It will add to clearness of the subject, if, at the outset, we distinguish between a tax and two other revenues that resemble taxes. "A tax is a payment, usually in money, exacted by the government for the purpose of carrying on public enterprises for the common good." It will be noticed that payment is compulsory, and that expenditures are made for the benefit of society as a whole. Examples are the general property tax, income and inheritances taxes, and excises. Resembling a tax somewhat are the special assessment and the fee. As its name suggests, the special assessment is levied for the purpose of defraying a special public charge. Professor Seligman defines it as "a payment made once for all to defray the cost of a specific improvement to property undertaken in the public interest, and levied by the government in proportion to the particular benefit accruing to the property owner." Of the several kinds of special-assessment enterprises the best-known is the construction of city pavements. The same authority defines a fee as "a payment to defray the cost of each recurring service undertaken by the government primarily in the public interest, but conferring a measurable special advantage on the fee payer." The principle underlying the fee is public regulation, though individuals that pay it are usually benefited. Fees are charged for marriage licenses, for recording of deeds, and for numerous other public services of like nature.