delivered the opinion of the Court.

In Carson v. Roane-Anderson Co., 342 U. S. 232, it was held that § 9 (b) of the Atomic Energy Act1 barred the collection of the Tennessee sales and use tax in connection with sales to private companies of personal property used by them in fulfilling their contracts with the Atomic Energy Commission. In 1953, Congress repealed the statutory immunity for activities and properties of the AEC contained in § 9 (b) in order to place Atomic Energy Commission contractors on the same footing as other contractors performing work for the Government.2 In 1955 Tennessee amended its statute by adding a contractor’s use tax which imposes a tax upon contractors using property in the performance of their contracts with others, irrespective of the ownership of the property and of the place where the goods are purchased. This tax, at the sales and use tax rate, is measured by the purchase price or fair market value of the property used by the contractor and is to be collected only when a sales tax on local purchases or a compensating use tax on out-of-state goods has not previously been collected in connection with the same property.3

*41Union Carbide Corp. and H. K Ferguson Co. have contracts with the Atomic Energy Commission relating to work and services to be performed at the Oak Ridge, Tennessee, complex. Carbide’s contract obligates it to manage, operate and maintain the Oak Ridge plants and facilities in accordance with such directions and instructions not inconsistent with the contract as the Commission deems necessary to issue from time to time. In the absence of applicable instructions, Carbide is to use its best judgment, skill and care in all matters pertaining to performance. Carbide is charged with the duty of procuring materials, supplies, equipment and facilities although the Government retains the right to furnish any of these items. Payment for purchases is to be made with government funds, and title to all property *42passes directly from the vendor to the United States.4 Carbide is generally free to make purchases up to $100,000 without prior approval.

Although Carbide exercises considerable managerial discretion from day to day in performing the contract, the Commission retains the right to control, direct and supervise the performance of the work and has issued directions and instructions governing large areas of the operation. Carbide has no investment in the Oak Ridge facility and at the time of this litigation employed some 12,000 employees and supervisors to perform the contract. Its annual fee, renegotiated periodically, was $2,751,000 at the time of suit.

The Ferguson contract was a contract to perform construction services relating both to new facilities and to the modification of the existing plant. The contract called for performing those projects ordered by the Commission. Ferguson also operated under instructions and directions of the AEC, it owned none of the property used in the performance of its contract and its purchases, of property were handled in a manner similar to that *43employed in the case of Carbide except that Ferguson was free to purchase without the consent of the Commission only up to $10,000. Ferguson’s compensation is negotiated twice a year on the basis of the value of the services Ferguson performed during the preceding six months, a fee of $20,000 having been paid for the six months preceding suit.

Tennessee collected from Carbide and Ferguson a sales and contractor’s use tax upon purchases made by them under their contracts with the Commission. The companies and the AEC sued to recover these taxes claiming that their collection infringed upon the implied constitutional immunity of the United States. The Tennessee Supreme Court refused to permit the collection of the sales tax 5 but sustained the collection of the contractor’s use tax. This tax, it was held, is imposed upon the use by a contractor of tangible personal property whether the title is in him or in another, and whether or not the other has immunity from state taxation. The contractor’s tax “was intended to be and is a tax upon the use per se by such a contractor. . . . [T]he tax is on [his] private use for [his] own profit and gain, and not a tax directly upon the Government.” 211 Tenn 139, 163, 164, 363 S. W. 2d 193, 203, 204. We noted probable jurisdiction to resolve another of the recurring conflicts between the power of the State to tax persons doing business within its borders and the immunity of the Federal Government, its instru-mentalities and property from state taxation. 375 U. S. 808. We affirm.

*44The Constitution immunizes the United States and its property from taxation by the States, M‘Culloch v. Maryland, 4 Wheat. 316, but it does not forbid a tax whose legal incidence is upon a contractor doing business with the United States, even though the economic burden of the tax, by contract or otherwise, is ultimately borne by the United States. James v. Dravo Contracting Co., 302 U. S. 134; Craves v. New York, 306 U. S. 466; Alabama v. King & Boozer, 314 U. S. 1. Nor is it forbidden for a State to tax the beneficial use by a federal contractor of property owned by the United States, even though the tax is measured by the value of the Government’s property, United States v. City of Detroit, 355 U. S. 466, and even though his contract is for goods or services for the United States. Curry v. United States, 314 U. S. 14; Esso Standard Oil Co. v. Evans, 345 U. S. 495; United States v. Township of Muskegon, 355 U. S. 484. The use by the contractor for his own private ends — in connection with commercial activities carried on for profit — is a separate and distinct taxable activity.

The United States accepts all this but insists that under the present contracts Carbide’s and Ferguson’s use of government property is not use by them for their own commercial advantage which the State may tax but a use exclusively for the benefit of the United States. Since they are paid for their services only, make no products for sale to the Government or others, have no investment in the Oak Ridge facility, do not stand to gain or lose by their efficient or nonefficient use of the property, and take no entrepreneurial risks, their use of government property, it is claimed, is in reality use by the United States.

We are not persuaded. In the first place, from the facts in this record it is incredible to conclude that the use of government-owned property was for the sole benefit of the Government. Both companies have a substantial stake in the Oak Ridge operation and a separate *45taxable interest. Both companies maintain a sizable number of employees at Oak Ridge, Carbide some 12,000 men and Ferguson at times over 1,000, and both companies were paid sizable fees over and above their cost, Carbide over $2,000,000 a year. No one suggests that either Carbide or Ferguson has put profit aside in contracting with the Commission, that the fee of either company is not set with commercial, profit-making considerations in mind or that the operations of either company at Oak Ridge were not an important part of their regular business operations. “The vital thing” is that Carbide, as well as Ferguson, “was using the property in connection with its own commercial activities.” United States v. Township of Muskegon, 355 U. S. 484, 486.6

*46Secondly, it does not help at all to say that the companies were engaged in furnishing services only, had no investment or risks and made no products for sale to the Government or to others. Undoubtedly a service industry has different characteristics than a manufacturing operation, but the differences are irrelevant for present purposes. The commercial world is replete with profit-making service industries contracting with the Government on a cost-plus basis, using government properties in the performance of the contract and pursuing their own commercial ends within the meaning of United States v. Township of Muskegon, supra. Whether manufacturing products for sale to the Government or furnishing services, the cost-plus contractor has undertaken contractual obligations. If he properly performs his contract, he earns his fee; if he does not, he may lose the contract, be liable for damages and be forced to liquidate the organization which was built to perform the contract. Whatever limitations there are on entrepreneurial risks derive from the fact the companies perform under cost-plus-fixed-fee contracts, a widespread method of contracting with the Government. The Government's argument, if accepted, would not only insulate the cost-plus management contractor from state taxation but also those who make products or perform construction work on a cost-plus basis, a result foreclosed by the Court's prior decisions which the Government seems to accept. Curry v. United States, supra; United States v. Township of Muskegon, supra.

In Muskegon, supra, the Court remarked that “[t]he case might well be different if the Government had reserved such control over the activities and financial gain of Continental that it could properly be called a 'servant' of the United States in agency terms.” The Government urges that this is such a case. According to the Government, this case should be viewed as though the *47Commission was doing its own work through its own employees, the legal incidence of the tax therefore falling on it. But, as in Muskegon, we cannot believe that either Carbide or Ferguson was “so assimilated by the Government as to become one of its constituent parts.” 355 U. S., at 486.

Because of the extraordinary range and complexity of the work to be performed in the research and development of atomic energy, Congress empowered the AEC to choose between performing these undertakings directly, through its own facilities, personnel and staff, and seeking the assistance of private enterprise by means of grants and contracts. Act of August 30, 1954, c. 1073, 68 Stat. 919, 927-928, 42 U. S. C. §§ 2051 (a), 2052. In order to utilize the skill, technical know-how, knowledge and experience of American industry, the Government has, since the inception of the atomic energy program, generally chosen private companies to conduct the various and sundry activities involved in the undertaking, including the management and operation of Atomic Energy plants. See Carson v. Roane-Anderson Co., supra. As is well stated in the preface to Carbide’s contract:

“ [S] uch agreement arose out of the need for the services of an organization with personnel of proved capabilities, both technical and administrative, to manage and operate certain facilities of the Commission and to perform certain work and services for the Commission; and the Commission recognizes the Corporation as an organization having such personnel, and that the initiative, ingenuity and other qualifications of such personnel should be exercised ... to the fullest extent practicable ....’’

The help of these companies was not sought merely to supply skilled manpower for employment by the United States and it is not argued that Carbide’s 12,000 men have somehow become employees of the Commission rather *48than of Carbide. See Powell v. United States Cartridge Co., 339 U. S. 497; Mahoney v. United States, 216 F. Supp. 523 (D. C. E. D. Tenn.). Of course there are governmental directives and instructions which must be obeyed, for the Commission decides the uses of and needs for fissionable material; and, of course, in the sensitive area of atomic energy operations the Commission’s controls are subject to modification and change in the light of technical and other developments.7 But Carbide and Ferguson brought to the Oak Ridge operation both skill and judgment the United States needed and did not have and there is substantial room for the exercise of both, within and without the broad directives issued by the Commission. Should the Commission intend to build or operate the plant with its own servants and employees, it is well aware that it may do so and familiar with the ways of doing it. It chose not to do so here. We cannot conclude that Carbide and Ferguson, both cost-plus contractors for profit, have been so incorporated into the government structure as to become instrumentalities of the United States and thus enjoy governmental immunity.

*49It is undoubtedly true, as the Government points out, that subjection of government property used by AEC contractors to state use taxes will result in a substantial future tax liability. But this result was brought to the attention of Congress in the debates on the repeal of § 9 (b),8 which exempted the activities of AEC contractors from state taxation; indeed the AEC argued that the repeal would substantially increase the cost of the atomic energy program by subjecting AEC contractors to state “sales and use taxes” and “business and occupation” taxes.9 Nonetheless, Congress, well aware of the prin*50ciple that “constitutional immunity does not extend to cost-plus-fixed-fee contractors of the Federal Government, but is limited to taxes imposed directly on the United States,” S. Rep. No. 694, 83d Cong., 1st Sess., 2, repealed the statutory exemption for the declared purpose of placing AEC contractors in the same position as all other government contractors. Act of August 13, 1953, c. 432, 67 Stat. 575.10 The principles laid down in King & *51Boozer, Curry, Esso, and Muskegon, we think, strike a proper judicial accommodation between the interests of the States’ power to tax and the concerns of the Nation, they are workable, and we adhere to them. If they unduly intrude upon the business of the Nation, it is for Congress, in the valid exercise of its proper powers, not this Court, to make the desirable adjustment.

Affirmed.

concurring.

But for the legislative history set out in the Court’s opinion, ante, pp. 49-50, notes 8-10,1 would have thought this case an appropriate one for a thorough reconsideration of the principles governing federal immunity from state taxation, a subject which has long troubled this Court. See my opinion in the “Michigan cases,” 355 U. S., at 505. In view of the legislative history, I concur in the judgment and opinion of the Court.