In its purported capacity as agent for certain property owners, Southern Tax Consultants, Inc. (STC) presented for filing real property tax returns. DeKalb County Tax Commissioner Tom Scott refused to accept the returns, on the ground that STC had not submitted sufficient proof of its agency relationship with the property owners. STC then brought this mandamus action to compel Commissioner Scott to accept the returns. The trial court denied mandamus relief, and STC appeals.
OCGA § 48-5-15 (a) expressly authorizes the return of real property “by the person owning the real property or by his agent. . . .” (Emphasis supplied.) Since an agent is authorized to file a property tax return, tax officials must insure that a purported agent who attempts to file a return of real property is, in fact, authorized to act for the owner thereof. Prohibiting tax officials from requiring proof of agency would severely limit not only their initial ability to identify unauthorized returns, but also their subsequent ability to prove agency should that become necessary. OCGA § 48-5-19 requires that an oath be given by the purported agent. However, this oath, standing alone, would not constitute proof of agency against the property owner. It has long been the law of this state that the out-of-court declarations of a purported agent do not, without more, prove the existence of an agency relationship.
“The agent certainly can not confer authority upon himself. Evidence of his own statements or admissions, therefore, is not admissible against his principal for the purpose of establishing, enlarging, or renewing his authority; nor can his authority be established by showing that he acted as agent or that he claimed to have the powers which he assumed to exercise.” [Cits.]
Jones v. Harrell, 110 Ga. 373, 380 (4) (35 SE 690) (1900). The purported agent’s out-of-court declarations are admissible only in corroboration of other competent evidence tending to establish the fact of agency. Cambron v. Cogburn, 116 Ga. App. 373 (1) (157 SE2d 534) (1967). Since the out-of-court oath required by OCGA § 48-5-19 is made by the purported agent himself, unless Commissioner Scott requires some additional proof of STC’s agency at the outset, he would be at an evidentiary disadvantage in attempting to prove STC’s agency should it later become necessary to bind the property owner to the representations in the return or to show the sufficiency of notice to the property owner. See Davis v. Metropolitan Life Ins. *348Co., 196 Ga. 304, 321 (3) (26 SE2d 618) (1943) (tax assessor could not prove agency by the out-of-court declarations of the alleged agent). Compare Terminal Transport Co. v. Decatur Truck &c. Co., 90 Ga. App. 859, 864 (84 SE2d 494) (1954) (agency proved by in-court sworn testimony of purported agent).
No statute affirmatively authorizes tax officials to require proof of the purported agent’s authority to act for the owner. However, no statute affirmatively precludes tax officials from doing so. By statute, Commissioner Scott is authorized to perform all duties “the law requires and which necessarily under the law appertain to [his] office. . . .” OCGA § 48-5-103 (10). According to Commissioner Scott’s oath of office, he “will before receiving returns carefully examine each.” OCGA § 48-5-101. In performance of this duty, Commissioner Scott undoubtedly has discretion to reject unsigned returns. Accordingly, we hold that, in the performance of this duty, Commissioner Scott likewise has the discretion to reject tax returns signed by a person other than the owner, absent proof of authorization.
“Mandamus will not be granted when the performance which was sought as an official duty can not be compelled under applicable statutory law.” State of Ga. v. Johnson, 214 Ga. 607 (106 SE2d 353) (1958). Applicable statutory law does not require tax officials to accept property tax returns from purported agents without proof of agency. STC submitted no proof of agency with the returns which it presented for filing. Accordingly, the trial court correctly denied STC’s petition for mandamus. See Douglas v. Gibbs, 147 Ga. 39 (1) (92 SE 754) (1917).
Judgment affirmed.
All the Justices concur, except Sears, J, who dissents.