PPL Corp. v. Comm'r of Internal Revenue, 569 U.S. 329

UK imposed a one-time windfall tax in 1997 on 32 privatized companies; the issue is whether the tax is creditable against U.S. taxes under 26 U.S.C. § 901(b)(1).
Tax formula: P Tax = 23% [(365 × (P/D) × 9) − FV] D, with D as initial-period days, P as profits, FV as privatization value, and a fixed P/E ratio of 9; 27 companies had 1,461 days, 5 varied.
PPL owned 25% of South Western Electricity plc; its windfall tax burden was £90,419,265; PPL claimed § 901 credit, the Commissioner denied, Tax Court favored creditability, Third Circuit reversed, and certiorari was granted.
Treasury Regulations provide creditability depends on predominant character—whether the tax is predominantly an income tax in the U.S. sense—using a net-income framework (realization, gross receipts, net income).
The Court held the windfall tax is predominantly an excess profits tax (income tax) because it taxes profits above a threshold, reformulating the base shows a net-income/profits focus, not merely a value difference.
The opinion discusses outliers (e.g., Railtrack Group) with shorter initial periods; the majority treats 27 companies as the defining group, while noting outliers affect creditability under 26 C.F.R. § 1.901-2(a)(1)(ii).

Issue	Plaintiff's Argument	Defendant's Argument	Held
Creditability under § 901(b)(1)	PPL contends the windfall tax is an excess profits tax (net income) and thus creditable.	Commissioner argues the tax is a value-based levy not consistently an income tax and questions its net income realization.	Windfall tax is creditable as an excess profits/income tax.
Impact of outliers on predominant character	Outliers with different initial periods should be included; the tax remains an income tax.	Outliers improperly distort the predominant character analysis; focus should be on majority.	Predominant character analysis centers on the 27 uniform initial-period companies; tax still creditable.
Substance vs. form in tax characterization	Tax is essentially a tax on profits above a threshold, i.e., net income.	Tax is a difference-based calculation between values, potentially not net income.	Substance shows the tax operates as a net income/excess profits tax; creditable.
Algebraic rearrangements for net income	Rearrangements demonstrate the base reflects profits vs. flotation value, aligning with net income.	Imputed or rearranged bases may misstate gross receipts and fail net income test.	Rearrangements valid; tax satisfies net income and gross receipts tests under § 1.901-2.

Biddle v. Commissioner, 302 U.S. 573 (1938) (banking/creditability framework for foreign taxes; 'predominant character' standard)
United States v. Goodyear Tire & Rubber Co., 493 U.S. 132 (1989) (foreign tax creditability; application of § 902/901 principles)
Heiner v. Mellon, 304 U.S. 271 (1938) (state-law definitions not controlling in federal tax context)
Commissioner v. Southwest Exploration Co., 350 U.S. 308 (1956) (tax law deals in economic realities; prevention of rigid form over substance)
Texasgulf, Inc. v. Commissioner, 172 F.3d 209 (2d Cir. 1999) (mining tax with processing allowance; net income analysis via estimation)
Entergy Corp. & Affiliated Subsidiaries v. Commissioner, 683 F.3d 233 (5th Cir. 2012) (outlier analysis and classification of foreign taxes under § 901)
Exxon Corp. v. Commissioner, 113 T.C. 338 (1999) (regulatory framework for creditability; substantive net income focus)