marginal rate
noun [ C ]
ukus(also marginal tax rate); (marginal rate of tax) ACCOUNTING, TAX
the rate of tax paid on the last part of a person's or organization's income in a particular period:
The law would have lowered the top marginal rate on income earned in the city.
The higher marginal tax rate applies to individuals with more than $120,000 of net income.
For most people, their marginal rate of tax will be higher when investing and lower when retired.