On May 26, 1950, Charles D. Red-wine, as State Revenue Commissioner for Georgia, assessed for ad valorem taxation certain real and personal property in this State belonging to the Georgia Railroad and Banking Company and notified the company that the assessment as made by him would become final after the expiration of thirty days there*262from- unless a written protest was filed thereto. The assessment so made was for the years 1939 to 1950, inclusive, and was for State, county, municipal, and school-district taxes at the rate fixed for all other like property in this State for each of the years mentioned. The company was also notified that appropriate adjustments would be made for the taxes which it had previously paid during the years involved at the rate of one-half of one percent of its net earnings. On June 22, 1950, the company filed a written protest, alleging that the assessment was illegal because its property was, for reasons therein stated, exempt from all ad valorem taxes. After a hearing, the commissioner sustained the validity of his assessmént and the company took an appeal to the Superior Court of Richmond County. By final decree that court likewise sustained the assessment as made, and the exception here is to that judgment.
It is argued by counsel for the plaintiff in error that the trial court had no jurisdiction to entertain an appeal in this case from the State Revenue Commissioner’s final decision. If that be true, the judgment complained of is a nullity and must be reversed. Code, § 110-709; Head v. Bridges, 67 Ga. 227; Fussell v. Dennard, 118 Ga. 270 (45 S. E. 247); Jones v. Smith, 120 Ga. 642 (48 S. E. 134); Franklin County v. Crow, 128 Ga. 458 (57 S. E. 784). The parties to litigation cannot give to a court jurisdiction of the subject matter of a suit when it has none by law; and when a trial court, in a case over which it has as to subject matter no jurisdiction, renders therein any judgment except one of dismissal, and the case is brought here for review upon a writ of error, this court will of its own motion reverse the judgment whether exception to it for want of jurisdiction in the court below be taken in the bill of exceptions or not. Smith v. Ferrario, 105 Ga. 51 (31 S. E. 38); O’Brien v. Harris, 105 Ga. 732 (31 S. E. 745); Cutts v. Scandrett, 108 Ga. 620 (34 S. E. 186); Kirkman v. Gillespie, 112 Ga. 507 (37 S. E. 714); Dix v. Dix, 132 Ga. 630, 633 (64 S. E. 790). And, in the circumstances of this case, it cannot be said that the plaintiff in error is by conduct estopped to assert the trial court’s lack of jurisdiction to entertain and render final judgment on its appeal thereto. “Jurisdiction of the subject matter of a suit cannot be conferred by agreement or consent, or be *263waived or based on an estoppel of a party to deny that it exists.” Langston v. Nash, 192 Ga. 427, 429 (15 S. E. 2d, 481), and the cases there cited.
The right of appeal from one court to another is not a common-law. right, but depends on statute; and the same authority which bestows it may likewise withhold or withdraw it. Griffin v. Sisson, 146 Ga. 661 (92 S. E. 278). Our Constitution of 1945 provides that the superior court shall have appellate jurisdiction “in all.such cases as may be provided by law,” and in DeLamar v. Dollar, 128 Ga. 57, 66 (57 S. E. 85), it was said: “The appellate jurisdiction of the superior court must be exercised, and can only be exercised, in such cases as are provided by law.” Therefore we must look to and find authority in our statutes for the right of appeal to the superior court in this case if it exists as counsel for the defendants in error insist. By Chapter 92-59 of the Code of 1933 all persons or companies owning or operating railroads, street railroads, suburban railroads, or sleeping cars; and all persons or companies, including railroads, doing an express, telephone, or telegraph business in this State are among those who were, required to make annual tax returns of all property owned by them, and located in this State, to the Comptroller-General. Code, § 92-5902. The Comptroller-General was required 'to carefully scrutinize the returns so made to him, and if in his judgment the property embraced therein was returned below its value, or .the return was false in any particular, or in any wise contrary to law, he was required within 60 days thereafter to correct it and assess the value, from any information he could obtain. Code, § 92-6001. Also, if the Comptroller-General found that any owner of such property had refused or failed to make a return of it for taxation, he was authorized by section 92-6103 of the Code, after giving the owner thereof 20 days notice in writing, to assess it for State, county, municipal and school district taxes, from the best information obtainable as to its value. However, no provision for an appeal from the assessment of the Comptroller General was provided for in either event; but if the owner of such property disputed his assessment as to taxability, by section 92-6104 of the Code he was permitted to raise that question by petition in equity in *264the Superior Court of Fulton County; and if dissatisfied with the assessment as to value, his remedy was by arbitration under section 92-6002 of the Code. And later, by section 80 of the reorganization act of 1931 (Ga. L. 1931, p. 33), the owner of such property was permitted to contest the question of its tax-ability by an affidavit of illegality. Code, § 92-7301. See also, in this connection, Hicks v. Stewart Oil Co., 182 Ga. 654 (4) (186 S. E. 802), and Carreker v. Green & Milam, 183 Ga. 864 (189 S. E. 836). The legislature, by an act approved January 3, 1938 (Ga. L., Ex. Sess. 1937-38, p. 77), created the State Department of Revenue and vested in a State Revenue Commissioner all of the powers and duties respecting taxation previously performed by the Comptroller-General. A State Board of Tax Appeals, consisting of the Comptroller-General, the Auditor and the Treasurer, ex officio, was created by the act, and section 19 thereof declares in part that, “The function of the Board of Tax Appeals shall be to review the assessments made by the State Revenue Commissioner when by such assessment, after hearing by the Commissioner or his regularly authorized employee or agent, any taxpayer may be aggrieved and petition for said review.” Section 45 of the act also provides that, “The findings by the Board of Tax Appeals shall not be final; but either party may appeal from any order, ruling, or finding of the said board to the superior court of the county of the residence of the taxpayer unless the taxpayer be a railroad or other public service corporation or non-resident, in which event the appeal of either party shall be to the superior court of the county in which is located its principal place of doing-business, or in which the chief or highest corporate officer, resident in this State, maintains his office.” Accordingly, by the act of 1938 provision was made by the legislature for a review of the decision of the Board of Tax Appeals (created by the act for the purpose of settling disputes as to valuation and taxability) by the superior court in a de novo investigation, when a dissatisfied taxpayer entered an appeal thereto from the board’s decision. See Columbus Mutual Life Ins. Co. v. Gullatt, 189 Ga. 747 (8 S. E. 2d, 38). But, except as shown above, the taxing act of 1938 made no provision for an appeal to the superior court for the review of any question. *265The legislature, however, in 1943 passed an act (Ga. L. 1943, p. 204), which in several respects materially changed the act of 1938. By Section 2 of it, all the sections in Chapter III of the act of 1938, which created the Board of Tax Appeals and defined its jurisdiction, were expressly repealed and new sections were enacted in lieu thereof. Concerning the right of appeal, Section 18 of the amending act of 1943 reads as follows: “Except as otherwise provided by this act, all matters, cases, claims and controversies, of whatsoever nature arising in the administration of the revenue laws, or in the exercise of the jurisdiction of the State Revenue Commissioner or the Department of Revenue, as conferred by this act, shall be for determination by the State Revenue Commissioner, subject to review by the courts as provided for by Section 45 of Chapter IV of this Act. The effect of this section shall be that, except as hereinafter provided, all final rulings, orders, and judgments of the State Revenue Commissioner shall be subject to appeal and review under Section 45 of this act in the same manner, under the same procedure, and as fully, as if same had been considered -and passed upon by the State Board of Tax Appeals.” But Section 19 of the amending act of 1943 expressly declares that “The provisions of the foregoing section with reference to reviewing assessments of the State Revenue Commissioner shall not apply to assessments for ad valorem taxation against any person, corporation or company which was required by Chapter 92-59 of the Code of 1933 to return his or its property for ad valorem taxation to the Comptroller-General and is now required by such Chapter and this act of January 3, 1938, to make such returns to the State Revenue Commissioner.” We can not agree with counsel for the defendants in error that the exception referred to in section 18 and expressly stated in section 19 of the amending act of 1943 has reference to an assessment of value only. An examination of the taxing act of 1938 discloses that the State Revenue Commissioner has power to determine the taxability of property as well as authority to fix its value for taxing purposes, and the act of assessing such property for taxation includes a determination of the former as well as an ascertainment of the latter. Forrester v. Pullman Co., 192 Ga. 221, 222 *266(15 S. E. 2d, 185). According to Black’s Law Dictionary (3d ed.), the word “assessment” when used in connection with the subject of taxation, includes all of the steps necessary to be taken in the legitimate exercise of the power to tax. Therefore it seems very clear to us, from the plain language employed, that the ¡legislature, by sections 18 and 19 of the amending act of 1943, provided for an appeal to the superior court, under the procedure prescribed by section 45 of the act of 1938, from any final ruling, order, or judgment of the State Revenue Commissioner, except any final ruling, order, or judgment of the commissioner respecting assessments for ad valorem taxation against any person, corporation, or company which was required by Chapter 92-59 of the Code of 1933 to return his or its property to the Comptroller-General for taxation, and who now by the act of 1938 is required to make such returns to the State Revenue Commissioner, among which are railroad companies. Consequently, we must and do hold that our statutes make no provision for an appeal to the superior court from the decision of the State Revenue Commissioner by a railroad company whose property has been assessed by the commissioner for ad valorem taxation. That being true, the Superior Court of Richmond County had no jurisdiction to entertain the appeal in this case; and the judgment complained of is for that reason a nullity and must be reversed.
Judgment reversed.
All the Justices concur, except Duck-worth, C.J., and Atkinson, P.J., who dissent. Pharr, Judge, concurs specially.