Mr. Justice Jackson
delivered the opinion of the Court.
The question in this case is whether the Acts of Congress and the administrative regulations thereunder afford a basis on which we may reconsider the decision in [372]*372Eisner v. Macomber, 252 U. S. 189, and pass on the Government’s request that it be overruled.
During the calendar year 1939 respondent owned 101 shares of common stock of the Standard Oil Company of New Jersey. Twice during the year that corporation made appropriate transfers from, earned surplus to its capital accounts, in amounts less than the net accumulation of earnings and profits subsequent to February 28, 1913, and against them issued stock dividends. On June 15, 1939, respondent received a dividend of 1.01 such shares having a fair market value of $42.93. On December 15, 1939, she received a further dividend of 1.53 shares, which had a fair market value of $66.08. These dividends were in common stock identical with the stock on which they were declared, which was the only stock outstanding at the time they were made. The dividend stock was not sold, redeemed, or in any way realized upon, and the taxpayer did not include it as income in her return for 1939. The Commissioner did so include it, and on December 8, 1941, sent her a notice of deficiency in the amount of $9.60. The Board of Tax Appeals reversed his determination,, and the Circuit Court of Appeals for the Second Circuit affirmed on the authority of Eisner v. Macomber, supra. 129 F. 2d 321. Because of the importance of the question we granted certiorari.
The tax is asserted under the general provision of § 22 (a) of the Internal Revenue Code that income includes “dividends,” together with the specific provision of § 115 (f) (1) that: “A distribution made by a corporation to its shareholders in its stock or in rights to acquire its stock shall not be treated as a dividend to the extent that it does not constitute income to the shareholder within the meaning of the Sixteenth Amendment to the Constitution.” 1
[373]*373Was Congress thereby saying that such a dividend as we have here is not being taxed, in view of the Eisner v. Macornber decision, or was it saying that regardless of that decision it is being taxed? Events which must be considered to determine which Congress intended begin with the enactment of the Revenue Act of 1913, which taxed corporate “dividends” in general but said nothing of stock dividends in particular.2 The Treasury attempted to tax them, and this Court held that a dividend of common stock paid on stock of the same kind was not income within the meaning of the Act, intimating, however, that as used in the Sixteenth Amendment “income” might have a wider scope. Towne v. Eisner, 245 U. S. 418 (1918). Congress had meanwhile provided that a “stock dividend shall be considered income, to the amount of its cash value.” 3 Under that Act the Commissioner asserted that a dividend in common stock paid on common stock constituted income when received. This Court held it was not income within the meaning of the Sixteenth Amendment, chiefly for the reason that income had not been severed from capital or realized by such a distribution. Eisner v. Macomber, 252 U. S. 189 (1920). This decision was by a divided Court, Justices Holmes and Brandéis each writing a dissenting opinion, in which respectively Justices Day and Clarke joined. It was promptly and sharply criticised.4
[374]*374Although Eisner v. Macomber dealt only with a dividend of common stock to common stockholders, it was at once accepted as the basis for a broader exemption. The Treasury ruled that receipt of dividend stock generally was not income, and Congress provided in § 201 (d) of the Revenue Act of 1921 that “A stock dividend shall not be subject to tax . . .”5 Treasury Regulations under this statute and subsequent reenactments construed it as covering all dividends paid in stock of the distributing corporation.6
There the matter stood for nearly fifteen years, although in the meantime this Court pointed out in reorganization cases that a distinction existed between the type of stock dividend before it in Eisner v. Macomber and one which gave the stockholder a different stock, or different proportionate interests, than before. United States v. Phellis, 257 U. S. 156 (1921); Rockefeller v. United States, 257 U. S. 176 (1921); Cullinan v. Walker, 262 U. S. 134 (1923) ; Weiss v. Stearn, 265 U. S. 242 (1924); Marr v. United States, 268 U. S. 536 (1925).
[375]*375Inaction did not mean, however, that persons who received stock dividends were escaping all support of the revenues. Taxation was only postponed, as is taxation of many securities taken in corporate reorganizations, until sale or other realization has occurred. Their proceeds when realized have always been taxable as income. The Treasury had come to compute the postponed tax under Regulations which as to some classes of stock apportioned the cost basis between the old stock and the dividend stock in accordance with their respective fair market values at the time the stock dividend was issued.7 On March 30, 1936, this Court granted certiorari in Koshland Helvering, 298 U. S. 441, in which the taxpayer challenged the validity of the apportionment Regulations. 297 U. S. 702. She had owned certain preferred stock and had received a dividend of common shares thereon. The preferred was thereafter redeemed, and the Commissioner applied the allocation rule, which reduced the cost basis of this old stock. This, of course, increased her gain on the redemption of the old stock and added to her tax. She argued that her dividend, notwithstanding Eisner v. Macomber, to which she gave a narrow reading, was constitutionally taxable as income at the time received. The Court held unanimously and squarely that the dividend in question did constitute income within the Sixteenth Amendment, and in effect limited Eisner v. Macomber to the kind of dividend there dealt with. But it did not overrule that decision or question its authority as to dividends such as we have in this case. With two Justices dissenting it struck down the apportionment regulations as being beyond statutory authorization.
[376]*376While the Court was considering stock dividends in the Koshland case, Congress was considering them in connection with the pending Revenue Act for 1936.
On March 3, 1936, the President had suggested the enactment of a tax upon the undistributed income of corporations.8 On March 26, 1936, and while the taxpayer’s petition for certiorari in the Koshland case was pending, a Subcommittee of the House Ways and Means Committee recommended that such a tax be enacted in lieu of the existing capital-stock, excess-profits, and income taxes on corporations.9 It was thought by some authorities that imposition directly upon shareholders of a tax based on their pro rata shares of corporate earnings would be more satisfactory than the undistributed-profits tax.10 Serious consideration of this method, which had been employed in [377]*377earlier times,11 was foreclosed by the belief that Eisner v. Macomber made it “impossible” to put into effect.12
[378]*378The statements of members of Congress and of responsible Treasury officials at the hearings and debates on the Act are at variance with the present assertion of the Government that Congress intended § 115 (f) (1) to challenge or override the decision to which it had in other sections of the Act accommodated itself.
At the hearings of the Congressional Committees the proposed tax was attacked as being a measure which would have the effect of forcing the distribution by corporations of assets needed in their business. Its supporters anticipated the decision of this Court in the Koshland case and countered with statements that dividends taxable as income to the shareholders — which would have the effect of avoiding the undistributed-profits tax on the corporation13 — could be declared and the undistributed-profits tax avoided without the necessity of distributing assets.14 No testimony was given, however, that divi[379]*379dends such as we have in this case were legally taxable or intended to be taxed.15
[380]*380As reported by the House Ways and Means Committee and passed in the House, § 115 (f) (1) of the bill provided: “A distribution made by a corporation to its shareholders in stock of the corporation or in rights to acquire stock of the corporation shall be treated as a taxable dividend to the extent that such distribution constitutes income to the shareholder within the meaning of the Sixteenth Amendment to the Constitution and represents a distribution of earnings or profits accumulated after February 28, 1913.”16 The Committee Report stated that: “It is provided in § 115 (f) that stock dividends shall be subject to tax to the extent that such dividends constitute income to the shareholder within the meaning of the sixteenth amendment to the Constitution.”17
The manager of the Bill, Congressman Vinson of Kentucky, stated on the floor of the House, with reference to § 115 (f) (1): “In no sense is this an attack upon the Eisner against Macomber decision. There are many dividends received in stock and stock rights that are distinguishable from the character of stock dividend in the Macomber case, supra, and are actual realized taxable income. As we see it, a stock dividend that is not taxable is one in which the relative interest of each shareholder of a corporation is unchanged in his stock ownership.”18 He submitted a legal memorandum furnished by Arthur Kent, [381]*381Acting Chief Counsel of the Bureau of Internal Revenue, setting forth cases dealing with the taxability of stock dividends, sixteen of which, including Eisner v. Macomber, had held stock dividends nontaxable, and twelve of which had held that the dividends were not true stock dividends and thus were taxable. This memorandum was in support of Kent’s statement in response to Congressman Vinson’s questioning at the hearings before the House Ways and Means Committee, to the effect that “the constitutional immunity of the true stock dividend recognized or declared in Eisner v. Macomber does not apply to all types and varieties of so-called stock dividends.”19 Congressman Vinson called particular and favorable attention to an article approving the decision in Eisner v. Macomber, published in the same month by Professor Magill, who had served as Special Assistant to the Secretary of the Treasury in tax matters and has also served as Undersecretary of the Treasury.20 Congressman Vinson reiterated his views on the following day in response to questions by Congressman Treadway, leader of the opposition to the bill.21
[382]*382The opinion of this Court in the Koshland case was announced on May 18, 1936, six days after the Senate Finance [383]*383Committee concluded its hearings. This Committee reported out § 115 (f) (1) in the form in which it is found in the Act: “A distribution made by a corporation to its shareholders in its stock or in rights to acquire its stock shall not be treated as a dividend to the extent that it does not constitute income to the shareholder within the meaning of the sixteenth amendment to the Constitution.” It stated in explanation of the change: “This subsection of the House bill, under which stock dividends are made taxable to the full extent permitted by the Constitution, is retained by your committee, except for changes made necessary by virtue of the reported amendment of section 115 (a) and in the interest of greater clarity.” 22
Senators Black and La Follette of the Senate Finance Committee submitted a minority report recommending an increase in the undistributed-profits tax rates, and also that § 115 (f) (1) specifically adopt the formula of the recently decided Koshland case, for no apparent reason other than a belief that in its present form it did not clearly have the effect of taxing even the type of stock dividends which the Court held in that case could be taxed.
To this end they recommended that § 115 (f) (1) “Specifically provide that there shall be no undistributed-prof[384]*384its tax on stock dividends which are taxable income for the individual recipient because the stock 'gives the stockholder an interest different from that which his former stockholdings represented.'”23 In debate on the floor of the Senate, Senator Black said that: ''As all Senators know, until about 2 weeks ago it was generally believed that it was impossible to tax stock dividends as income of the recipient of those stock dividends. About 2 weeks ago, however, the Supreme Court of the United States rendered an opinion which appeared in the Record, in which it decided if those stock dividends were declared in a different type of stock than the stock which was originally held by the owner, that those dividends did constitute actual income — taxable income, if you please — in the hands of the stockholder recipient.
“That being true, we have provided in such manner as to avoid any possible misunderstanding, that stock dividends declared in such manner that they are taxable in the hands of the recipient will be considered as distributed profits against which no undistributed-profits tax is imposed.”24
Senator Bone asked: “Would it not be possible for corporations to evade the effect of that kind of decision of the Supreme Court by distributing stock of a character that would escape taxation?” Senator Black answered [385]*385that they could, but that they would then be subject to the undistributed-profits tax.25
In response to a question by Senator Adams whether it would not be possible to tax stockholders in corporations upon undistributed corporate earnings, as partnerships were taxed upon undistributed partnership earnings, Senator Black stated that this was “impossible,”26 but that “in order to achieve the same result we have suggested a proposal which imposes no corporate tax on undistributed profits if the corporation declares a stock dividend of such nature as to be taxable under the recent Supreme Court opinion. In that case, the case of Koshland against Helvering, the Court distinguished clearly and unequivocally between a normal stock dividend of the same kind and nature as the stock on which the dividend was declared and a stock dividend of a distinctly different nature from the stock on which the dividend was declared. In order to carry out and obtain the full benefit of that, so that we can permit every corporation, if it desires, to retain 100 cents of every dollar in its treasury, if its stockholders wish, we have provided that there shall not be one dollar of corporate undistributed profit tax imposed upon that corporation if it distributes its dividends in a stock dividend which is taxable in the hands of the stockholders.” 27
Senator La Follette said on the floor of the Senate that “under all these measures — under the House bill, under the Senate committee bill, and under this amendment— any corporation desiring to retain 100 percent of its statutory net income free from increased tax may do so by paying out to its stockholders a dividend which is taxable under the sixteenth amendment.”28
[386]*386Senator Robinson stated his approval of the proffered amendment, but suggested that it be withdrawn and the matter taken up in conference. The amendment was accordingly withdrawn, but was not acted upon by the conference.29
The meaning of § 115 (f) (1) was critical in the administration both of the undistributed-profits tax upon corporations and of the income tax upon shareholders. This was not its only importance, however. Like the earlier Revenue Acts, the Revenue Act of 1936 contained provisions intended to cope with the problem of evasion of income taxes by shareholders through failure to distribute corporate income.30 These provisions had been drafted to avoid the limitations set upon Congressional power by [387]*387Eisner v. Macomber. It was generally believed that they had failed, and would fail, fully to accomplish their purpose, and that fully effective provisions would entail a challenge of the authority of Eisner v. Macomber.31
In this state of affairs, the Treasury issued Regulations which plainly construed § 115 (f) (1) not as repudiating Eisner v. Macomber by taxing stock dividends but as exempting them and adopting the existing decisions, including Eisner v. Macomber. Article 115-7 of Regulations 94, issued under the Revenue Act of 1936, set forth references to the Court’s decisions in many cases, and said: “A stock dividend does not constitute income if the new shares confer no different rights or interests than did the old — the new certificates plus the old representing [388]*388the same proportionate interest in the net assets of the corporation as did the old.” Three examples followed, the second relating to a dividend identical with the one before us. The example concluded: “The stock so distributed does not constitute a taxable stock dividend to the shareholders.” The Treasury also issued a statement of general policy as to stock dividends, to the effect that it would allow a dividends-paid credit against the undistributed-profits tax with respect to stock dividends which were clearly taxable to stockholders and refuse such credit with respect to stock dividends which were “clearly non taxable to the shareholder”; and where taxability was a debatable question, it would tentatively allow a dividends-paid credit if the corporation claiming the credit should file proper waivers or agreements to protect the interests of the Government pending final determination of the taxability to shareholders of the distribution, either by closing agreement executed by all shareholders or by a final adjudication in court.32
Administration of § 115 (f) (1) was undertaken and continued upon the basis of this construction, and no effort was made to obtain a different one. On the contrary, the Government in this Court took the position that the meaning of § 115 (f) (1) was correctly stated by Congressman Vinson on the floor of the House as quoted infra, p. 380.33
Other agencies of the Government accepted this same view of the meaning of the statute, authorizing the issuance by corporations subject to their supervision of securities other than common stock, at variance with their usual policy and in order to permit the corporations to [389]*389do what the Treasury assured them was necessary to avoid the payment of undistributed-profits taxes.34
The undistributed-profits tax evoked a voluminous literature, which showed almost universal agreement with the correctness of the Treasury's contemporaneous statement of the meaning of the statute.35
We think if Congress had passed or intended to pass an Act challenging a well known constitutional decision of this Court there would appear at least one clear statement of that purpose either from its proponents or its adversaries. Not one contemporaneous word in or out of Congress discloses the purpose which the Government says we should find that this legislation accomplished.
Against this background, it was proposed to incorporate an undistributed-profits tax in the pending Revenue Act for 1938. As proposed and enacted, § 115 (f) (1) was the same as in the 1936 Act.36 Like earlier Acts, the Revenue Act of 1938, as proposed and enacted, contained provisions [390]*390intended to conform with the authority of Eisner v. Macomber37 and it was attacked as embodying the principle [391]*391of forcing the distribution of needed corporate assets. The rate of the undistributed-profits tax was, however, [392]*392very materially lower than in the 1936 Act.38 This would have had the effect of diminishing the amount which would be collected from the corporation as undistributed-profits tax despite the declaration of a nontaxable stock dividend. Despite these factors, again there was not the slightest suggestion of the view that § 115 (f) (1) had made or had intended to make all stock dividends taxable; on the contrary, there was continued recognition of the [393]*393authority of Eisner v. Macomber.39 Section 115 (f) (1) was reenacted while the Treasury Regulation and rulings on its meaning stood unamended and in their original form.40
The Treasury adhered to its earlier views of the meaning of § 115 (f) (1) by repromulgating its former Regulation under the Revenue Act of 1938 and under the Internal Revenue Code,41 and it stood unamended at the time of the receipt of the stock dividends here in question. Congress in 1939 enacted basis provisions incorporating the language of § 115 (f)(1).42 It was not until November 15, 1940, and after the receipt of the dividends here involved, that the Treasury amended the Regulation, and then only by striking out all after the first sentence.43 This action followed the decision of this Court in Helvering v. Bruun, 309 U. S. 461, on March 25, 1940, which rejected the concept that taxable gain could arise only when the taxpayer was able to sever increment from his original capital. It preceded by ten days the decision in Helvering v. Horst, 311 U. S. 112, which held that there was no exemption from taxation where economic gain is enjoyed “by some event other than the taxpayer’s personal receipt of money or property.” Id. at 116. Each of these deci[394]*394sions undermined further the original theoretical bases of the decision in Eisner v. Macomber.
The Government says that the time has come when Eisner v. Macomber must be overruled, and that we should construe § 115 (f) (1) as intended to tax the dividends here in question and thus to require reconsideration of that decision. It should be observed that the question of the constitutional validity of Eisner v. Macomber is plainly one of the first magnitude, but this is not to say that it is presented in this case. Under our judicial tradition we do not decide whether a tax may constitutionally be laid until we find that Congress has laid it. Unless the tax asserted by the Commissioner has been authorized by Congress, it fails of validity before we even reach the constitutional question. To reach that question we must decide whether Congress intended by § 115 (f) (1) to do what Eisner v. Macomber squarely held that it could not. We cannot find that it did.
The Government cannot sustain its position on a literal reading of § 115 (f) (1). Unlike the Revenue Act of 1916,44 it does not state that all stock dividends are taxable. Instead, § 115 (f) (1) qualifies the generality of § 22 (a) by providing that a distribution made in shares of the corporation’s stock “shall not be treated as a dividend to the extent that it does not constitute income to the shareholder within the meaning of the Sixteenth Amendment. . . .” (Italics supplied.) If the statute is to be literally read, use of “does” instead of some word of futurity indicates that the time of enactment or at the latest the time of receipt of the dividend is the critical one for determining taxability. Under either view these dividends would not be taxable. The parties are agreed that for the purposes of this decision the meaning of the Constitution must be found in the decisions of this Court, [395]*395and when these dividends were received Eisner v. Macomber fixed the meaning contrary to the Government’s position.
The administrative and legislative history of the statute squarely conflict with the Government’s position in this case.
The Treasury Regulation issued under § 115 (f) (1) immediately after it was first enacted states in terms that the statute was not intended to lay a tax on the facts of this case and of Eisner v. Macomber, and the Treasury advised taxpayers by another ruling that some stock dividends were “clearly” nontaxable. In White v. Winchester Club, 315 U. S. 32, 41, we said that such “substantially contemporaneous expressions of opinion are highly relevant and material evidence of the probable general understanding of the times and of the opinions of men who probably were active in the drafting of the statute.” 45 The statute was reenacted in its original form after having been in force for two years, and after a long controversy centering around the meaning of the statute which assumed throughout the correctness of the administrative construction. This Court has denied retroactive effects to amendments to valid Treasury Regulations which have survived reenactment of the statute, even in the absence of any affirmative indication that the subject-matter of the statute and Regulation was called to the attention of Congress.46 The effect of reenactment in the absence of [396]*396such affirmative indications of agreement has been stated in various and not entirely consistent terms.47 This is a question we do not now need to examine, for there are in this case many indications that Congress was in complete [397]*397agreement with the Treasury on the question of the tax-ability of the stock dividends here involved. We would think it unquestionable that in this case the Treasury could not retroactively amend the Regulation to the prejudice of the respondent, except for the Government’s assertion that it should be disregarded upon the authority of Helvering v. Hallock, 309 U. S. 106, 121, note 8, and that, in any event, under § 3791 (b) of the Internal Revenue Code the Secretary or Commissioner must be held to have authority in any case to make a retroactive amendment of a Regulation.
The Hallock case is clearly inapposite. There it was held that Treasury Regulations issued more than 11 years after the enactment of the governing Revenue Act of 1926,48 in submission to the decision of this Court in 1935 of the St. Louis Trust Co. cases, 296 U. S. 39, 48, could not prevent the Court from overruling those cases on facts entirely antedating them. That Regulation did not purport to construe the meaning of the statute, as did this one, but simply to acknowledge a constitutional limit imposed by this Court upon the operation of a previously enacted statute; it was not in effect when the transactions involved were entered upon; and there had been no reenactment of the statute while the Regulation was in force.
Nor do we concur in the Government’s argument that the legislative history of § 3791 (b) of the Internal Revenue Code requires reconsideration of our decision as to the effect of a corresponding provision of the Revenue Act of 1928 in Helvering v. R. J. Reynolds Tobacco Co., 306 U. S. 110, 116.49 We think that in the circumstances of this [398]*398case the administrative construction in effect at the time of the receipt of the stock dividends here in issue must be given controlling effect.
[399]*399We would be reluctant, in any event, to find that Congress intended to hold the effect of § 115 (f) (1) in abeyance until the Treasury should decide that the time was ripe to challenge Eisner v. Macomber and carry its challenge to this Court. Such an intention would be a serious departure from the usual policy of Congress to provide the taxpayers and tax-gatherers with a practical basis for the timely settlement of questions of taxation arising each year. At the times of enactment, the problem of delay in obtaining decisions of this Court was a matter of grave concern to those concerned with the administration and furnishing of the revenues.50
The Government’s assertion that Congress intended to hold the meaning of § 115 (f) (1) in suspense until the termination of years of litigation is in conflict with our recent decision in Parker v. Motor Boat Sales Co., 314 U. S. 244. There we were called upon to construe § 3 (a) of the Longshoremen’s and Harbor Workers’ Act, 44 Stat. 1424, which made compensation payable only if “recovery for the disability or death through workmen’s compensation proceedings may not validly be provided by State law.” Its statement in such terms was due to this Court’s decision in Southern Pacific Co. v. Jensen, 244 U. S. 205, a much criticized and somewhat impaired, but not over[400]*400ruled, decision which held federal power exclusive and state compensation laws forbidden in an area of “shadowy limits.” The Court, speaking through Mr. Justice Black, said, “An interpretation which would enlarge or contract the effect of the proviso in accordance with whether this Court rejected or'reaffirmed the constitutional basis of the Jensen and its companion cases cannot be acceptable. The result of such an interpretation would be to subject the scope of protection that Congress wished to provide, to uncertainties that Congress wished to avoid.” Id. at 248, 250.
The Government urges that we read into the Congressional Act an intent to tax these dividends because of considerations that we do not think are entitled to any weight. It argues that the form of § 115 (f) (1) is attributable to “embarrassment” which would have been incident to a “frontal attack” on Eisner v. Macomber. There is ample ground to know that the prospect of conflict in opinion with this Court on constitutional questions was not sufficient so to mute the 74th and 75th Congresses.51 This was as it should be. There is no reason to doubt that this Court may fall into error as may other branches of the Government. Nothing in the history or attitude of this Court should give rise to legislative embarrassment if in the performance of its duty a [401]*401legislative body feels impelled to enact laws which may require the Court to reexamine its previous judgments or doctrine.52 The Court differs, however, from other branches of the Government in its ability to extricate itself from error. It can reconsider a matter only when it is again properly brought before it in a case or controversy; and if the case requires, as a tax case does,53 a statutory basis for a case, the new case must have sufficient statutory support.
And, if we were to assume Congressional “embarrassment” and take it into consideration, we would also be required to weigh the many other political factors which may have motivated the choice employed in the language of § 115 (f) (1). Those in favor of the bill may have believed that the adoption of existing decisions was the [402]*402most that was politically possible; those who opposed it may have thought it desirable as matter of tax policy to defer taxation of the stock dividend until realization.54 Needless to say, speculation upon such factors has no place in the construction of Acts of Congress.
We are asked to make a retroactive holding that for some seven years past a multitude of transactions have been taxable although there was no source of law from which the most cautious taxpayer could have learned of the liability. If he consulted the decisions of this Court, he learned that no such tax could be imposed; if he read the Delphic language of the Act in connection with existing decisions, it, too, assured him there was no intent to tax; if he followed the Congressional proceedings and debates, his understanding of nontaxability would be confirmed; if he asked the tax collector himself, he was bound by the Regulations of the Treasury to advise that no such liability existed. It would be a pity if taxpayers could not rely on this concurrent assurance from all three branches of the Government. But we are asked to brush all this aside and simply to decree that these transactions are taxable anyway.
[403]*403Nor is the effect on taxpayers the only consequence of accepting such a proposal. It would unsettle tax administration and subject the Treasury itself to many demands in ways that we cannot anticipate and provide for. Many have sold dividend stocks and paid the postponed tax at higher rates than if they had been taxed as is now proposed. Many have paid on the sale of the original stock because of allocation of part of the dividend to reduce the cost base thereof. Many corporations have been refused deductions on account of this type of stock dividend in computing their undistributed corporate earnings tax, which would become entitled to them. Overhanging the whole effort to accommodate these past transactions to a new retroactive law would be the statute of limitations barring sometimes the Government and sometimes the taxpayer with capricious effects. To rip out of the past seven years of tax administration a principle of law on which both Government and taxpayers have acted would produce readjustments and litigation so extensive we would contemplate them with anxiety. We have recently held as to another questioned decision of this Court that a long period of accommodations to an older decision sometimes requires us to adhere to an unsatisfactory rule to avoid unfortunate practical results from a change. Davis v. Department of Labor, 317 U. S. 249. We think this another example of the same principle.
The Government acknowledges the hardship which would be incident to the rule we are now asked to declare, and promises its assistance in obtaining legislative correction. It says that: “We are informed by the Treasury that it has no intention of harassing taxpayers with respect to liability for past years, and that if Eisner v. Ma-comber is overruled it intends immediately to recommend to Congress legislation which would relieve taxpayers of any unfair retroactive burden that might result from such overruling. . . .”
[404]*404Of course, if there were an adequate basis in statute and regulation for the tax in question, it is difficult to understand why its collection should be regarded as “harassing.” This assurance that if we will but find that Congress has intended to lay the tax it will be asked to declare that it does not intend it to be collected is hardly reassuring that the decision contended for would be what Congress intended. Since it is acknowledged that legislation would be required to adjust equities that are beyond judicial power and to prevent our decision’s being used to harass taxpayers, we may well inquire why the legislation should not precede the judicial decision. Why should we be asked to impose by interpretation a tax which the Treasury intends to ask Congress to lift?
We are unable to find that Congress intended to tax the dividends in question, and without Congressional authority we are powerless to do so. That being the case, we cannot reach the reconsideration of Eisner v. Macomber on the basis of the present legislation and Regulations.
The decision below is
Affirmed.
Mr. Justice Rutledge did not participate in the consideration or decision of this case.