What is Tax Deduction?
A deduction lowers the income you're taxed on. Its value depends on your bracket — it saves you the rate, not the full amount.
How it works
You subtract deductions before the brackets apply, so a deduction shrinks taxable income. A dollar deducted saves you a dollar times your marginal rate. That's why the same deduction is worth more to a high earner than a low one.
A quick example
What people get wrong
"Write it off" doesn't mean it's free. A $100 deductible expense might save you $22 in tax — you still spent $78. Deductions soften real costs; they don't erase them.