Marginal Tax Rate
Definition
The tax rate applied to your last dollar of taxable income. The US uses a progressive tax system with seven brackets: 10%, 12%, 22%, 24%, 32%, 35%, and 37%. Each bracket applies only to income within that range, not your entire income. Your effective (average) tax rate is always lower than your marginal rate.
Example
A single filer with $50,000 in taxable income pays 10% on the first $11,600, 12% on income from $11,601 to $47,150, and 22% on income from $47,151 to $50,000. Their effective rate is about 13.5%.