It's worth remembering that the tax code is progressive, so your marginal tax rate is the top tax rate you pay — the rate you would pay on
an additional dollar of income.
The tax credits «phase - out» within certain income ranges, with their value dropping with
each additional dollar of income.
A marginal tax rate is the amount of tax paid on
an additional dollar of income.
It's worth remembering that the tax code is progressive, so your marginal tax rate is the top tax rate you pay — the rate you would pay on
an additional dollar of income.
US income tax works this way: it is a marginal tax, i.e. the tax is calculated from
each additional dollar of income, according to the following rule: there's a number of «brackets», and once you income is in certain bracket, the additional dollars are taxed according to this bracket, until you have enough income to go to higher bracket.
Marginal tax rate is best defined as the amount of tax you pay on
an additional dollar of income and the United States uses multiple increasing rates for specific ranges of income.