Summary of Significant Accounting Policies	3 Months Ended
Mar. 31, 2026
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Note 1 – Summary of Significant Accounting Policies Basis of Presentation The unaudited condensed consolidated financial statements of T-Mobile US, Inc. (“T-Mobile,” “we,” “our,” “us” or the “Company”) include all adjustments of a normal recurring nature necessary for the fair presentation of the results for the interim periods presented. The results for the interim periods are not necessarily indicative of those for the full year. The condensed consolidated financial statements should be read in conjunction with our consolidated financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2025. The condensed consolidated financial statements include the balances and results of operations of T-Mobile and our consolidated subsidiaries. We consolidate majority-owned subsidiaries over which we exercise control, variable interest entities (“VIEs”) for which we are deemed to be the primary beneficiary and VIEs which cannot be deconsolidated, such as those related to our tower obligations as discussed in Note 8 - Tower Obligations. Intercompany transactions and balances have been eliminated in consolidation. Investments in entities that we do not control but have significant influence are accounted for under the equity method. We record our proportionate share of our equity method investees’ earnings (losses) within Other expense, net on our Condensed Consolidated Statements of Comprehensive Income. The preparation of financial statements in conformity with United States (“U.S.”) generally accepted accounting principles (“GAAP”) requires our management to make estimates and assumptions that affect the financial statements and accompanying notes. Estimates are based on historical experience, where applicable, and other assumptions that management believes are reasonable under the circumstances. Estimates are inherently subject to judgment and actual results could differ from those estimates. Accounting Pronouncements Adopted During the Current Year Interim Reporting In December 2025, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2025-11, “Interim Reporting (Topic 270): Narrow-Scope Improvements.” The standard improves the navigability of interim disclosures, clarifies when Topic 270 applies and provides additional interim disclosure guidance, including a principle to disclose material events since the most recent annual reporting period. The amendments do not change the underlying objectives of interim reporting but are designed to enhance clarity in application. We evaluated this standard and concluded our interim reporting disclosures are consistent with this standard. Accordingly, the adoption of this standard in the first quarter of 2026 did not have a material impact on our interim reporting disclosures. Internal-Use Software Accounting and Disclosures In September 2025, the FASB issued ASU 2025-06, “Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Targeted Improvements to the Accounting for Internal-Use Software.” The amendments remove all references to project stages in ASC 350-40, clarify the threshold entities apply to begin capitalizing costs and address challenges arising from the evolution of software development practices. The new guidance modernizes accounting for software developed using incremental and iterative methods, where the existing model provided limited direction on when capitalization should begin. The ASU also specifies that the disclosures under ASC 360-10, “Property, Plant, and Equipment—Overall,” apply to capitalized software costs accounted for under ASC 350-40, regardless of how those costs are presented in the financial statements. As of January 1, 2026, we have adopted this standard, and it was applied prospectively after this date. The adoption of this standard did not have a material impact on our condensed consolidated financial statements and related disclosures. Accounting Pronouncements Not Yet Adopted Disaggregation of Income Statement Expenses In November 2024, the FASB issued ASU 2024-03, “Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses.” The standard requires that public business entities disclose additional information about specific expense categories in the notes to financial statements for interim and annual reporting periods. The standard will become effective for us for our fiscal year 2027 annual financial statements and interim financial statements thereafter and may be applied prospectively to periods after the adoption date or retrospectively for all prior periods presented in the financial statements, with early adoption permitted. We plan to adopt the standard when it becomes effective for us beginning in our fiscal year 2027 annual financial statements, and we are currently evaluating the impact this guidance will have on the disclosures included in the Notes to the Consolidated Financial Statements.

The unaudited condensed consolidated financial statements of T-Mobile US, Inc. (“T-Mobile,” “we,” “our,” “us” or the “Company”) include all adjustments of a normal recurring nature necessary for the fair presentation of the results for the interim periods presented. The results for the interim periods are not necessarily indicative of those for the full year. The condensed consolidated financial statements should be read in conjunction with our consolidated financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2025.

The condensed consolidated financial statements include the balances and results of operations of T-Mobile and our consolidated subsidiaries. We consolidate majority-owned subsidiaries over which we exercise control, variable interest entities (“VIEs”) for which we are deemed to be the primary beneficiary and VIEs which cannot be deconsolidated, such as those related to our tower obligations as discussed in Note 8 - Tower Obligations. Intercompany transactions and balances have been eliminated in consolidation. Investments in entities that we do not control but have significant influence are accounted for under the equity method. We record our proportionate share of our equity method investees’ earnings (losses) within Other expense, net on our Condensed Consolidated Statements of Comprehensive Income.

The preparation of financial statements in conformity with United States (“U.S.”) generally accepted accounting principles (“GAAP”) requires our management to make estimates and assumptions that affect the financial statements and accompanying notes. Estimates are based on historical experience, where applicable, and other assumptions that management believes are reasonable under the circumstances. Estimates are inherently subject to judgment and actual results could differ from those estimates.

In December 2025, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2025-11, “Interim Reporting (Topic 270): Narrow-Scope Improvements.” The standard improves the navigability of interim disclosures, clarifies when Topic 270 applies and provides additional interim disclosure guidance, including a principle to disclose material events since the most recent annual reporting period. The amendments do not change the underlying objectives of interim reporting but are designed to enhance clarity in application. We evaluated this standard and concluded our interim reporting disclosures are consistent with this standard. Accordingly, the adoption of this standard in the first quarter of 2026 did not have a material impact on our interim reporting disclosures.

In September 2025, the FASB issued ASU 2025-06, “Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Targeted Improvements to the Accounting for Internal-Use Software.” The amendments remove all references to project stages in ASC 350-40, clarify the threshold entities apply to begin capitalizing costs and address challenges arising from the evolution of software development practices. The new guidance modernizes accounting for software developed using incremental and iterative methods, where the existing model provided limited direction on when capitalization should begin. The ASU also specifies that the disclosures under ASC 360-10, “Property, Plant, and Equipment—Overall,” apply to capitalized software costs accounted for under ASC 350-40, regardless of how those costs are presented in the financial statements. As of January 1, 2026, we have adopted this standard, and it was applied prospectively after this date. The adoption of this standard did not have a material impact on our condensed consolidated financial statements and related disclosures.

In November 2024, the FASB issued ASU 2024-03, “Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses.” The standard requires that public business entities disclose additional information about specific expense categories in the notes to financial statements for interim and annual reporting periods. The standard will become effective for us for our fiscal year 2027 annual financial

statements and interim financial statements thereafter and may be applied prospectively to periods after the adoption date or retrospectively for all prior periods presented in the financial statements, with early adoption permitted. We plan to adopt the standard when it becomes effective for us beginning in our fiscal year 2027 annual financial statements, and we are currently evaluating the impact this guidance will have on the disclosures included in the Notes to the Consolidated Financial Statements.