necessary shareholder and regulatory approvals are obtained and the merger is completed, 5,034,952 shares of Integrity common stock are outstanding immediately prior to the merger (which is expected to be the case if Integrity stock options to purchase 168,900 shares of Integrity common stock are exercised after the date of this proxy statement/prospectus), there are Integrity stock options to purchase 76,000 shares of Integrity common stock that remain outstanding and unexercised and that the aggregate payment to cash out such unexercised Integrity stock options is $994,080, the adjusted tangible equity of Integrity is at least $84.0 million at the tangible equity determination date, each share of Integrity common stock then outstanding would be exchanged for 0.41155 of a share of Independent common stock and $6.08 per share in cash. Independent’s common stock is listed on the NASDAQ Global Select Market under the symbol “IBTX.”

Based on the assumptions set forth above and the closing price of Independent’s common stock as of January 25, 2018, of $74.25 per share, we estimate Integrity shareholders would receive merger consideration with a value of $36.64 for each share of Integrity common stock they hold immediately prior to the effective time of the merger and with an aggregate value to all holders of Integrity common stock of $184.5 million. The aggregate value of the shares of Independent common stock to be issued to the Integrity shareholders in

connection with the merger and the value of the fraction of a share of Independent common stock to be issued in exchange for each share of Integrity common stock in connection with the merger will increase or decrease between the date hereof and the effective time of the merger depending on a number of factors, including fluctuations in the market price of Independent common stock.

The amounts in each of the tables below have been calculated based on a number of assumed stock prices and 5,034,952 outstanding shares of Integrity common stock assuming the exercise of outstanding Integrity stock options to purchase 168,900 shares of Integrity common stock and an aggregate payment of $994,080 to cash out unexercised Integrity stock options to purchase 76,000 shares of Integrity common stock. Table 1 assumes that Integrity will have adjusted tangible equity of $84.0 million (as calculated in accordance with the terms of the reorganization agreement) on the tangible equity determination date; Table II assumes that Integrity will have adjusted tangible equity of $76.0 million on the tangible equity determination date.

The actual price at which a share of Independent common stock is trading in the market at the effective time of the merger may be materially less or more than any of the assumed stock prices in each of the tables below and the price and may be materially less or more than the assumed stock prices used for determining the value of the merger consideration shown in each of the tables below. As a result, the actual amounts and values of the merger consideration received by the Integrity shareholders in the merger may differ materially from any of the amounts and values set forth in either or both of the following tables.

Table I

Table II

Other Financial Aspects of the Merger (page 56)

If Integrity’s tangible equity is greater than $84.0 million on the tangible equity determination date, then on the closing date, Integrity may distribute to its shareholders an amount equal to the difference between the actual amount of tangible equity on the tangible equity determination date less $84.0 million.

Material U.S. Federal Income Tax Consequences (page 89)

The merger is intended to qualify as a reorganization within the meaning of Section 368(a) of the Internal Revenue Code, as amended, or the Code, for U.S. federal income tax purposes, and the closing is conditioned upon the receipt by Independent of an opinion from Andrews Kurth Kenyon LLP, special counsel to Independent, and the receipt by Integrity of an opinion from Jackson Walker L.L.P., counsel to Integrity, to the effect that the merger so qualifies. This summary of U.S. federal income tax consequences assumes that the merger will be consummated as described in the reorganization agreement and this proxy statement/prospectus and that Independent and Integrity will not waive the opinion condition described in “The Merger—Material U.S. Federal Income Tax Consequences of the Merger—Tax Opinions.” If the merger qualifies as such a reorganization, the material U.S. federal income tax consequences of the merger to a U.S. holder of Integrity common stock will be as follows: holders of Integrity common stock generally will recognize gain (but not loss) with respect to their Integrity common stock. The gain a U.S. holder of Integrity common stock recognizes generally will be equal to the lesser of cash received (excluding any cash received in lieu of a fractional share of Independent common stock) or gain realized in the merger. The amount of gain realized will equal an amount by which the cash plus the fair market value of the Independent common stock, at the effective time of the merger, exceeds the adjusted tax basis in the Integrity common stock to be surrendered in exchange therefor.

For further information, please refer to “The Merger—Material U.S. Federal Income Tax Consequences of the Merger.” The U.S. federal income tax consequences described above may not apply to all holders of Integrity common stock. The tax consequences to a holder of Integrity common stock will depend on his or her individual situation. Accordingly, we strongly urge holders of Integrity common stock to consult their tax advisors for a full understanding of the particular tax consequences of the merger to them.

Fairness Opinion of Financial Advisor to Integrity (page 59)

Sandler O’Neill & Partners, L.P., or Sandler O’Neill, has delivered a written opinion, dated November 28, 2017, to the board of directors of Integrity to the effect that, as of the date of the opinion, based upon and subject to the procedures followed, assumptions made, matters considered and qualifications and limitations set forth in the opinion, the aggregate merger consideration was fair to the holders of Integrity common stock from a financial point of view. This opinion is attached to this proxy statement/prospectus as Appendix B. Integrity shareholders are urged to read the opinion carefully in its entirety. Sandler O’Neill’s opinion speaks only as of the date of the opinion and was necessarily based on financial, economic, market and other conditions as they existed on, and the information made available to Sandler O’Neill as of, the date of Sandler O’Neill’s opinion. The opinion of Sandler O’Neill is not a recommendation to any Integrity shareholder as to how to vote on the proposal to approve the reorganization agreement and the merger. You should read this opinion completely to understand the procedures followed, matters considered and limitations on the reviews undertaken by Sandler O’Neill in providing its opinion.

Independent Plans to Continue Payment of Quarterly Dividends (page 108)

Independent paid a cash dividend of $0.10 per share to its shareholders in each of the four quarters of 2017 and in the first quarter of 2018. Independent intends to continue paying quarterly cash dividends following the merger.

Ownership of Independent After the Merger

Based on 28,254,893 shares of Independent common stock outstanding as of January 25, 2018, and Independent issuing a total of 2,072,131 shares of Independent common stock to the shareholders of Integrity in connection with the merger, the former Integrity shareholders would own approximately 7% of the shares of Independent common stock that would be outstanding immediately after such shares are issued in connection with the merger. Such ownership percentage will be reduced by any future issuances of shares of Independent common stock.

Market Prices of Independent Common Stock (page 106)

Shares of Independent common stock are listed for trading on the NASDAQ Global Select Market under the symbol “IBTX.” On November 27, 2017, the last trading day before the merger was announced, Independent common stock closed at $64.05 per share. On January 25, 2018, Independent common stock closed at $74.25 per share. The market price of Independent common stock will fluctuate prior to the merger. You should obtain the most recent closing price for Independent common stock on the NASDAQ Global Select Market prior to deciding how to vote. Shares of Integrity common stock are not traded on any national securities exchange or on an established public trading market and no quotations of any market price exists for shares of Integrity common stock.

Integrity Special Meeting (page 45)

The special meeting of shareholders of Integrity will be held on                     , 2018, at              a.m./p.m. Central Time, at                     , Houston, Texas                 . At the Integrity special meeting, holders of shares of Integrity common stock will be asked to consider and vote on the following:

Integrity Record Date Set at                     , 2018; Two-Thirds Shareholder Vote Required to Approve the Reorganization Agreement and the Merger (page 47-48)

You may vote on the proposals to come before special meeting of Integrity shareholders if you owned shares of Integrity common stock of record as of 5:00 p.m. on                     , 2018. You can cast one vote for each share of Integrity common stock that you owned of record at that time. As of January 25, 2018, there were 4,866,092 shares of Integrity common stock outstanding.

Approval of the reorganization agreement and the merger requires the affirmative vote of the holders of at least two-thirds of the shares of Integrity common stock outstanding and entitled to vote as of 5:00 p.m. on the record date. If a holder of Integrity common stock fails to vote, it will have the effect of a vote against the

reorganization agreement and the merger. The affirmative vote of a majority of the shares of Integrity common stock that are present in person or by proxy at the Integrity special meeting is required to approve the adjournment of the Integrity special meeting.

A holder of Integrity common stock may vote his or her shares of Integrity common stock by attending the special meeting and voting in person or by completing and mailing the enclosed proxy card. If you are the record holder of such shares, you can revoke your proxy at any time before the vote is taken at the Integrity special meeting by sending a written notice revoking the proxy or submitting a later-dated proxy to James M. McElray, Executive Vice President and Chief Financial Officer of Integrity, which notice or later dated proxy must be received no later than immediately prior to the vote at the Integrity special meeting. You may also revoke your proxy by voting in person at the Integrity special meeting. If you receive a notice of special meeting and a proxy statement/prospectus directly from Integrity, you are deemed a holder of record. If your shares of Integrity common stock are held in “street name” and you desire to change any voting instructions you have previously given to the record holder of such shares of Integrity common stock of which you are the beneficial owner, you should contact the broker, custodian or other nominee holding such shares in “street name” in order to direct a change in the manner your shares of Integrity common stock will be voted. See “The Integrity Special Meeting—Voting of Proxies by Holders of Record,” “—Attending the Meeting; Voting in Person” and “—Revocation of Proxies.”

Integrity’s Reasons for the Merger and Recommendation of Integrity’s Board of Directors (page 58)

Based on the reasons discussed elsewhere in this proxy statement/prospectus, the board of directors of Integrity believes that the merger is fair, from a financial point of view to, and in the best interests of, the shareholders of Integrity and unanimously recommends that you vote FOR the proposal to approve the reorganization agreement and the merger. For a discussion of the circumstances surrounding the merger and the factors considered by Integrity’s board of directors in approving the reorganization agreement, see pages 59 and 60.

Certain Shareholders of Integrity are Expected to Vote Their Shares of Integrity Common Stock for Approval of the Reorganization Agreement (page 40)

The directors of Integrity and certain entities that they represent have entered into an agreement to vote the shares of Integrity common stock that they control in favor of approval of the reorganization agreement and the merger and in the manner most favorable to the consummation of the merger and the transactions contemplated by the reorganization agreement; provided, however, that the Integrity shareholders who entered into the voting agreement would be permitted to vote to accept a superior proposal to acquire Integrity (as “superior proposal” is defined in the reorganization agreement). As of the Integrity record date, 1,130,526 shares of Integrity common stock, or     % of the                  shares of Integrity common stock then outstanding and entitled to vote at the Integrity special meeting, were bound by the voting agreement.

Effective Time of the Merger (page 73)

The merger will become effective at the date and time specified in the certificate of merger to be filed with the Texas Secretary of State. If Integrity shareholders approve the reorganization agreement and the merger at the special meeting, and if all necessary regulatory approvals are obtained and the other conditions to the parties’ respective obligations to effect the merger are satisfied or are waived by the party entitled to do so, Independent anticipates that the merger will be completed and effective on May 1, 2018, although delays in the completion of the merger could occur.

Integrity and Independent cannot assure you that the necessary shareholder and regulatory approvals will be obtained or that the other conditions to completion of the merger can or will be satisfied. See “Risk Factors—Risks Related to the Merger—The merger of Independent and Integrity may not be completed.”

Exchange of Integrity Stock Certificates (page 72)

After the effective time of the merger, the Integrity shareholders will receive a form of letter of transmittal and instructions from Equiniti Trust Company, acting as Independent’s exchange and transfer agent, or the exchange agent, describing the procedures for surrendering their stock certificates representing shares of Integrity common stock in exchange for shares of Independent common stock and a cash payment. The shares of Independent common stock issuable in exchange for the shares of Integrity common stock will be issued solely in uncertificated book-entry form and a holder’s shares of Independent common stock will be reflected in the shareholder’s account established in the Direct Registration System by Independent’s stock transfer agent. Please do not send Integrity or Independent any of your Integrity stock certificates until you receive these instructions.

Conditions to Completion of the Merger (page 78)

The completion of the merger depends on a number of conditions being satisfied. These include, among others:

In addition to the conditions listed above, Integrity’s obligations to complete the merger is subject to the satisfaction of the following conditions:

In addition to the conditions listed above, Independent’s obligation to complete the merger is subject to the satisfaction of the following conditions:

Additionally, the completion of the merger depends on the effectiveness of the following agreements, which agreements will not become effective until the effective time of the merger:

Any condition to the completion of the merger other than the required shareholder and regulatory approval and the absence of an order prohibiting the merger, may be waived in writing by the party to the reorganization agreement entitled to the benefit of such condition. A party to the reorganization agreement could choose to complete the merger even though a condition has not been satisfied, as long as permitted by applicable law. Neither Independent nor Integrity can be certain when or if the conditions to the merger will be satisfied or waived, or that the merger will be completed.

Regulatory Approvals Required for the Merger (page 94)

The acquisition of Integrity by Independent requires the approval of the Board of Governors of the Federal Reserve System, or Federal Reserve. In addition, the bank merger requires the approval of the Federal Deposit Insurance Corporation, or the FDIC, and the Texas Department of Banking, or TDB. On January 12, 2018, Independent, Independent Bank and Integrity Bank filed applications with the Federal Reserve, the FDIC and the TDB to obtain approval of the merger and the bank merger. Independent expects to obtain all necessary regulatory approvals, although Independent cannot be certain if or when Independent will obtain them.

Amendment or Waiver of the Reorganization Agreement (page 85)

Independent and Integrity may amend the reorganization agreement and each party may waive its right to require the other party to adhere to any term or satisfy any condition of the reorganization agreement in accordance with the terms of the reorganization agreement. However, the merger consideration to be received by the shareholders of Integrity pursuant to the terms of the reorganization agreement may not be decreased after shareholder approval of the reorganization agreement without the further approval of the Integrity shareholders.

No Solicitation (page 76)

Pursuant to the reorganization agreement, Integrity agreed that it will not, and that it will cause Integrity Bank and its employees, directors, officers, financial advisors or agents of Integrity and Integrity Bank not to, propose to, solicit, knowingly encourage, initiate or participate in any negotiations or discussions with any third party with respect to any proposal that could reasonably be expected to lead to an acquisition proposal as described in the reorganization agreement, disclose to any third party any information concerning the business,

properties, books or records of it in connection with any acquisition proposal, or cooperate with any third party to make any acquisition proposal. Promptly upon receipt of any unsolicited offer, Integrity will communicate to Independent the terms of any proposal or request for information and the identity of the parties involved.

Provided that Integrity has complied with the foregoing restrictions, if after the date of the reorganization agreement but prior to the closing of the merger, Integrity receives a bona fide, unsolicited written acquisition proposal, it may engage in negotiations and discussions with, and furnish any information and other access to, any person making such acquisition proposal if, and only if, Integrity’s board of directors determines in good faith, after consultation with outside legal and financial advisors, that such acquisition proposal is, or is reasonably, capable of becoming more favorable to Integrity’s shareholders from a financial point of view than the merger with Independent and the failure of Integrity’s board of directors to furnish such information or access or enter into such discussions or negotiations would be materially inconsistent with its fiduciary duties to the shareholders of Integrity and Integrity obtains an appropriately executed confidentiality agreement from such third party.

Termination of the Reorganization Agreement (page 85)

Independent and Integrity can mutually agree at any time to terminate the reorganization agreement without completing the merger. In addition, either Independent or Integrity may decide, without the consent of the other, to terminate the reorganization agreement if:

Integrity may terminate the reorganization agreement, without the consent of Independent, if:

In addition, Independent may terminate the reorganization agreement, without the consent of Integrity, if:

Termination Fee (page 86)

To compensate Independent for entering into the reorganization agreement, taking actions to consummate the transactions contemplated by the reorganization agreement and incurring the related costs and expenses and other losses and expense, including foregoing the pursuit of other opportunities, the reorganization agreement provides that Integrity will pay to Independent a termination fee of $4,650,000 if the reorganization agreement is terminated:

Except with respect to termination fees and expenses, as discussed above, in the event of the termination of the reorganization agreement without breach by any party, the reorganization agreement will be void and have no effect, without liability on the part of any party or the directors, officers or shareholders of any party, except as specifically contemplated in the reorganization agreement.

Some of the Directors and Officers of Integrity Have Financial Interests in the Merger that Differ from Your Interests (page 87)

Some of the directors and officers of Integrity have interests in the merger that differ from, or are in addition to, their interests as shareholders of Integrity. These interests include:

Comparison of Rights of Shareholders of Integrity and Independent (page 113)

Integrity is a Texas corporation that is a registered bank holding company, and the rights of shareholders of Integrity are governed by Texas law and Integrity’s certificate of formation and bylaws. Independent is a Texas corporation that is a registered bank holding company, and the rights of Independent’s shareholders are governed by Texas law and Independent’s certificate of formation and bylaws. Upon completion of the merger, shareholders of Integrity common stock will become shareholders of Independent and their rights as shareholders of Independent will be governed by Independent’s certificate of formation and bylaws, in addition to Texas law. Independent’s certificate of formation and bylaws will not be amended in the merger, but could be later restated, amended or, with respect to the bylaws, repealed.

Dissenters’ Rights of the Holders of Integrity Common Stock (page 94)

The holders of Integrity common stock have the right under Texas law to dissent from the merger and have the appraised fair value of their shares of Integrity common stock as of the date immediately preceding the effective date of the merger paid to them in cash. The appraised fair value of any particular number of shares of Integrity common stock as of such date may be more or less than the value of the merger consideration stock that a holder of that particular number of shares of Integrity common stock would be entitled to receive pursuant to the merger.

Persons having beneficial interests in Integrity common stock held of record in the name of another person, such as a broker, custodian or other nominee, must act promptly to cause the record holder to take the actions required under Texas law to exercise their dissenter’s rights.

In order to dissent, the holder of Integrity common stock must carefully follow the requirements of the TBOC, including providing Integrity, prior to the Integrity special meeting, with a written objection to the merger that states that he or she will exercise his or her right to dissent with respect to his or her shares of Integrity common stock if the holders of the Integrity common stock approve the reorganization agreement and the merger, and the merger is completed. These steps for perfecting the right of dissent are summarized under the caption “—Dissenters’ Rights of Integrity Shareholders” on page 94. The provisions of the TBOC pertaining to dissenters’ rights are attached to this proxy statement/prospectus as Appendix C and the summaries of those provisions in this proxy statement/prospectus should be read in conjunction with, and are qualified in their entirety by, those provisions of the TBOC.

If you intend to exercise dissenters’ rights as to shares of Integrity common stock that you hold, you should read the provisions of the TBOC governing dissenters’ rights carefully and consult with your own legal counsel. Each holder of Integrity common stock should also remember that if he or she returns a signed proxy card, but fails to provide instructions on that proxy card that his or her shares of Integrity common stock are to be voted

against the approval of the reorganization agreement and the merger, such Integrity shareholder’s shares of Integrity common stock will be considered to have voted in favor of the reorganization agreement and the merger. In that event, such Integrity shareholder will not be able to assert dissenters’ rights as to his or her shares of Integrity common stock.

If the Integrity shareholders approve the reorganization agreement, a holder of Integrity common stock who (i) delivers to the president and the secretary of Integrity a written objection to the merger prior to the Integrity special meeting that states that such holder will exercise his or her right to dissent if the reorganization agreement and the merger are approved and the merger is completed and includes an address for notice of the effectiveness of the merger, (ii) votes his or her shares of Integrity common stock against approval of the reorganization agreement and the merger at the Integrity special meeting, (iii) not later than the 20th day after Independent sends such holder notice that the merger was completed, delivers to the president and secretary of Independent a written demand for payment of the fair value of his or her shares of Integrity common stock, which demand states that he or she holds shares of Integrity common stock and states the number of shares of Integrity common stock such holder owns, his or her estimate of the fair value of such shares and an address to which a notice relating to the dissent and appraisal procedures may be sent, and (iv) not later than the 20^th day after he or she makes that demand for payment, submits to Independent the certificates representing his or her shares of Integrity common stock, will be entitled under the TBOC to receive the appraised fair value of his or her shares of Integrity common stock as of the date immediately prior to the effective time of the merger.

CERTAIN FINANCIAL INFORMATION REGARDING INDEPENDENT AND INTEGRITY

Selected Financial Information of Independent

The following selected historical consolidated financial information of Independent as of and for the nine months ended September 30, 2017 and 2016, has been derived from Independent’s unaudited consolidated financial statements as of and for the nine months ended September 30, 2017 and 2016, incorporated by reference in this proxy statement/prospectus. The following selected consolidated financial information of Independent as of and for the years ended December 31, 2016, 2015 and 2014, has been derived from Independent’s audited consolidated financial statements incorporated by reference in this proxy statement/prospectus, and the selected consolidated financial information as of and for the years ended December 31, 2013 and 2012, has been derived from Independent’s audited consolidated financial statements not appearing or incorporated by reference in this proxy statement/prospectus.

You should read the following financial information relating to Independent in conjunction with other information contained in this proxy statement/prospectus, including consolidated financial statements of Independent and related accompanying notes appearing in Independent’s Annual Report on Form 10-K most recently filed with the SEC and in the Quarterly Reports on Form 10-Q of Independent filed with the SEC after that Annual Report on Form 10-K was filed, if any, and in any Current Report on Form 8-K of Independent containing consolidated financial statements of Independent that was filed with the SEC after such Annual Report on Form 10-K, each of which reports is incorporated by reference in this proxy statement/prospectus. Independent’s historical results for any prior period are not necessarily indicative of results to be expected in any future period, and Independent’s historical results for the nine months ended September 30, 2017, are not necessarily indicative of its results to be expected for all of 2017. Independent has consummated several acquisitions in recent fiscal periods. The results and other financial information of those acquired operations are not included in the table below for the periods or dates prior to their respective acquisition dates and, therefore, the results for these prior periods are not comparable in all respects and may not be predictive of Independent’s future results. In addition, the selected financial information in the table immediately below does not include, on any basis, the results or financial condition of Integrity for any period or as of any date.

Reconciliations of Non-GAAP Financial Measures

The following information reconciles: (i) Independent’s tangible book value per common share, a non-GAAP financial measure, as of the dates presented to Independent’s book value per common share, a financial measure calculated and presented in accordance with GAAP, as of the dates presented; and (ii) its ratio of tangible common equity to tangible assets, a non-GAAP financial measure, as of the dates presented to Independent’s ratios of total common equity to total assets, a financial measure calculated and presented in accordance with GAAP, as of the dates presented.

Selected Financial Information of Integrity

The following selected historical consolidated financial information of Integrity as of and for the nine months ended September 30, 2017 and 2016, has been derived from Integrity’s unaudited financial statements, which Integrity’s management believes reflect all adjustments (consisting only of normal recurring adjustments) necessary for a fair presentation of its financial position and results of operations as of and for the periods ended on such dates, regulatory filings made by Integrity, and from other information provided by Integrity. The following selected historical consolidated financial information of Integrity as of and for each of the five years ended December 31, 2016, has been derived from Integrity’s audited financial statements, regulatory filings made by Integrity, and from other information provided by Integrity. You should read the following selected financial information relating to Integrity in conjunction with other information appearing elsewhere in this prospectus.