UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 12b-25

NOTIFICATION OF LATE FILING

If the notification relates to a portion of the filing checked above, identify the Item(s) to which the notification relates:

PART I — REGISTRANT INFORMATION

Energy Future Holdings Corp.

(Full Name of Registrant)

(Former Name if Applicable)

Energy Plaza, 1601 Bryan Street

(Address of Principal Executive Office (Street and Number))

Dallas, Texas 75201

(City, State and Zip Code)

PART II — RULES 12b-25(b) AND (c)

If the subject report could not be filed without unreasonable effort or expense and the registrant seeks relief pursuant to Rule 12b-25(b), the following should be completed. (Check box if appropriate)

PART III — NARRATIVE

State below in reasonable detail why Forms 10-K, 20-F, 11-K, 10-Q, 10-D, N-SAR, N-CSR, or the transition report or portion thereof, could not be filed within the prescribed time period.

(Attach extra sheets if needed)

Energy Future Holdings Corp. (“EFH Corp.”), Energy Future Competitive Holdings Company LLC (“EFCH”), Texas Competitive Electric Holdings Company LLC (“TCEH”), and Energy Future Intermediate Holding Company LLC (“EFIH” and together with EFH Corp., EFCH and TCEH, the “Companies”), principals of EFH Corp.’s existing equity holders and certain unaffiliated holders of claims against the Companies and certain of their subsidiaries, together with professional advisors to such parties, are engaging in discussions regarding the terms and conditions to various restructuring alternatives to facilitate the creation of a sustainable capital structure for the Companies.

Given the constructive nature of these ongoing discussions, TCEH has elected not to make certain interest payments due April 1, 2014 and to use the permitted grace periods as provided in the applicable debt agreements. TCEH’s decision of how much of the applicable grace periods to use before pursuing any restructuring alternative will be evaluated based on various factors, including the status of the discussions described herein. There is no guarantee that these discussions will result in an agreement.

In consideration of liquidity issues affecting EFH Corp. and its subsidiaries (other than Oncor Electric Delivery Holdings Company LLC and its subsidiaries) and TCEH’s anticipated inability to repay debt obligations due in 2014, it is expected that the reports of the independent registered public accounting firm that accompany the audited consolidated financial statements for the year ended December 31, 2013 included in the Annual Reports on Form 10-K for the year ended December 31, 2013 to be filed by EFH Corp., EFCH and EFIH will each contain an explanatory paragraph regarding substantial doubt about the applicable registrant’s ability to continue as a going concern. The Credit Agreement, dated October 10, 2007, by and among TCEH, as borrower, EFCH and certain of TCEH’s subsidiaries, as guarantors, and the members of the lending syndicate and certain other agents (as amended, modified or otherwise supplemented, the “TCEH Credit Agreement”), contains a covenant requiring TCEH to deliver annual financial statements that are not qualified as to the status of TCEH and its subsidiaries as a going concern. As a result of the anticipated inclusion of the explanatory paragraph regarding substantial doubt about TCEH’s ability to continue as a going concern, TCEH will not be in compliance with this covenant. The TCEH Credit Agreement provides for a 30 day grace period for a breach of this covenant before an event of default may be deemed to have occurred. The current principal amount outstanding under the TCEH Credit Agreement is approximately $22.635 billion.

A breach of this covenant in the TCEH Credit Agreement would result in defaults under debt agreements at different entities within EFH Corp.’s capital structure as a result of cross acceleration or default provisions. Upon the occurrence of an event of default under any of these debt agreements, unless the borrower files for Chapter 11 bankruptcy protection, the lenders or noteholders thereunder could elect to declare all amounts outstanding under such debt agreements to be immediately due and payable and/or terminate all commitments to extend further credit. Such actions by those lenders or noteholders would cause cross defaults or accelerations under other obligations. If the borrower of such debt were unable to repay those amounts, the lenders or noteholders could proceed against any collateral granted to them to secure such debt. In the case of a default under debt that is guaranteed, holders of such debt could also seek to enforce the guarantees. If lenders or noteholders accelerate the repayment of all borrowings, EFH Corp. and its subsidiaries would not have sufficient assets and funds to repay those borrowings. Such occurrence (or the failure to reach agreement in the discussions described above) would result in EFH Corp. and its applicable subsidiaries (but not Oncor Electric Delivery Holdings Company LLC and its subsidiaries) filing for protection under Chapter 11 of the US Bankruptcy Code.

In consideration of the additional time required to evaluate the effects of these events on the financial statements and disclosures included in the Companies’ Annual Reports on Form 10-K, such Form 10-Ks cannot be timely filed without unreasonable effort and expense.

Concurrently with the filing of this Form 12b-25, EFH Corp., EFIH and EFCH have filed a Current Report on Form 8-K that includes information regarding the discussions with creditors of the Companies, the election not to make certain interest payments, and related matters.

PART IV — OTHER INFORMATION

If so, attach an explanation of the anticipated change, both narratively and quantitatively, and, if appropriate, state the reasons why a reasonable estimate of the results cannot be made.

CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This Notification of Late Filing on Form 12b-25 contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, which are subject to risks and uncertainties. All statements, other than statements of historical facts, are forward-looking statements. Readers are cautioned not to place undue reliance on forward-looking statements. Although the registrant believes that in making any such forward-looking statement its expectations are based on reasonable assumptions, any such forward-looking statement involves uncertainties and is qualified in its entirety by reference to the discussion of risk factors under Item 1A, “Risk Factors” and the discussion under Item 7, “Management’s Discussion and Analysis of Financial Condition and Results of Operations” in the Annual Report on Form 10-K filed by EFH Corp. in 2013. Any forward-looking statement speaks only at the date on which it is made, and except as may be required by law, the registrant undertakes no obligation to update any forward-looking statement to reflect events or circumstances after the date on which it is made or to reflect the occurrence of unanticipated events. New factors emerge from time to time, and it is not possible for the registrant to predict all of them; nor can the registrant assess the impact of each such factor or the extent to which any factor, or combination of factors, may cause results to differ materially from those contained in any forward-looking statement. As such, readers should not unduly rely on such forward-looking statements.

Energy Future Holdings Corp.

(Name of Registrant as Specified in Charter)

has caused this notification to be signed on its behalf by the undersigned hereunto duly authorized.