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 12, 2013

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:

On June 12, 2013, Consumers Energy Company (“Consumers”) filed, with the Michigan Public Service Commission (“MPSC”), a petition to close the docket or in the alternative, suspend and indefinitely extend the schedule in its present natural gas rate case. Overall non-fuel costs for 2013 are forecast to be lower than anticipated when Consumers originally filed the case. Consumers plans to file a new and amended case containing more recent historical data and an updated projected test year, primarily for rate relief associated with projected capital expenditures.

CMS Energy Corporation reaffirmed its guidance for 2013 adjusted earnings of $1.63 to $1.66 per share.

For more information and to obtain a copy of the petition please visit the MPSC’s website at: http://efile.mpsc.state.mi.us/efile/viewcase.php?casenum=17197.

In accordance with General Instruction B.2 of Form 8-K, the information in this Current Report on Form 8-K shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, except as shall be expressly set forth in such a filing.

CMS Energy Corporation provides financial results on both a reported (Generally Accepted Accounting Principles (“GAAP”)) and adjusted (non-GAAP) basis. Management views adjusted earnings as a key measure of the company’s present operating financial performance, unaffected by discontinued operations, asset sales, impairments, regulatory items from prior years, or other items detailed in the attached summary financial statements. Certain of these items have the potential to impact, favorably or unfavorably, the company’s reported earnings in 2013. The company is not able to estimate the impact of these matters and is not providing reported earnings guidance.

This Form 8-K contains “forward-looking statements” as defined in Rule 3b-6 of the Securities Exchange Act of 1934, as amended, Rule 175 of the Securities Act of 1933, as amended, and relevant legal decisions. The forward-looking statements are subject to risks and uncertainties. They should be read in conjunction with “FORWARD-LOOKING STATEMENTS AND INFORMATION” and “RISK FACTORS” sections of CMS Energy Corporation’s Form 10-K and Consumers Energy Company’s Form 10-K each for the Year Ended December 31, 2012 and as updated in CMS Energy Corporation’s and Consumers Energy Company’s Forms 10-Q for the Quarter Ended March 31, 2013. CMS Energy Corporation’s and Consumers Energy Company’s “FORWARD-LOOKING STATEMENTS AND INFORMATION” and “RISK FACTORS” sections are incorporated herein by reference and discuss important factors that could cause CMS Energy Corporation’s and Consumers Energy Company’s results to differ materially from those anticipated in such statements.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrants have duly caused this report to be signed on their behalf by the undersigned hereunto duly authorized.