Tax Deduction

An expense that reduces your taxable income — saving you money at your marginal tax rate, not dollar-for-dollar.

A tax deduction reduces the amount of income subject to taxation. If you're in the 22% federal bracket and claim a $1,000 deduction, you reduce your tax bill by $220 — not $1,000. This is the key distinction from a tax credit, which reduces your tax bill dollar-for-dollar. Deductions are valuable, but their value scales with your tax bracket: the same deduction is worth more to a high earner in a 37% bracket than to someone in a 12% bracket.

The IRS offers two main paths for deductions on your federal return: the standard deduction (a flat amount based on filing status, $14,600 single / $29,200 married for 2024) or itemized deductions (a sum of qualifying individual expenses). You choose whichever is larger. Since the Tax Cuts and Jobs Act of 2017 significantly raised the standard deduction, the majority of filers now take the standard deduction and don't itemize.

Above-the-line deductions (also called adjustments to income) are particularly valuable because they reduce AGI regardless of whether you itemize. These include traditional 401(k) and IRA contributions, HSA contributions, student loan interest, self-employed health insurance, and alimony (for pre-2019 agreements). Below-the-line deductions are only useful if you itemize and exceed the standard deduction threshold — these include mortgage interest, state and local taxes (SALT, capped at $10,000), charitable contributions, and medical expenses above 7.5% of AGI.

High-Value Deductions for Employees

  • Traditional 401(k): up to $23,000/year (2024); reduces taxable income dollar-for-dollar at your marginal rate.
  • HSA contributions: up to $4,150 single / $8,300 family (2024); fully deductible, triple tax-advantaged.
  • Traditional IRA: up to $7,000/year (2024); deductibility phases out at higher incomes if you have a workplace plan.
  • Student loan interest: up to $2,500/year, phases out at higher incomes.
  • Self-employed health insurance: 100% of premiums deductible as above-the-line adjustment.
  • Charitable contributions: deductible when itemizing; donating appreciated stock avoids capital gains and gets a full FMV deduction.

Deduction vs Credit: The Key Difference

  • Deduction: reduces taxable income → saves you (marginal rate × deduction amount).
  • Credit: reduces tax owed directly → saves you (full credit amount), regardless of tax bracket.
  • Example: $1,000 deduction at 22% marginal rate saves $220. A $1,000 tax credit saves $1,000.
  • Non-refundable credit: can reduce your tax to zero but not below — you don't get the excess back.
  • Refundable credit: can reduce your tax below zero and result in a refund (e.g., Earned Income Tax Credit).
  • This is why high-income earners often prefer deductions (their marginal rate is high), while lower-income earners benefit more from credits.

Example

A freelancer in the 24% bracket spends $2,000 on a home office, $800 on software subscriptions, and $1,500 on professional development — all legitimate business deductions on Schedule C. Her taxable self-employment income is reduced by $4,300, saving her roughly $1,032 in federal income tax plus a portion of self-employment tax.