The subjects of taxation are as various as the purposes for which taxes may be levied, and the largest discretion is allowed to the legislative power in determining the basis on which taxes shall be imposed. Universally those owning property, whether tangible or intangible, are required to pay taxes in some proportion in accordance with the value of the property thus owned. Taxes may be levied on real property or personal property, on occupations, on incomes, on inheritances, and on various other rights, benefits, and privileges which are enjoyed under the protection and sanction of organized society. Per capita taxes, usually called poll taxes, are also levied, but it is not usual to attempt to raise any considerable general revenue in that manner.

Where it is attempted to levy a tax upon property, the property must be in some sense within the jurisdiction of the taxing power. Thus real property may be taxed in the state within which it is situated, but not in another state. Personal property may be taxed where the owner resides, for property of that character is presumed to be under the possession and control of the owner at the place of his domicile. Thus an individual may be taxed in the state of his residence upon his moneys and credits, including notes, bonds, and other forms of indebtedness which he owns, even though such notes and bonds are secured by mortgage on property situated elsewhere. On the other hand, personal property may be taxed in the state in which it is actually situated and held, though the owner may reside in another state (New Orleans v. Stempel). This may result in double taxation, that is, in the case of personal property the owner may be taxed on such property where he resides, though the property itself is in another state, and the state in which the property actually is may levy taxes thereon regardless of the fact that the owner lives and is taxed on such property in another state. It is, of course, inequitable that the owner of property should be compelled to pay taxes thereon in two distinct jurisdictions, but it is impracticable entirely to avoid such results under present methods of taxation.

Double taxation also results from the levying of taxes on real property for its full value in the state where the property is situated, while one to whom the owner owes indebtedness secured by mortgage on the property is also taxed on the notes evidencing such indebtedness and the mortgages given to secure them; but it seems to be impracticable to avoid such a result without, in some cases, allowing persons to escape taxation on property with which they are justly chargeable. Perfect equality and equity as to the burdens of taxation cannot be attained, and the best that can be done is to adopt such a basis for the levying of taxes and such methods for their collection as shall on the one hand afford necessary public revenue, while on the other they are apportioned as fairly and justly as may be among the persons and property subject to the taxing power.

But taxes cannot be imposed upon property which is in no sense within the jurisdiction of the taxing power. If neither the property nor the owner is within the state, then no tax can be imposed by the state. For instance, it has been held in Murray v. Charleston that if municipal bonds are owned by a non-resident of the state, the legislature cannot authorize the municipality issuing and under obligation to pay interest on such bonds to deduct a portion of the interest by way of taxes as against the non-resident owner of the bonds. For similar reasons the state in which is situated real property that is mortgaged to a non-resident cannot require that a part of the interest on the mortgage indebtedness be paid by the debtor to the state by way of tax against the non-resident owner (State Tax on Foreign-Held Bonds). But there seems to be no legal objection to requiring a non-resident mortgagee to pay taxes on his interest in the mortgaged real property where the property is situated. (See Savings Society v. Multnomah County.)