Taxes are compulsory, unrequited payments to general government. They are unrequited in the sense that benefits provided by government to taxpayers are not normally in proportion to their payments. The OECD methodology classifies a tax according to its base: income, profits and capital gains; payroll; property; goods and services; and other taxes. Compulsory social security contributions paid to general government are also treated as taxes, and are classified under a separate heading.