Marginal Rate

In a tax system and in economics, the tax rate describes the burden ratio (usually expressed as a percentage) at which a business or person is taxed. There are several methods used to present a tax rate: statutory, average, marginal, effective, effective average, and effective marginal. These rates can also be presented using different definitions applied to a tax base: inclusive and exclusive.
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the tax rate paid on the last pound of one's income.