deduction
Something that lowers the income you get taxed on.
An amount subtracted from gross income in arriving at taxable income.
What that means in practice
A deduction does not cut your tax bill directly. It cuts the income the bill is calculated from. So a deduction is worth whatever tax you would have paid on that slice of income — which means the same deduction saves more for someone in a higher bracket than for someone in a lower one. That is the opposite of how a credit works.
Deductions reduce the base rather than the liability, so their value equals the deducted amount multiplied by the taxpayer's marginal rate. This makes them regressive in value relative to credits, which reduce liability directly and are therefore worth the same to every taxpayer who can use them. ⚠️ Above-the-line deductions reduce adjusted gross income and are available whether or not the taxpayer itemizes; below-the-line deductions are available only to itemizers.
Questions people ask
Who decides this — the federal government or my state?
Two governments, independently. The federal rule and your state's rule share a name and nothing else. So deduction can mean one thing on your federal return and another on the state one.
Do I need to understand other terms before this one makes sense?
It has neighbors. deduction connects to several other terms, listed below. Each carries part of the meaning. The word does not fully resolve on its own.
I have seen this called something else. Is it the same thing?
Probably yes. deduction travels under several names. Forms, employers and news coverage each tend to use a different one for the same rule. That is a real source of confusion, not a trivial one. The alternatives are listed on this page.
Why is this one harder to pin down than the others?
The rule is conditional rather than flat. That is why deduction takes more explaining here than the terms around it.
At which level of government is this determined?
Income tax concepts are defined independently at federal and state level. States may conform to the federal definition, conform selectively, or define their own; conformity is legislated and can be static (tied to a fixed date) or rolling. ⚠️ A federal change therefore propagates to some states automatically and to others only by subsequent state action.
What conceptual dependencies does this term carry?
This term has multiple conceptual dependencies, enumerated in the related-terms list. Definitions in tax law are frequently mutually referential — a provision's meaning depends on defined terms elsewhere in the code — so isolated reading commonly produces error.
What alternative designations refer to this concept?
This concept is referred to by multiple designations across statutory text, agency guidance, payroll documentation and common usage. The alternatives are enumerated on this page. ⚠️ Terminology divergence is a frequent source of error where a statutory term and its colloquial equivalent are not exactly co-extensive.
Why does this term require extended treatment?
This provision carries conditional application — its effect depends on filing status, income level, timing or jurisdiction — so a single-sentence definition necessarily omits determinative conditions. The extended treatment on this page states them explicitly rather than compressing them away.