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): August 16, 2021

T-MOBILE US, INC.

(Exact Name of Registrant as Specified in Charter)

Registrant’s telephone number, including area code: (425) 378-4000

(Former Name or Former Address, if Changed Since Last Report):

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:

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

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.  ☐

On August 16, 2021, T-Mobile US, Inc. (“T-Mobile,” “we,” “our” or “us”) posted the following statement to its website:

We have been working around the clock to investigate claims being made that T-Mobile data may have been illegally accessed. We take the protection of our customers very seriously and we are conducting an extensive analysis alongside digital forensic experts to understand the validity of these claims, and we are coordinating with law enforcement.

We have determined that unauthorized access to some T-Mobile data occurred, however we have not yet determined that there is any personal customer data involved. We are confident that the entry point used to gain access has been closed, and we are continuing our deep technical review of the situation across our systems to identify the nature of any data that was illegally accessed. This investigation will take some time but we are working with the highest degree of urgency. Until we have completed this assessment we cannot confirm the reported number of records affected or the validity of statements made by others.

We understand that customers will have questions and concerns, and resolving those is critically important to us. Once we have a more complete and verified understanding of what occurred, we will proactively communicate with our customers and other stakeholders.

Forward-Looking Statements

This Current Report on Form 6-K includes forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. All statements other than statements of historical fact are forward-looking statements. These forward-looking statements are generally identified by the words “anticipate,” “believe,” “estimate,” “expect,” “intend,” “may,” “could” or similar expressions. Forward-looking statements are based on current expectations and assumptions, which are subject to risks and uncertainties and may cause actual results to differ materially from the forward-looking statements. Important factors that could affect future results and cause those results to differ materially from those expressed in the forward-looking statements include, among others, the following: data loss or other security breaches, including risks related to the cybersecurity incident discussed above, our ability to asses and remedy the cybersecurity incident, and legal, reputational and financial risks resulting from this or other cybersecurity incidents; natural disasters, public health crises, including the COVID-19 pandemic (the “Pandemic”), terrorist attacks or similar incidents; adverse economic, political or market conditions in the U.S. and international markets, including those caused by the Pandemic; competition, industry consolidation and changes in the market condition for wireless services; the scarcity and cost of additional wireless spectrum, and regulations relating to spectrum use; our inability to retain or motivate key personnel, hire qualified personnel or maintain our corporate culture; our inability to take advantage of technological developments on a timely basis; system failures and business disruptions, allowing for unauthorized use of or interference with our network and other systems; the impacts of the actions we have taken and conditions we have agreed to in connection with the regulatory proceedings and approvals of the Transactions (as defined below), including the acquisition by DISH Network Corporation (“DISH”) of the prepaid wireless business operated under the Boost Mobile and Sprint prepaid brands (excluding the Assurance brand Lifeline customers and the prepaid wireless customers of Shenandoah Personal Communications Company LLC (“Shentel”) and Swiftel Communications, Inc.), including customer accounts, inventory, contracts, intellectual property and certain other specified assets (the “Prepaid Business”), and the assumption of certain related liabilities (the “Prepaid Transaction”), the complaint and proposed final judgment (the “Consent Decree”) agreed to by us, Deutsche Telekom AG (“DT”), Sprint Corporation (“Sprint”), SoftBank Group Corp. (“SoftBank”) and DISH with the U.S. District Court for the District of Columbia, which was approved by the Court on April 1, 2020, the proposed commitments filed with the Secretary of the Federal Communications Commission (“FCC”), which we announced on May 20, 2019, certain national security commitments and undertakings, and any other commitments or undertakings entered into including but not limited to those we have made to certain states and nongovernmental organizations (collectively, the “Government Commitments”), and the challenges in satisfying the Government Commitments in the required time frames and the significant cumulative cost incurred in tracking, monitoring and complying with them; our inability to manage the ongoing commercial and transition services arrangements that we entered into with DISH in connection with the Prepaid Transaction, which we completed on July 1, 2020 (collectively, the “Divestiture Transaction”), and known or unknown liabilities arising in connection therewith; the effects of any future acquisition, investment, or merger involving us; any disruption or

failure of our third parties (including key suppliers) to provide products or services for the operation of our business; the occurrence of high fraud rates or volumes related to device financing, customer payment cards, third-party dealers, employees, subscriptions, identities or account takeover fraud; our substantial level of indebtedness and our inability to service our debt obligations in accordance with their terms or to comply with the restrictive covenants contained therein; adverse changes in the ratings of our debt securities or adverse conditions in the credit markets; the risk of future material weaknesses we may identify while we work to integrate and align policies, principles and practices of the two companies following the Merger (as defined below), or any other failure by us to maintain effective internal controls, and the resulting significant costs and reputational damage; any changes in regulations or in the regulatory framework under which we operate; laws and regulations relating to the handling of privacy and data protection; unfavorable outcomes of existing or future legal proceedings; our offering of regulated financial services products and exposure to a wide variety of state and federal regulations; new or amended tax laws or regulations or administrative interpretations and judicial decisions affecting the scope or application of tax laws or regulations; the possibility that we may be unable to renew our spectrum leases on attractive terms or the possible revocation of our existing licenses in the event that we violate applicable laws; interests of our significant stockholders that may differ from the interests of other stockholders; future sales of our common stock by DT and SoftBank and our inability to attract additional equity financing outside the United States due to foreign ownership limitations by the FCC; the volatility of our stock price and our lack of plan to pay cash dividends in the foreseeable future; failure to realize the expected benefits and synergies of the merger (the “Merger”) with Sprint, pursuant to the Business Combination Agreement with Sprint and the other parties named therein (as amended, the “Business Combination Agreement”) and the other transactions contemplated by the Business Combination Agreement (collectively, the “Transactions”) in the expected timeframes or in the amounts anticipated; any delay and costs of, or difficulties in, integrating our business and Sprint’s business and operations, and unexpected additional operating costs, customer loss and business disruptions, including challenges in maintaining relationships with employees, customers, suppliers or vendors; unanticipated difficulties, disruption, or significant delays in our long-term strategy to migrate Sprint’s legacy customers onto T-Mobile’s existing billing platforms; and changes to existing or the issuance of new accounting standards by the Financial Accounting Standards Board or other regulatory agencies. Given these risks and uncertainties, readers are cautioned not to place undue reliance on such forward-looking statements. We undertake no obligation to revise or publicly release the results of any revision to these forward-looking statements, except as required by law.

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.