Form S-4/A CONCHO RESOURCES INC

SUMMARY

This summary highlights selected information included in this joint proxy statement/prospectus and does not contain all of the information that may be important to you. You should read this joint proxy statement/prospectus and its annexes carefully and in its entirety and the other documents to which Concho and RSP refer before you decide how to vote with respect to the proposals to be considered and voted on at the special meeting for your company. In addition, Concho and RSP incorporate by reference important business and financial information about Concho and RSP into this joint proxy statement/prospectus, as further described in the section entitled “Where You Can Find More Information” beginning on page 201. You may obtain the information incorporated by reference into this joint proxy statement/prospectus without charge by following the instructions in the section entitled “Where You Can Find More Information” beginning on page 201. Each item in this summary includes a page reference directing you to a more complete description of that item in this joint proxy statement/prospectus.

Information About the Companies (page 53)

Concho Resources Inc.

One Concho Center

600 West Illinois Avenue

Midland, Texas 79701

Phone: (432) 683-7443

Concho, whose legal name is Concho Resources Inc., was incorporated in Delaware in February 2006. Based in Midland, Texas, Concho is an independent oil and natural gas company engaged in the acquisition, development, exploration and production of oil and natural gas properties. Concho’s core operations are primarily focused in the Permian Basin of southeast New Mexico and West Texas. The Permian Basin is one of the most prolific oil and natural gas producing regions in the United States and is characterized by an extensive production history, long reserve life, multiple producing horizons and enhanced recovery potential. Currently, the majority of the rigs running in the Permian Basin are drilling horizontal wells. Concho’s legacy in the Permian Basin provides it with a deep understanding of operating and geological trends. Concho is actively developing its resource base by utilizing extended length lateral drilling, enhanced completion techniques, multi-well pad locations and large-scale development projects throughout its four core operating areas: the Northern Delaware Basin, the Southern Delaware Basin, the Midland Basin and the New Mexico Shelf.

RSP Permian, Inc.

3141 Hood Street, Suite 500

Dallas, Texas 75219

Phone: (214) 252-2700

RSP, whose legal name is RSP Permian, Inc., was incorporated in Delaware in September 2013. Based in Dallas, Texas, RSP is an independent oil and natural gas company engaged in the acquisition, exploration, exploitation, development and production of unconventional oil and associated liquids-rich natural gas reserves in the Permian Basin of West Texas. The vast majority of RSP’s acreage is located on large, contiguous acreage blocks in the core of the Midland Basin and the Delaware Basin, both sub-basins of the Permian Basin. The Midland Basin properties are primarily in the adjacent counties of Midland, Martin, Andrews, Ector, and Glasscock. The Delaware Basin properties are in Loving and Winkler counties.

Green Merger Sub Inc.

c/o Concho Resources Inc.

One Concho Center

600 West Illinois Avenue

Midland, Texas 79701

Phone: (432) 683-7443

Merger Sub, whose legal name is Green Merger Sub Inc., is a direct, wholly owned subsidiary of Concho. Upon the completion of the merger, Merger Sub will cease to exist. Merger Sub was incorporated in Delaware on March  23, 2018 for the sole purpose of effecting the merger.

The Merger and the Merger Agreement (page 123)

The terms and conditions of the merger are contained in the merger agreement, which is attached to this document as Annex A and is incorporated by reference herein in its entirety. Concho and RSP encourage you to read the merger agreement carefully and in its entirety, as it is the legal document that governs the merger.

The Concho board and RSP board each has unanimously approved the merger agreement and the transactions contemplated by the merger agreement. Pursuant to the terms and subject to the conditions included in the merger agreement, Concho has agreed to acquire RSP by means of a merger of Merger Sub with and into RSP, with RSP surviving the merger as a wholly owned subsidiary of Concho.

Merger Consideration (page 66)

As a result of the merger, each eligible share of RSP common stock issued and outstanding immediately prior to the effective time of the merger will be converted into the right to receive 0.320 of a share of Concho common stock (the merger consideration).

RSP stockholders will not be entitled to receive any fractional shares of Concho common stock in the merger, and no RSP stockholders will be entitled to dividends, voting rights or any other rights in respect of any fractional shares of Concho common stock. RSP stockholders that would have otherwise been entitled to receive a fractional share of Concho common stock will instead be entitled to receive, in lieu of fractional shares, an amount in cash, without interest, equal to the product of the volume weighted average price of Concho common stock for the five consecutive trading days immediately prior to the closing date as reported by Bloomberg, L.P., multiplied by the fraction of a share of Concho common stock to which the holder would otherwise be entitled.

Risk Factors (page 41)

The merger and an investment in Concho common stock involve risks, some of which are related to the transactions contemplated by the merger agreement. You should carefully consider the information about these risks set forth under the section entitled “Risk Factors” beginning on page 41, together with the other information included or incorporated by reference in this joint proxy statement/prospectus, particularly the risk factors contained in Concho’s and RSP’s Annual Reports on Form 10-K. RSP stockholders should carefully consider the risks set out in that section before deciding how to vote with respect to the merger proposal and non-binding compensation advisory proposal to be considered and voted on at the RSP special meeting, and Concho stockholders should carefully consider the risks set out in that section before deciding how to vote with respect to the Concho issuance proposal to be considered and voted on at the Concho special meeting. For additional information, see the section entitled “Where You Can Find More Information” beginning on page 201.

Treatment of RSP Equity Awards (page 115)

RSP Time-Based Restricted Stock

Immediately prior to the effective time of the merger, each outstanding award of shares of RSP time-based restricted stock granted under the RSP stock plan will automatically vest in full and any forfeiture restrictions applicable to such shares of RSP time-based restricted stock will lapse immediately. As a result, each share of RSP time-based restricted stock will be treated as and will have the same rights as a share of RSP common stock, including the right to receive the merger consideration, less applicable taxes required to be withheld.

RSP Performance-Based Restricted Stock

Immediately prior to the effective time of the merger, each outstanding award of shares of RSP performance-based restricted stock granted under the RSP stock plan will be deemed to have satisfied any continued service or time-based vesting requirements and have the applicable performance period end. RSP’s performance with respect to the performance goals applicable to such shares of RSP performance-based restricted stock will be calculated based on actual performance through the effective time of the merger, as reasonably determined by the compensation committee of the RSP board, in order to determine the number of shares of RSP performance-based restricted stock that will vest, and any forfeiture requirements applicable to such earned performance-based restricted stock will lapse immediately prior to the effective time of the merger. As a result, each share of earned performance-based restricted stock will be treated as and will have the same rights as a share of RSP common stock for purposes of the merger, including the right to receive the merger consideration, less applicable taxes required to be withheld.

Recommendation of the Concho Board of Directors and Reasons for the Merger (page 76)

The Concho board unanimously recommends that you vote “FOR” the Concho issuance proposal. For the factors considered by the Concho board in reaching this decision and additional information on the recommendation of the Concho board, see the section entitled “The Merger—Recommendation of the Concho Board of Directors and Reasons for the Merger” beginning on page 76.

Recommendation of the RSP Board of Directors and Reasons for the Merger (page 92)

The RSP board unanimously recommends that you vote “FOR” the merger proposal and “FOR” the non-binding compensation advisory proposal. For the factors considered by the RSP board in reaching this decision and additional information on the recommendation of the RSP board, see the section entitled “The Merger—Recommendation of the RSP Board of Directors and Reasons for the Merger” beginning on page  92.

Opinions of Financial Advisors (pages 80 and 96)

Opinion of Morgan Stanley, Concho’s financial advisor

Concho retained Morgan Stanley & Co. LLC (which we refer to as “Morgan Stanley”) as its exclusive financial advisor in connection with the transactions contemplated by the merger agreement. Morgan Stanley delivered its oral opinion to the Concho board on March 27, 2018, which opinion was subsequently confirmed in a written opinion dated March 27, 2018, that, as of the date of such opinion, and subject to the various assumptions made, procedures followed, matters considered, and qualifications and limitations on the scope of the review undertaken by Morgan Stanley as set forth in its written opinion, the exchange ratio pursuant to the merger agreement was fair from a financial point of view to Concho.

The full text of Morgan Stanley’s written opinion, dated March 27, 2018, which sets forth assumptions made, procedures followed, matters considered and limitations on the review undertaken in connection with the

opinion, is attached as Annex B to this joint proxy statement/prospectus and is incorporated by reference herein in its entirety. Concho stockholders should read Morgan Stanley’s opinion carefully and in its entirety for a discussion of the assumptions made, procedures followed, matters considered and qualifications and limitations on the scope of the review undertaken by Morgan Stanley in rendering its opinion. This summary is qualified in its entirety by reference to the full text of such opinion. Morgan Stanley’s opinion was directed to the Concho board, in its capacity as such, and addressed only the fairness from a financial point of view to Concho of the exchange ratio pursuant to the merger agreement as of the date of such opinion. Morgan Stanley’s opinion did not address any other aspects or implications of the merger. Morgan Stanley’s opinion did not in any manner address the price at which the Concho common stock would trade following the consummation of the merger or at any time, and Morgan Stanley expressed no opinion or recommendation to any holder of shares of Concho common stock or RSP common stock as to how such holder should vote at the Concho special meeting or the RSP special meeting, respectively, or whether to take any other action with respect to the merger.

For additional information, see the section entitled “The Merger—Opinion of Morgan Stanley, Concho’s Financial Advisor” beginning on page 80 and Annex B.

Opinion of TPH, RSP’s financial advisor

RSP retained Tudor Pickering Holt & Co Advisors LP (which we refer to as “TPH”) as its exclusive financial advisor in connection with a potential strategic transaction with Concho and other strategic alternatives. On March 27, 2018, TPH rendered to the RSP board its oral opinion, which was subsequently confirmed by delivery of a written opinion dated March 27, 2018, that, based upon and subject to the limitations, qualifications and assumptions set forth in its opinion, as of the date of the opinion, the merger consideration to be received by the holders of eligible shares of RSP common stock pursuant to the merger agreement was fair, from a financial point of view, to such stockholders.

The full text of TPH’s written opinion, dated March 27, 2018, which describes, among other things, the assumptions made, procedures followed, factors considered and qualifications and limitations on the review undertaken, is attached as Annex C to this joint proxy statement/prospectus and is incorporated by reference in its entirety. The summary of TPH’s opinion set forth in this joint proxy statement/prospectus is qualified in its entirety by reference to the full text of the opinion. RSP stockholders are urged to read the TPH opinion carefully and in its entirety. TPH delivered its opinion for the information and assistance of the RSP board in connection with its evaluation of the merger. The opinion speaks only as of the date and time it was rendered and not as of the time of the transactions contemplated by the merger agreement or any other time. The TPH opinion is not a recommendation as to how any holder of shares of RSP common stock should vote with respect to the merger proposal or the non-binding compensation advisory proposal.

For additional information, see the section entitled “The Merger—Opinion of TPH, RSP’s Financial Advisor” beginning on page  96 and Annex C.

Special Meeting of Concho Stockholders (page 54)

Date, Time, Place and Purpose of the Concho Special Meeting

The Concho special meeting will be held on July 17, 2018, at 10 a.m., Central Time, at One Concho Center, 600 West Illinois Avenue, Midland, Texas 79701. The purpose of the Concho special meeting is to consider and vote on the Concho issuance proposal. Approval of the Concho issuance proposal is a condition to the obligation of Concho and RSP to complete the merger.

Record Date and Outstanding Shares of Concho Common Stock

Only holders of record of issued and outstanding shares of Concho common stock as of the close of business on June 1, 2018, the record date for the Concho special meeting, are entitled to notice of, and to vote at, the Concho special meeting or any adjournment or postponement of the Concho special meeting.

As of the close of business on the record date, there were 149,069,231 shares of Concho common stock issued and outstanding and entitled to vote at the Concho special meeting. You may cast one vote for each share of Concho common stock that you held as of the close of business on the record date.

A complete list of Concho stockholders entitled to vote at the Concho special meeting will be available for inspection at Concho’s principal place of business during regular business hours for a period of no less than 10 days before the Concho special meeting and during the Concho special meeting at One Concho Center, 600 West Illinois Avenue, Midland, Texas 79701.

Quorum; Abstentions and Broker Non-Votes

A quorum of Concho stockholders is necessary for Concho to hold a valid meeting. The presence at the Concho special meeting, in person or by proxy, of the holders of a majority of the outstanding shares of Concho common stock entitled to vote at the Concho special meeting constitutes a quorum.

If you submit a properly executed proxy card, even if you do not vote for the proposal or vote to “abstain” in respect of the proposal, your shares of Concho common stock will be counted for purposes of calculating whether a quorum is present for the transaction of business at the Concho special meeting. Concho common stock held in “street name” with respect to which the beneficial owner fails to give voting instructions to the broker, bank or other nominee, and Concho common stock with respect to which the beneficial owner otherwise fails to vote, will not be considered present and entitled to vote at the Concho special meeting for the purpose of determining the presence of a quorum.

A broker non-vote will result if your broker, bank or other nominee returns a proxy but does not provide instruction as to how shares should be voted on a particular matter. It is not expected that there will be any broker non-votes at the Concho special meeting. However, if there are any broker non-votes, the shares will not be considered present and entitled to vote at the Concho special meeting for the purpose of determining the presence of a quorum.

Executed but unvoted proxies will be voted in accordance with the recommendation of the Concho board.

Required Vote to Approve the Concho Issuance Proposal

Approval of the Concho issuance proposal requires the affirmative vote of a majority of votes cast by Concho stockholders entitled to vote on the proposal. Abstentions will have the same effect as a vote “AGAINST” the proposal, and broker non-votes will have no effect on the outcome of the vote.

The Concho issuance proposal is described in the section entitled “Concho Proposal” beginning on page 59.

Voting by Directors and Executive Officers

As of May 31, 2018, Concho directors and executive officers, and their affiliates, as a group, owned and were entitled to vote 1,700,926 shares of Concho common stock, or approximately 1.1% of the total outstanding shares of Concho common stock as of May 31, 2018.

Concho currently expects that all of its directors and executive officers will vote their shares “FOR” the Concho issuance proposal.

Adjournment

If a quorum is not present or if there are not sufficient votes for the approval of the Concho issuance proposal, Concho expects that the Concho special meeting will be adjourned by the chairman of the Concho special meeting to solicit additional proxies in accordance with the merger agreement. At any subsequent reconvening of the Concho special meeting, all proxies will be voted in the same manner as the manner in which such proxies would have been voted at the original convening of the Concho special meeting, except for any proxies that have been validly revoked or withdrawn prior to the subsequent meeting.

Special Meeting of RSP Stockholders (page 60)

Date, Time, Place and Purpose of the RSP Special Meeting

The RSP special meeting will be held on July 17, 2018, at 10 a.m., Central Time, at 3141 Hood Street, Suite 700, Dallas, Texas 75219. The purpose of the RSP special meeting is to consider and vote on the merger proposal and the non-binding compensation advisory proposal. Approval of the merger proposal is a condition to the obligation of RSP and Concho to complete the merger. Approval of the non-binding compensation advisory proposal is not a condition to the obligation of either RSP or Concho to complete the merger.

Record Date and Outstanding Shares of RSP Common Stock

Only holders of record of issued and outstanding shares of RSP common stock as of the close of business on June 1, 2018, the record date for the RSP special meeting, are entitled to notice of, and to vote at, the RSP special meeting or any adjournment or postponement of the RSP special meeting.

As of the close of business on the record date, there were 159,422,610 shares of RSP common stock issued and outstanding and entitled to vote at the RSP special meeting. You may cast one vote for each share of RSP common stock that you held as of the close of business on the record date.

A complete list of RSP stockholders entitled to vote at the Concho special meeting will be available for inspection at RSP’s principal place of business during regular business hours for a period of no less than 10 days before the RSP special meeting and during the RSP special meeting at 3141 Hood Street, Suite 700, Dallas, Texas 75219.

Quorum; Abstentions and Broker Non-Votes

A quorum of RSP stockholders is necessary for RSP to hold a valid meeting. The presence at the RSP special meeting, in person or by proxy, of the holders of a majority of the outstanding shares of RSP common stock entitled to vote at the RSP special meeting constitutes a quorum.

If you submit a properly executed proxy card, even if you do not vote for the proposal or vote to “abstain” in respect of the proposal, your shares of RSP common stock will be counted for purposes of calculating whether a quorum is present for the transaction of business at the RSP special meeting. RSP common stock held in “street name” with respect to which the beneficial owner fails to give voting instructions to the broker, bank or other nominee, and RSP common stock with respect to which the beneficial owner otherwise fails to vote, will not be considered present and entitled to vote at the RSP special meeting for the purpose of determining the presence of a quorum.

A broker non-vote will result if your broker, bank or other nominee returns a proxy but does not provide instruction as to how shares should be voted on a particular matter. It is not expected that there will be any broker non-votes at the RSP special meeting. However, if there are any broker non-votes, the shares will not be considered present and entitled to vote at the RSP special meeting for the purpose of determining the presence of a quorum.

Executed but unvoted proxies will be voted in accordance with the recommendations of the RSP board.

Required Vote to Approve the Merger Proposal

Approval of the merger proposal requires the affirmative vote of a majority of the outstanding shares of RSP common stock entitled to vote on the proposal. Abstentions and broker non-votes will have the same effect as a vote “AGAINST” the merger proposal. Failure to vote on the merger proposal will have the same effect as a vote “AGAINST” the merger proposal.

The merger proposal is described in the section entitled “RSP Proposals” beginning on page 65.

Required Vote to Approve the Non-Binding Compensation Advisory Proposal

Approval of the non-binding compensation advisory proposal requires the affirmative vote of a majority of the shares of RSP common stock present in person or represented by proxy at the RSP special meeting and entitled to vote on the proposal. Abstentions will have the same effect as a vote “AGAINST” the proposal, and broker non-votes will have no effect on the outcome of the vote.

The non-binding compensation advisory proposal is described in the section entitled “RSP Proposals” beginning on page 65.

Voting by Directors and Executive Officers

As of May 31, 2018, RSP directors and executive officers, and their affiliates, as a group, owned and were entitled to vote 13,395,685 shares of RSP common stock, or approximately 8.4% of the total outstanding shares of RSP common stock as of May 31, 2018.

RSP currently expects that all of its directors and executive officers will vote their shares “FOR” the merger proposal and “FOR” the non-binding compensation advisory proposal.

Adjournment

If a quorum is not present or if there are not sufficient votes for the approval of the merger proposal, RSP expects that the RSP special meeting will be adjourned by the chairman of the RSP special meeting to solicit additional proxies in accordance with the merger agreement. At any subsequent reconvening of the RSP special meeting, all proxies will be voted in the same manner as the manner in which such proxies would have been voted at the original convening of the RSP special meeting, except for any proxies that have been validly revoked or withdrawn prior to the subsequent meeting.

Interests of Concho Directors and Executive Officers in the Merger (page 114)

In considering the recommendation of the Concho board with respect to the Concho issuance proposal, Concho stockholders should be aware that the executive officers and directors of Concho have interests in the merger that may be different from, or in addition to, the interests of Concho stockholders generally. These interests are described in more detail in the section entitled “The Merger—Interests of Concho Directors and Executive Officers in the Merger” beginning on page 114. The members of the Concho board were aware of and

considered these interests, among other matters, in evaluating and negotiating the merger agreement, in approving the merger agreement and in determining to recommend that Concho stockholders approve the Concho issuance proposal.

Board of Directors and Management of Concho Following Completion of the Merger (page 114)

Under the terms of the merger agreement, Concho has agreed to take all necessary corporate action so that upon and after the effective time of the merger, the size of the Concho board is increased by one member, and prior to the completion of the merger, one member of the RSP board determined to be independent by the Concho board and to be mutually agreed between RSP and Concho is appointed to the Concho board to fill the vacancy on the Concho board created by such increase. Concho, through the Concho board, has agreed to take all necessary action to nominate such new director for election to the Concho board in the proxy statement relating to the first annual meeting of the stockholders of Concho following the completion of the merger.

On May 17, 2018, pursuant to the terms of the merger agreement and in accordance with the Concho certificate of incorporation and Concho bylaws, the Concho board increased the size of the Concho board by one member (which we refer to as the “board size increase”). In addition, the Concho board appointed Steven Gray, the current Chief Executive Officer of RSP, who had been unanimously recommended by the RSP board, to fill the vacancy created by the board size increase. Mr. Gray will serve as a Class III director of Concho until the next annual meeting of stockholders of Concho in which Class III directors are elected. Both the board size increase and appointment of Mr. Gray to the Concho board are effective as of, and contingent upon the occurrence of, the effective time of the merger.

Upon completion of the merger, the current directors and executive officers of Concho are expected to continue in their current positions, other than as may be publicly announced by Concho in the normal course.

Interests of RSP Directors and Executive Officers in the Merger (page 115)

In considering the recommendation of the RSP board with respect to the merger proposal and the non-binding compensation advisory proposal, RSP stockholders should be aware that the executive officers and directors of RSP have interests in the merger that may be different from, or in addition to, the interests of RSP stockholders generally. These interests include, but are not limited to, the treatment in the merger of awards of RSP time-based restricted stock and RSP performance-based restricted stock held by RSP directors and executive officers, potential benefits upon a qualifying termination of employment in connection with the merger and rights to ongoing indemnification and insurance coverage.

These interests are described in more detail in the sections entitled “The Merger—Interests of RSP Directors and Executive Officers in the Merger,” “The Merger—Treatment of RSP Equity Awards,” “The Merger—Executive Officer Severance Arrangements” and “The Merger—Merger-Related Compensation” beginning on pages 115, 115, 117 and 118, respectively.

The members of the RSP board were aware of and considered these interests, among other matters, in evaluating and negotiating the merger agreement, in approving the merger agreement and in determining to recommend that RSP stockholders approve the merger proposal.

Conditions to the Completion of the Merger (page 152)

Each party’s obligation to complete the merger is subject to the satisfaction or waiver of the following mutual conditions:

The obligations of Concho and Merger Sub to complete the merger are subject to the satisfaction or waiver of further conditions, including:

The obligation of RSP to complete the merger is subject to the satisfaction or waiver of the following additional conditions:

No Solicitation (page 135)

No Solicitation by Concho

Concho has agreed that, from and after March 27, 2018, Concho and its officers and directors will not, will cause Concho’s subsidiaries and their respective officers and directors not to, and will use their reasonable best efforts to cause the other representatives of Concho and its subsidiaries not to, directly or indirectly, initiate, solicit any inquiry or propose the making of any proposal or offer that constitutes, or would reasonably be expected to result in, a Concho competing proposal (as such term is defined in the section entitled “The Merger Agreement—No Solicitation; Changes of Recommendation—Definitions of Competing Proposals” beginning on page 141).

No Solicitation by RSP

RSP has agreed that, from and after March 27, 2018, RSP and its officers and directors will, will cause RSP’s subsidiaries and their respective officers and directors to, and will use their reasonable best efforts to cause the other representatives of RSP and its subsidiaries to, immediately cease, and cause to be terminated, any discussion or negotiations ongoing with any third party with respect to any inquiry, proposal or offer that constitutes, or would reasonably be expected to lead to, a RSP competing proposal (as such term is defined in the section entitled “The Merger Agreement—No Solicitation; Changes of Recommendation—Definitions of Competing Proposals” beginning on page 141).

RSP has also agreed that, from and after March 27, 2018, RSP and its officers and directors will not, will cause RSP’s subsidiaries and their respective officers and directors not to, and will use their reasonable best efforts to cause the other representatives of RSP and its subsidiaries not to:

Notwithstanding the agreements described above, prior to, but not after, the time the merger proposal has been approved by RSP stockholders, RSP may engage in the second and third bullets directly above with any person if (i) RSP receives a bona fide written RSP competing proposal from such person that was not solicited at any time following March 27, 2018; and (ii) such RSP competing proposal did not arise from a breach of the obligations described directly above and in the section entitled “The Merger Agreement—No Solicitation; Changes of Recommendation—Definitions of Competing Proposals” beginning on page 141; provided, however, that:

Notwithstanding the above restrictions, RSP may, (i) in response to an unsolicited inquiry or proposal, seek to clarify the terms and conditions of such inquiry or proposal to determine whether such inquiry or proposal constitutes a RSP superior proposal and (ii) in response to an inquiry or proposal from a third party, inform a third party or its representative of the “no solicitation” obligations described above (without conveying, requesting or attempting to gather any other information except as otherwise specifically permitted under the merger agreement).

Changes of Recommendation (page 135)

Concho Restrictions on Changes of Recommendation

Subject to certain exceptions described below, the Concho board may not effect a Concho recommendation change (as defined in the section entitled “The Merger Agreement—No Solicitation; Changes of Recommendation—Concho: Restrictions on Changes of Recommendation” beginning on page 138).

RSP Restrictions on Changes of Recommendation

Subject to certain exceptions described below, the RSP board may not effect a RSP recommendation change (as defined in the section entitled “The Merger Agreement—No-Solicitation; Changes of Recommendation—RSP: Restrictions on Changes of Recommendation” beginning on page 138).

Concho: Permitted Changes of Recommendation in Connection with Intervening Events

At any time prior to, but not after, the time that the Concho issuance proposal has been approved by Concho stockholders, if a Concho intervening event (as defined in the section entitled “The Merger Agreement—No Solicitation; Changes of Recommendation—Concho: Permitted Changes of Recommendation in Connection with Intervening Events” beginning on page 139) occurs, Concho may effect a Concho recommendation change if:

RSP: Permitted Changes of Recommendation and Permitted Termination to Enter into a Superior Proposal

Prior to, but not after, the merger proposal has been approved by RSP stockholders, in response to a bona fide written RSP competing proposal from a third party that was not solicited at any time following March 27, 2018 and did not arise from a breach of the “no solicitation” obligations described above and in the section entitled “The Merger Agreement—No Solicitation; Changes of Recommendation—No Solicitation by RSP,” the RSP board may effect a RSP recommendation change or terminate the merger agreement if:

RSP: Permitted Changes of Recommendation in Connection with Intervening Events

Prior to, but not after, the time the merger proposal has been approved by RSP stockholders, in response to a RSP intervening event (as defined in the section entitled “The Merger Agreement—No Solicitation; Changes of Recommendation—RSP: Permitted Changes of Recommendation in Connection with Intervening Events” beginning on page 140) that occurs or arises after March 27, 2018 and that did not arise from or in connection with a breach of the merger agreement by RSP, RSP may effect a RSP recommendation change if:

Termination (page 155)

Concho and RSP may terminate the merger agreement and abandon the merger at any time prior to the effective time of the merger by mutual written consent of Concho and RSP.

The merger agreement may also be terminated by either Concho or RSP at any time prior to the effective time of the merger in any of the following situations:

In addition, the merger agreement may be terminated by Concho:

Further, the merger agreement may be terminated by RSP:

Termination Fees (page 156)

Termination Fees Payable by Concho

The merger agreement requires Concho to pay RSP a termination fee of $350 million (which we refer to as the “reverse termination fee”) if:

In no event will Concho be required to pay the reverse termination fee on more than one occasion.

Termination Fees Payable by RSP

The merger agreement requires RSP to pay Concho a termination fee of $250 million (which we refer to as the “termination fee”) if:

In no event will RSP be required to pay the termination fee on more than one occasion.

Regulatory Approvals (page 114)

The completion of the merger is subject to the receipt of antitrust clearance in the United States. Under the HSR Act, and the rules promulgated thereunder, the merger may not be completed until notification and report forms have been filed with the Federal Trade Commission (which we refer to as the “FTC”) and the Department of Justice (which we refer to as the “DOJ”) and the applicable waiting period (or any extension of such waiting period) has expired or been terminated.

On April 27, 2018, Concho and RSP received notice of early termination of the applicable waiting period under the HSR Act.

Neither Concho nor RSP is aware of any material governmental approvals or actions that are required for completion of the merger other than as described above. It is presently contemplated that if any such additional material governmental approvals or actions are required, those approvals or actions will be sought.

For additional information, see the section entitled “The Merger Agreement—HSR and Other Regulatory Approvals” beginning on page 146.

Specific Performance; Remedies (page 158)

Concho, RSP and Merger Sub have agreed that each will be entitled to an injunction or injunctions, or any other appropriate form of specific performance or equitable relief, to prevent breaches of the merger agreement and to enforce specifically the terms and provisions of the merger agreement.

Except in the case of fraud or a willful and material breach, the monetary remedies and the specific performance remedies set forth in the merger agreement will be the receiving party’s sole and exclusive remedy against the paying party.

No Dissenters’ or Appraisal Rights (page 188)

No dissenters’ or appraisal rights will be available with respect to the transactions contemplated by the merger agreement.

Material U.S. Federal Income Tax Consequences of the Merger (page 160)

It is a condition to RSP’s and Concho’s respective obligation to complete the merger that each receive a written opinion from its respective counsel to the effect that, on the basis of facts, representations and assumptions set forth or referred to in such opinions, for U.S. federal income tax purposes, the merger will qualify as a reorganization within the meaning of Section 368(a) of the Internal Revenue Code.

Assuming the merger qualifies as a reorganization U.S. holders of shares of RSP common stock generally will not recognize any gain or upon receipt of Concho common stock in exchange for RSP common stock in the merger, except that gain or loss will be recognized with respect to any cash received in lieu of a fractional share of Concho common stock. The U.S. federal income tax consequences of the merger are discussed in more detail in the section entitled “Material U.S. Federal Income Tax Consequences of the Merger” beginning on page 160. The discussion of the material U.S. federal income tax consequences contained in this joint proxy statement/prospectus is intended to provide only a general discussion and is not a complete analysis or description of all potential U.S. federal income tax consequences of the merger that may vary with, or are dependent on, individual circumstances. In addition, it does not address the effects of any foreign, state or local tax laws.

TAX MATTERS ARE COMPLICATED AND THE TAX CONSEQUENCES OF THE MERGER WILL DEPEND ON THE FACTS OF YOUR OWN SITUATION. YOU SHOULD CONSULT YOUR OWN TAX ADVISOR AS TO THE SPECIFIC TAX CONSEQUENCES AS A RESULT OF THE MERGER TO YOU IN YOUR PARTICULAR CIRCUMSTANCES.

Litigation Relating to the Merger (page 121)

Following the public announcement of the merger, three putative shareholder class action lawsuits were filed against RSP, the members of the RSP board, and in two lawsuits, Concho and Merger Sub. All three actions were filed in the United States District Court for the Northern District of Texas. Among other remedies, the plaintiffs seek to enjoin the transactions contemplated by the merger agreement. The defendants have not yet answered or otherwise responded to the complaints.

For additional information, see the section entitled “Litigation Relating to the Merger” beginning on page 121.

Comparison of Stockholders’ Rights (page 177)

The rights of RSP stockholders who receive shares of Concho common stock in the merger will be governed by the Restated Certificate of Incorporation of Concho (which we refer to as the “Concho certificate of incorporation”) and the Fourth Amended and Restated Bylaws of Concho (which we refer to as the “Concho bylaws”), rather than by the Amended and Restated Certificate of Incorporation of RSP (which we refer to as the “RSP certificate of incorporation”) and the Amended and Restated Bylaws of RSP (which we refer to as the “RSP bylaws”). As a result, RSP stockholders will have different rights once they become Concho stockholders due to the differences in the organizational documents of RSP and Concho. The key differences are described in the section entitled “Comparison of Stockholders’ Rights” beginning on page 177.

Listing of Concho Common Stock; Delisting and Deregistration of RSP Shares (page 120)

If the merger is completed, the shares of Concho common stock to be issued in the merger will be listed for trading on the NYSE, shares of RSP common stock will be delisted from the NYSE and deregistered under the Exchange Act, and RSP will no longer be required to file periodic reports with the SEC pursuant to the Exchange Act.

SELECTED HISTORICAL CONSOLIDATED FINANCIAL DATA OF CONCHO

The following table presents selected historical consolidated financial data for Concho (1) as of and for the years ended December 31, 2017, 2016, 2015, 2014 and 2013 and (2) as of and for the three months ended March 31, 2018 and 2017. The consolidated financial data for each of the years ended December 31, 2017, 2016 and 2015, and as of December 31, 2017 and 2016 have been derived from Concho’s selected financial data and audited consolidated financial statements included in its Annual Report on Form 10-K for the fiscal year ended December 31, 2017, as amended, and its Quarterly Report on Form 10-Q for the quarter ended March 31, 2018, each of which is incorporated by reference herein in its entirety. The selected historical consolidated financial data of Concho for each of the years ended December 31, 2014 and 2013 and as of December 31, 2015, 2014 and 2013 have been derived from Concho’s selected financial data and audited consolidated financial statements for such years, which have not been incorporated by reference herein. The selected historical consolidated financial data for the three months ended March 31, 2018 and 2017 and as of March 31, 2018 have been derived from Concho’s unaudited consolidated financial data included in its Quarterly Report on Form 10-Q for the quarter ended March 31, 2018, which is incorporated by reference herein in its entirety. This selected balance sheet data as of March 31, 2017 has been derived from Concho’s unaudited consolidated financial statements as of March 31, 2017, which have not been incorporated by reference herein.

The information set forth below is only a summary and is not necessarily indicative of the results of future operations of Concho nor does it include the effects of the merger. This summary should be read together with the other information contained in Concho’s Annual Report on Form 10-K for the fiscal year ended December 31, 2017 and Quarterly Report on Form 10-Q for the quarter ended March 31, 2018, including the sections entitled “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and the consolidated financial statements and related notes therein. For additional information, see the section entitled “Where You Can Find More Information” beginning on page 201.

Non-GAAP Financial Measures

Reconciliation of Net Income (Loss) to EBITDAX

EBITDAX (as defined below) is presented in the Selected Historical Consolidated Financial Data of Concho and reconciled from the GAAP measure of net income (loss) because of its wide acceptance by the investment community as a financial indicator.

For purposes of the Selected Historical Consolidated Financial Data of Concho, EBITDAX is defined as net income (loss), plus (1) exploration and abandonments, (2) depreciation, depletion and amortization, (3) accretion of discount on asset retirement obligations, (4) impairments of long-lived assets, (5) non-cash stock-based compensation, (6) (gain) loss on derivatives, (7) net cash receipts from (payments on) derivatives, (8) (gain) loss on disposition of assets, net, (9) interest expense, (10) loss on extinguishment of debt, (11) gain on equity method investment distribution, (12) federal and state income tax expense (benefit) from continuing operations and (13) similar items listed above that are presented in discontinued operations. EBITDAX is not a measure of net income (loss) or cash flows as determined by GAAP.

EBITDAX provides additional information that may be used to better understand Concho’s operations. EBITDAX is one of several metrics that Concho uses as a supplemental financial measurement in the evaluation of its business and should not be considered as an alternative to, or more meaningful than, net income (loss) as an

indicator of operating performance. Certain items excluded from EBITDAX are significant components in understanding and assessing a company’s financial performance, such as a company’s cost of capital and tax structure, as well as the historic cost of depreciable and depletable assets. EBITDAX, as used by Concho, may not be comparable to similarly titled measures reported by other companies. Concho believes that EBITDAX is a widely followed measure of operating performance and is one of many metrics used by Concho management team and by other users of Concho consolidated financial statements. For example, EBITDAX can be used to assess Concho’s operating performance and return on capital in comparison to other independent exploration and production companies without regard to financial or capital structure and to assess the financial performance of Concho’s assets and the company without regard to capital structure or historical cost basis.

The following table provides a reconciliation of the GAAP measure of net income (loss) to EBITDAX (non-GAAP) for the periods indicated:

SELECTED HISTORICAL CONSOLIDATED FINANCIAL DATA OF RSP

The following table sets forth RSP’s selected consolidated historical financial information that has been derived from RSP’s consolidated financial statements (1) as of and for the years ended December 31, 2017, 2016, 2015, 2014 and 2013 and (2) as of and for the three months ended March 31, 2018 and 2017. The information set forth below is only a summary and is not necessarily indicative of the results of future operations of RSP nor does it include the effects of the merger. You should read this financial information together with RSP’s consolidated financial statements, the related notes and the sections entitled “Management’s Discussion and Analysis of Financial Condition and Results of Operations” in its Annual Report on Form 10-K for the year ended December 31, 2017 filed on February 27, 2018, as amended, and Quarterly Report on Form 10-Q for the quarter ended March 31, 2018 filed on May 2, 2018, each of which is incorporated into this joint proxy statement/prospectus by reference. The selected statement of operations data and cash flow data for the years ended December 31, 2014 and 2013, and selected balance sheet data as of December 31, 2015, 2014 and 2013 have been derived from RSP’s audited consolidated financial statements for such years, which have not been incorporated into this joint proxy statement/prospectus by reference. The selected historical consolidated financial data for the three months ended March 31, 2018 and 2017 and as of March 31, 2018 have been derived from RSP’s unaudited consolidated financial data included in its Quarterly Report on Form 10-Q for the quarter ended March 31, 2018, which is incorporated into this joint proxy statement/prospectus by reference. This selected balance sheet data as of March 31, 2017 has been derived from RSP’s unaudited consolidated financial statements as of March 31, 2017, which have not been incorporated by reference herein. For additional information, see the section titled “Where You Can Find More Information” beginning on page 201.