ROBERTS, Justice.

This is a direct appeal to review a decision of the Circuit Court of Collier County invalidating a contract and two ordinances of the City of Naples, purporting to extend certain tax benefits to the appellants. In reaching his decision the chancellor, in his decree, construed Sections 1 and 5 of Article IX of the Constitution of Florida, F.S.A., and the appellate jurisdiction is therefore vested in this court. See McNayr v. State ex rel. Dupont Plaza Center, Inc., 166 So.2d 142 (Fla. 1964); Green v. Walter, 161 So.2d 830 (Fla. 1964); State ex rel. Glynn v. McNayr, 133 So.2d 312 (Fla. 1961).

Among other things, the chancellor found (1) ordinances 400 and 615 of the City of Naples to be invalid; (2) the contracts between the municipal corporation and the appellants (developers) to be invalid and unenforceable; and (3) that the taxing authorities of the City should reassess the property owned by the appellants (developers) involved in this litigation for the years 1962 and 1963; and in effect that the contracts were ultra vires and also barred by Sections 1 and 5, Article IX of the Constitution of Florida.

In 1954 the City of Naples adopted Ordinance No. 400 which provides:

"Section 1. All developers of land lying within the City of Naples, Florida, who desire to create subdivisions from lands composed generally of mangrove swamp, overflowed and other low lands, and who desire to take advantage of this Ordinance shall first submit to the Council for its approval, the method and the approximate cost of such improvements.

"Section 2. The Council shall then determine from such plans whether such development as proposed will benefit the City from the standpoint of health or safety or general welfare and should it so decide that such development is in the public interest, shall do the following provided that other ordinances and laws relating to plats and subdivisions are complied with: (a) Make a specific finding that the proposed development is in the public interest from the standpoint of health, safety or general welfare. (b) Agree to assess all lots in the subdivision, unimproved by physical buildings, to which title remains in the developer, whether it be a person, firm or corporation, as acreage until such time as sixty per cent of the lots have been sold, or the period of ten years has elapsed whichever shall occur first. (c) Enter into a binding contract with the developer guaranteeing the above for the term stated.

"Section 3. This ordinance is hereby declared to be in the public interest and designed to promote the health, safety and general welfare of Naples, Florida."

In 1957 certain amendments were made but the amendments are immaterial to the issues here involved.

For many years the City and various developers acted without objection under contracts similar or comparable to the following:

"It is hereby mutually agreed between the parties hereto that for the next 10 years, or until 60% of the lots shall be sold by Port Royal, Incorporated, whichever is sooner, all lots in the proposed subdivision shall be assessed for City tax purposes as acreage only and at valuations comparable to valuations assessed against other unimproved, submerged lands within the City limits; provided that in the event Port Royal, Incorporated, shall place buildings upon any of said lots while still assessed to it then and in that event the particular lot shall be treated and assessed as though sold."

The principal question in the taxpayers' class suit is whether a municipality has authority to make such contracts. The lower court, in a well-reasoned opinion, held that it did not and cited as authority Tampa Shipbuilding and Engineering Co. v. City of Tampa, 102 Fla. 549, 136 So. 458 (1931), and City of Tampa v. Kaunitz, 39 Fla. 683, 23 So. 416, 63 Am.St.Rep. 202 (1898). The Tampa Shipbuilding case held, inter alia, that without valid legislative authority, no city or town has power to bind itself, by contract, either to forebear to impose taxes on particular property, or to impose them only under given limitations, or on certain given conditions. The purpose of the contract there was to subsidize a shipbuilding plant in the City of Tampa with its various assets to a city community and the purpose of the contract in instant case is to encourage residential improvements, thus, hopefully, increasing the size of the tax roll. We have a similar situation in the City of Tampa case, supra, where the court stated 23 So. on page 420:

"(b) Did the city of Tampa have power, by contract or otherwise, to exempt from taxation the properties of the South Florida Division of the Savannah, Florida Western Railway Company and the Tampa Waterworks Company, and to perpetually bind itself to accept from the Tampa Bay Hotel Company $200 per annum in full for all city taxes, without regard to the value of its property, or the rate of taxation levied thereon? The plaintiff in error cites us to no authorities on this point. He plants himself upon the proposition that the exemptions were granted for a consideration, and that, consequently, they amounted to a contract with the city. But where does the city derive its authority to make such a contract? We have not been cited to any statute of this state authorizing the city to exempt this species of property from taxation, nor to make a contract so to do. Without valid legislative authority, no city or town has power to bind itself, by contract, either to forebear to impose taxes on particular property, or to impose them only under given limitations, or on certain given conditions."

In connection with the constitutional inhibitions, we have carefully considered the contention that the tax exemptions are for a valid municipal purpose, however, we find that the supposed consideration for the contracts is speculative and incidental and that the courts have held similar plans to be primarily for the benefit of a private enterprise and not primarily for the benefit of the public. City of Daytona Beach v. King, 132 Fla. 273, 181 So. 1 (1938); City of Bradentown v. State, 88 Fla. 381, 102 So. 556, 36 A.L.R. 1297 (1924). The subdivisions are owned and controlled by private persons, firms or corporations and the revenue accrues to these developers. In contrast, in Gwin v. City of Tallahassee, 132 So.2d 273 (Fla. 1961), revenue from an electrical generating plant accrued to the city which owned and operated the facilities, and the court there held that the function came within the concept of "municipal purpose" and was therefore entitled to the tax exemption. There is no question as to the good faith of the taxing authority, but the danger of allowing such power of exemption to exist is so manifest that our Constitution, Article IX, § 1 and § 5 prohibits the exercise of such power.

The chancellor buttressed his decision that the contract was void as being ultra vires by also holding, in effect, that §§ 1 and 5 of Article IX, Constitution of Florida, prohibit such tax advantages flowing to individuals. The chancellor was eminently correct in holding that such discrimination in favor of the appellants would violate § 1, Article IX of the Constitution.

By cross-appeal, the complaining taxpayers, relying on a portion of F.S. § 192.21 and a portion of § 193.23, F.S.A. contend that the City should be required to "back-assess" for 1959, 1960 and 1961, the subject lands at their fair and just valuation.

The chancellor denied the prayer that the City reassess the developers' lands under contract with the City for the three years prior to 1962, the year the action was commenced, stating in his final decree that "the taxing authorities of the municipal corporation are hereby directed to reassess the property owned by the developers and involved in this litigation for the years 1962 and 1963 and assess said properties for tax purposes as would have been done had the contracts with the defendant developers never existed." The cross-appellants argue in their brief that "[W]hen a city fails to follow the equal and just principle, and its charter fails to provide a corrective procedure, the Court should implement state law which will enforce the fundamental principle."

The cross-appellees contend that the claim of cross-appellants for the three years prior taxes allowed to be back-assessed under § 193.23 is barred by F.S. § 192.21, F.S.A. which provides in part: "* * * no assessment shall be held invalid unless suit be instituted within sixty days from the time the assessment shall become final * * *." They further contend that F.S. § 193.23 is inapplicable because the taxes had been levied and collected for those years and that the property did not escape taxation.

The question thus posed is whether the city may reassess at fair value property that had been undervalued for the prior three years. We conclude upon reason and authority that the city should be limited to reassessments subsequent to the commencement of this action.

The fact that the contracts with the City were declared void does not necessarily make the assessments themselves void or unlawfully assessed or levied. See City of Tampa v. Kaunitz, supra, 23 So. page 421:

"We think tax officers, like all others, are required to exercise good faith in performing their official duties. They should not use their official position or official discretion as a cover for fraudulent conduct in unequally and inequitably adjusting the burdens of taxation. For it is a salutary principle of law, which runs through all its branches, that fraud vitiates and annuls everything which it touches. If, therefore, tax officers intentionally commit an illegal act, with a fraudulent purpose in view, as where taxable property is intentionally omitted for an improper purpose, we have no doubt that the entire assessment is illegal and void. If, however, the omission to assess taxable property arises in consequence of a bona fide belief on the part of the taxing officers that the omitted property is exempt from taxation, or results from inadvertence or negligence, without any intent on their part to impose additional or unequal burdens upon other taxpayers, the assessment will not be held to be void."

Also in Dade County v. Dupont Plaza, Inc., 117 So.2d 849 (Fla.App. 3rd Dist. 1960) in a suit to avoid an assessment on grounds that it was excessive, it was held that no assessment of property taxes should be held invalid unless suit be instituted within sixty days from the time the assessment became final. In Rudisill v. City of Tampa, 151 Fla. 284, 9 So.2d 380 (1942), this court upheld the validity of the restrictive period allowed by statute [§ 192.21] stating, inter alia, "* * * The legislature is necessarily vested with power to enact necessary laws to secure a prompt collection of the annual tax. In the exercise of such powers they must not invade the constitutional rights of the property owner. Provision is made here, however, for the owner to make return of his property and value same for taxation. He has further remedy to petition the equalization board for appropriate relief. He is allowed a minimum of thirty days [prior to 1943 this section allowed 30 days] from the final act of the administrative officers to resort to the courts if he feels aggrieved by the administrative taxing authorities. While the time may appear relatively short, nevertheless it cannot be said that the time fixed by the legislature is so unreasonable as to amount to depriving him of his property without due process." Compare Nash v. Merritt Island Lumber Company, 110 So.2d 677 (Fla. App., 2nd Dist. 1959).

The tax assessor of the City of Naples merely used as a guideline a standard measure of values which has now been declared to be unfair.

Cross-appellants failed to institute suit within 60 days and the statute provides therefore that no assessment shall thereafter be held invalid.

The duty for each citizen to bear a just share of taxation, justice to other taxpayers, and the requirements of orderly government make it inequitable to give relief in all instances because there may be some inequality in an assessment which, if it in fact existed, could have been remedied by pursuing remedies in time for proper assessments to be made so that all may appropriately share tax burdens to support efficient government for the protection of the property rights of all. See Hackney v. McKenney, 113 Fla. 176, 151 So. 524 (1933). We held in West Virginia Hotel Corporation v. W.C. Foster Co., 101 Fla. 1147, 132 So. 842 (1931), citing City of Tampa v. Palmer, 89 Fla. 514, 105 So. 115 (1925): "* * * if the over-valuation was the result of mere inadvertence or bona fide mistake of judgment, the remedy of the taxpayer is to go before the administrative body provided for the equalization of tax assessments, unless the valuation is so flagrantly and obviously excessive as within itself to amount to a fraud, and clearly imputes to the tax assessor an intention to arbitrarily discriminate against the complaining taxpayer."

As previously stated the good faith of the taxing authorities is not questioned. The inequalities resulting from the assessments are a result of reliance upon the ultra vires and void tax exemption contracts between the City and the developers. Only "[W]here there is an intentional, arbitrary, and systematic undervaluation by tax officials of some of the taxable property in the same class with other property, it contravenes the constitutional rights of one whose property is intentionally and arbitrarily overvalued," and further "* * * it is held that mere errors of judgment by officials will not support a claim of discrimination. There must be something more — something which in effect amounts to an intentional violation of the essential principle of practical uniformity that good faith of such officers and the validity of their actions are presumed. When assailed, the burden of proof is upon the complaining party." Camp Phosphate Co. v. Allen, 77 Fla. 341, 81 So. 503 (1919). See also Folsom v. Bank of Greenwood, 97 Fla. 426, 120 So. 317 (1929).

We construe F.S. § 192.21, F.S.A. relative to the correction of acts of omission or commission on the part of tax assessors at any time as relating to the effect of the validity of the lien of the taxes assessed. Here the validity of the lien of taxes assessed in years prior to 1963 has not been raised and the taxes have been paid.

Although back assessments are specifically authorized by F.S. § 193.23, F.S.A. equitable estoppel would prevent the City in this case where good faith is not disputed from back assessment of taxes for the years 1959, 1960 and 1961. The city has affirmatively acted in assessing taxes as agreed under the contracts with the various developers over a period of years and it is reasonable to believe that the developers have long acted in reliance thereupon. Where the taxing authority is in full possession of all pertinent facts it is better to impose the burden upon it to exercise care than to create uncertainty as to the tax status of property for prior years. Compare Coppock v. Blount, 145 So.2d 279 (Fla.App. 3d Dist. 1962); Sharrow v. City of Dania, Fla. 1955, 83 So.2d 274; City of Miami Beach v. 8701 Collins Avenue, Inc., Fla. 1955, 77 So.2d 428; and Texas Co. v. Town of Miami Springs, Fla. 1950, 44 So.2d 808.

The other questions have been examined and found to be without merit, so the judgment of the lower court is

Affirmed.

THOMAS, Acting C.J., and DREW, O'CONNELL and CALDWELL, JJ., concur.

ERVIN, J., concurs specially with opinion.

HOBSON (Ret.), J., concurs specially and agrees with ERVIN, J.