with whom Justice White joins, concurring in part and dissenting in part in No. 89-1926, post, p. 573, and dissenting in No. 89-1965.
I agree that the early withdrawal penalties collected by Centennial Savings Bank FSB do not constitute “income by reason of the discharge ... of indebtedness of the taxpayer,” within the meaning of 26 U. S. C. § 108(a)(1) (1982 ed.), and that the penalty amounts are not excludable from Centennial's gross income. I therefore join Part III of the Court’s opinion in No. 89-1926.
*569I dissent, however, from the Court’s conclusions in these two cases that Centennial and Cottage Savings Association realized deductible losses for income tax purposes when each exchanged partial interests in one group of residential mortgage loans for partial interests in another like group of residential mortgage loans. I regard these losses as not recognizable for income tax purposes because the mortgage packages so exchanged were substantially identical and were not materially different.
The exchanges, as the Court acknowledges, were occasioned by Memorandum R-49, Record, Exh. 72-BT, issued by the Federal Home Loan Bank Board (FHLBB) on June 27, 1980, and by that Memorandum’s relaxation of theretofore-existing accounting regulations and requirements, a relaxation effected to avoid placement of “many S & L’s at risk of closure by the FHLBB” without substantially affecting the “economic position of the transacting S & L’s.” Ante, at 557. But the Memorandum, the Court notes, also had as a purpose the “facilit[ation of] transactions that would generate tax losses.” Ibid. I find it somewhat surprising that an agency not responsible for tax matters would presume to dictate what is or is not a deductible loss for federal income tax purposes. I had thought that that was something within the exclusive province of the Internal Revenue Service, subject to administrative and judicial review. Certainly, the FHLBB’s opinion in this respect is entitled to no deference whatsoever. See United States v. Stewart, 311 U. S. 60, 70 (1940); Graff v. Commissioner, 673 F. 2d 784, 786 (CA5 1982) (concurring opinion). The Commissioner, of course, took the opposing position. See Rev. Rul. 85-125, 1985-2 Cum. Bull. 180; Rev. Rul. 81-204, 1981-2 Cum. Bull. 157.
It long has been established that gain or loss in the value of property is taken into account for income tax purposes only if and when the gain or loss is “realized,” that is, when it is tied to a realization event, such as the sale, exchange, or other disposition of the property. Mere variation in value— *570the routine ups and downs of the marketplace — do not in themselves have income tax consequences. This is fundamental in income tax law.
In applying the realization requirement to an exchange, the properties involved must be materially different in kind or in extent. Treas. Reg. § 1.1001 — 1(a), 26 CFR §1.1001-1(a) (1990). This has been the rule recognized administratively at least since 1935, see Treas. Regs. 86, Art. 111-1, issued under the Revenue Act of 1934, and by judicial decision. See, e. g., Mutual Loan & Savings Co. v. Commissioner, 184 F. 2d 161 (CA5 1950). See also Mart v. United States, 268 U. S. 536, 541 (1925); Weiss v. Stearn, 265 U. S. 242, 254 (1924); United States v. Phellis, 257 U. S. 156 (1921). This makes economic as well as tax sense, for the parties obviously regard the exchanged properties as having equivalent values. In tax law, we should remember, substance rather than form determines tax consequences. Commissioner v. Court Holding Co., 324 U. S. 331, 334 (1945); Gregory v. Helvering, 293 U. S. 465, 469-470 (1935); Shoenberg v. Commissioner, 77 F. 2d 446, 449 (CA8), cert. denied, 296 U. S. 586 (1935). Thus, the resolution of the exchange issue in these cases turns on the “materially different” concept. The Court recognizes as much. Ante, at 559-560.
That the mortgage participation partial interests exchanged in these cases were “different” is not in dispute. The materiality prong is the focus. A material difference is one that has the capacity to influence a decision. See, e. g., Kungys v. United States, 485 U. S. 759, 770-771 (1988); Basic Inc. v. Levinson, 485 U. S. 224, 240 (1988); TSC Industries, Inc. v. Northway, Inc., 426 U. S. 438, 449 (1976).
The application of this standard leads, it seems to me, to only one answer — that the mortgage participation partial interests released were not materially different from the mortgage participation partial interests received. Memorandum R-49, as the Court notes, ante, at 557, n. 2, lists 10 factors that, when satisfied, as they were here, serve to classify the *571interests as “substantially identical.” These factors assure practical identity; surely, they then also assure that any difference cannot be of consequence. Indeed, nonmateriality is the full purpose of the Memorandum’s criteria. The “proof of the pudding” is in the fact of its complete accounting acceptability to the FHLBB. Indeed, as has been noted, it is difficult to reconcile substantial identity for financial accounting purposes with a material difference for tax accounting purposes. See First Federal Savings & Loan Assn. of Temple v. United States, 694 F. Supp. 230, 245 (WD Tex. 1988), aff’d, 887 F. 2d 593 (CA5 1989), cert. pending No. 89-1927. Common sense so dictates.
This should suffice and be the end of the analysis. Other facts, however, solidify the conclusion: The retention by the transferor of 10% interests, enabling it to keep on servicing its loans; the transferor’s continuing to collect the payments due from the borrowers so that, so far as the latter were concerned, it was business as usual, exactly as it had been; the obvious lack of concern or dependence of the transferor with the “differences” upon which the Court relies (as transferees, the taxpayers made no credit checks and no appraisals of collateral, see 890 F. 2d 848, 849 (CA6 1989)); 90 T. C. 372, 382 (1988); 682 F. Supp. 1389, 1392 (ND Tex. 1988); the selection of the loans by a computer programmed to match mortgages in accordance with the Memorandum R-49 criteria; the absence of even the names of the borrowers in the closing schedules attached to the agreements; Centennial’s receipt of loan files only six years after its exchange, id., at 1392, n. 5; the restriction of the interests exchanged to the same State; the identity of the respective face and fair market values; and the application by the parties of common discount factors to each side of the transaction — all reveal that any differences that might exist made no difference whatsoever and were not material. This demonstrates the real nature of the transactions, including nonmateriality of the claimed differences.
*572We should be dealing here with realities and not with superficial distinctions. As has been said many times, and as noted above, in income tax law we are to be concerned with substance and not with mere form. When we stray from that principle, the new precedent is likely to be a precarious beacon for the future.
I respectfully dissent on this issue.