UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (date of earliest event reported): June 14, 2018

Tallgrass Energy GP, LP

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (913) 928-6060

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (17 CFR 230.405) or Rule 12b-2 of the Exchange Act (17 CFR 240.12b-2).

Emerging growth company  ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.  ☐

Legal Proceedings Regarding the Merger with Tallgrass Energy Partners, LP

As previously disclosed, on March 26, 2018, Tallgrass Energy GP, LP, a Delaware limited partnership (“TEGP”), Tallgrass Equity, LLC, a Delaware limited liability company (“Tallgrass Equity”), Tallgrass Energy Partners, LP, a Delaware limited partnership (“TEP”), Razor Merger Sub, LLC, a Delaware limited liability company and wholly owned subsidiary of TEP (“Merger Sub”), and Tallgrass MLP GP, LLC, a Delaware limited liability company (“TEP GP”), entered into a definitive Agreement and Plan of Merger (“Merger Agreement”). Subject to the satisfaction or waiver of certain conditions in the Merger Agreement, Merger Sub will merge with and into TEP, with TEP surviving the merger as a wholly owned subsidiary of Tallgrass Equity and its subsidiaries (the “Merger”). At the effective time of the Merger, each issued and outstanding common unit representing a limited partner interest in TEP (collectively, the “TEP Common Units”), except for any TEP Common Units held by Tallgrass Equity, Tallgrass Equity Investments, LLC, a wholly owned subsidiary of Tallgrass Equity, or TEP, will be converted into the right to receive 2.0 Class A shares representing limited partner interests in TEGP (collectively, the “TEGP Class A Shares”).

On May 18, 2018, TEP filed a definitive proxy statement (the “Proxy Statement”) with the Securities and Exchange Commission (“SEC”) for the solicitation of proxies in connection with the special meeting of TEP’s unitholders to be held on June 26, 2018 to consider and vote on a proposal to approve the Merger Agreement and the Merger.

As previously described in the Proxy Statement, in April 2018, two public common unitholders of TEP filed separate lawsuits under the federal securities laws in the United States District Court for the District of Delaware challenging the sufficiency of the disclosures made in the registration statement on Form S-4 filed by TEGP, of which the Proxy Statement forms a part, in connection with the Merger. These cases are captioned Leadford v. Tallgrass Energy Partners, LP, et al., Case No. 1:18-cv-00545-RGA (D. Del.) (the “Leadford Action”) and Dake v. Tallgrass Energy Partners, LP, et al., Case No. 1:18-cv-00580-RGA (D. Del.) (the “Dake Action”). The Leadford Action is asserted on behalf of a putative class of holders of TEP Common Units other than those held by Tallgrass Equity, Tallgrass Equity Investments, LLC or TEP, while the Dake Action is brought only on behalf of the named plaintiff.

Both actions allege violations of Sections 14(a) and 20(a) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and Rule 14a-9 promulgated thereunder based on various alleged omissions of material information from the registration statement on Form S-4 filed by TEGP, of which the Proxy Statement forms a part. The Leadford Action names as defendants TEP and each of TEP GP’s directors, individually. It seeks to compel TEP to issue revised disclosures, to enjoin the Merger, damages, and an award of costs and attorneys’ and experts’ fees. On April 24, 2018, the plaintiff in the Leadford Action filed a motion for preliminary injunction seeking to enjoin the TEP unitholder vote to approve the Merger. The Dake Action names as defendants TEP and each of TEP GP’s directors, individually. It seeks to enjoin the Merger (or, in the alternative, rescission or an award of rescissory damages in the event the Merger is completed), to compel TEP to issue revised disclosures, a declaration that the defendants violated Sections 14(a) and 20(a) of the Exchange Act and Rule 14a-9 promulgated thereunder, and an award of costs and attorneys’ and experts’ fees. On May 21, 2018, the plaintiff in the Dake Action filed a motion for a preliminary injunction seeking to enjoin the TEP unitholder vote to approve the Merger.

In order to moot what TEP considers to be unmeritorious disclosure claims, alleviate the costs, risks and uncertainties inherent in litigation and provide additional information to its unitholders, TEP has determined to voluntarily supplement the Proxy Statement as described in this Current Report on Form 8-K. Nothing in this Current Report on Form 8-K shall be deemed an admission of the legal necessity or materiality under applicable laws of any of the disclosures set forth herein. To the contrary, TEP specifically denies all allegations in the foregoing complaints, including without limitation that any additional disclosure was or is required. As a result of the supplemental disclosures set forth herein, plaintiffs in the Leadford Action and the Dake Action have agreed to withdraw their motions for a preliminary injunction.

SUPPLEMENT TO THE DEFINITIVE PROXY STATEMENT

TEP is providing additional information regarding the Proxy Statement to its unitholders. These disclosures should be read in connection with the Proxy Statement, which should be read in its entirety. To the extent that the information set forth herein differs from or updates information contained in the Proxy Statement, the information set forth herein shall supersede or supplement the information in the Proxy Statement. Defined terms used but not defined herein have the meanings set forth in the Proxy Statement. Without admitting in any way that the disclosures below are material or otherwise required by law, TEP makes the following amended and supplemental disclosures (with additional language in bold and underlined text below):

The disclosure in the list of peers under the heading “Peer Group Trading Analysis” on page 53 is hereby amended and supplemented by adding the trading multiples utilized by Evercore for each of the companies listed in the peer group across from the peer group company names:

The disclosure in the table on pages 54-55 is hereby amended and supplemented as follows:

Precedent M&A Transactions. FERC-regulated natural gas pipelines

The disclosure in the table on pages 56-57 is hereby amended and supplemented as follows:

Precedent M&A Transactions. Crude Oil Pipeline Transactions (Excluding Offshore Systems)

The disclosure in the second full paragraph on page 62 of the Proxy Statement is hereby supplemented by amending and restating the paragraph to read as follows:

Since January 2015, Evercore provided financial advisory services to (i) the TEP Conflicts Committee with respect to six separate dropdown transactions between TEP and Tallgrass Development and (ii) the TEGP Conflicts Committee with respect to one merger transaction between TE and Tallgrass Development, for which Evercore received a aggregate fees of $1.65 million and in addition to reimbursement of expenses.

Cautionary Note Concerning Forward-Looking Statements

Disclosures in this Current Report on Form 8-K contain forward-looking statements. All statements, other than statements of historical facts, included that address activities, events or developments that management expects, believes or anticipates will or may occur in the future are forward-looking statements. Such statements are subject to a number of assumptions, risks and uncertainties, many of which are beyond the control of TEP and TEGP, which may cause actual results to differ materially from those implied or expressed by the forward-looking statements, and other important factors that could cause actual results to differ materially from those projected, including those set forth in reports filed by TEP and TEGP with the SEC. Any forward-looking statement applies only as of the date on which such statement is made and TEP and TEGP do not intend to correct or update any forward-looking statement, whether as a result of new information, future events or otherwise, except as required by law.

Additional Information and Where to Find it

This communication may be deemed to be solicitation material in respect of the proposed transactions referred to in this Current Report on Form 8-K. In connection with the transactions referred to in this Current Report on Form 8-K, TEGP filed a registration statement on Form S-4 with the SEC that includes a preliminary proxy statement for the TEP unitholders. The registration statement was declared effective by the SEC on May 9, 2018, and TEP commenced mailing the definitive proxy statement/prospectus to its unitholders on or about May 23, 2018.

INVESTORS AND SECURITY HOLDERS OF TEGP AND TEP ARE URGED TO READ THE PROXY STATEMENT/PROSPECTUS, AS SUPPLEMENTED BY THIS CURRENT REPORT ON FORM 8-K, AND OTHER DOCUMENTS FILED WITH THE SEC CAREFULLY AND IN THEIR ENTIRETY WHEN THEY BECOME AVAILABLE BECAUSE THEY CONTAIN IMPORTANT INFORMATION.

Investors and security holders are able to obtain free copies of the proxy statement/prospectus and will be able to obtain free copies of other documents filed with the SEC by TEGP or TEP through the website maintained by the SEC at http://www.sec.gov. Copies of the documents filed with the SEC by TEGP and TEP will be available free of charge on TEGP’s and TEP’s website at www.tallgrassenergylp.com, in the “Investor Relations” tab near the top of the page, or by contacting TEGP’s and TEP’s Investor Relations Department at 913-928-6012.

Participants in the Solicitation

TEGP and TEP and their respective general partner’s directors and executive officers may be considered participants in the solicitation of proxies with respect to the proposed transactions under the rules of the SEC. Information about the directors and executive officers of TEGP’s general partner may be found in TEGP’s 2017 Form 10-K filed with the SEC on February 13, 2018, and any subsequent statements of changes in beneficial ownership filed with the SEC. Information about the directors and executive officers of TEP’s general partner may be found in TEP’s 2017 Form 10-K filed with the SEC on February 13, 2018, and any subsequent statements of changes in beneficial ownership filed with the SEC. These documents can be obtained free of charge from the sources indicated above. Additional information regarding the participants in the proxy solicitations and a description of their direct and indirect interests, by security holdings or otherwise, will also be included in any proxy statement and other relevant materials to be filed with the SEC when they become available.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Date: June 14, 2018