What is a tax write-off?

A write-off lowers your taxes, but not by as much as many people think. Here's how deductions and credits work, what each is worth, and which ones you can actually use.

By the Calcist team · Updated October 29, 2026 · About a 5-minute read

What "write-off" means

A tax write-off is anything that lowers your tax bill. In everyday use it usually means a deduction: an amount you subtract from your income before tax is figured. People also use it loosely for credits, which come straight off the tax itself. The difference matters, because a $1,000 deduction and a $1,000 credit are worth very different amounts.

Deductions vs credits

	Deduction	Credit
What it reduces	Your taxable income	Your tax, dollar for dollar
What $1,000 is worth	$1,000 × your top tax rate: $220 in the 22% bracket	$1,000
Examples	Standard deduction, student loan interest, mortgage interest, business expenses	Child Tax Credit, education credits, Earned Income Tax Credit

Tax saved by a deduction = deduction × your marginal tax rate
Tax saved by a credit = the credit (refundable credits can go beyond zero tax)

For example, a single filer with $70,000 of taxable income in 2026 is in the 22% bracket (taxable income over $50,400). A $1,000 deduction lowers taxable income to $69,000 and saves $220. A $1,000 credit saves the full $1,000.

The three kinds of deductions

Adjustments ("above the line"). These come off your income before AGI is figured, so you get them whether or not you itemize: deductible IRA contributions, HSA contributions, student loan interest (up to $2,500), half of self-employment tax and more. Lowering AGI can also help you qualify for other breaks. The AGI calculator walks through them.

The standard deduction or itemized deductions. You take the larger of the two. The 2026 standard deduction is $16,100 single, $32,200 married filing jointly and $24,150 head of household. Itemized deductions include state and local taxes (capped at $40,000 for 2025 and $40,400 for 2026), mortgage interest and charitable gifts. Most people get more from the standard deduction, so extra mortgage interest or a donation often doesn't change their tax at all. Compare yours with the standard vs itemized calculator.

Other deductions on top. For 2025 through 2028, new deductions on Schedule 1-A are available whether or not you itemize: up to $25,000 of qualified tips, up to $12,500 of qualified overtime pay ($25,000 joint), up to $10,000 of interest on a qualifying new car loan, and $6,000 for each person 65 or older. Each has income limits.

Business write-offs

If you're self-employed, ordinary and necessary business costs (supplies, software, a share of your phone, business mileage) are subtracted on Schedule C. That lowers both income tax and the 15.3% self-employment tax, so a business write-off can be worth more than a personal one. It still isn't free money: spending $1,000 to save about $300 leaves you $700 poorer. The 1099 tax calculator shows the effect on freelance income.

Credits

Credits are usually aimed at families, students and lower earners. For 2025 the Child Tax Credit is up to $2,200 per child under 17, and up to $1,700 of it is refundable, meaning you can get it back even if you owe no tax. Nonrefundable credits can only bring your tax down to zero.

Common mix-ups

"It's a write-off, so it's free." A deduction only returns your tax rate times the cost.
"I can deduct my donation." Only if you itemize, except that from 2026 non-itemizers can deduct up to $1,000 ($2,000 joint) of cash gifts.
"Deductions lower my Social Security and Medicare tax." Personal deductions don't; only business expenses on Schedule C reduce self-employment tax.

Sources

IRS Rev. Proc. 2025-32 (2026 inflation adjustments) – 2026 brackets and standard deduction
2025 Schedule 1 (Form 1040) – adjustments to income
2025 Schedule 1-A (Form 1040) – tips, overtime, car loan interest and senior deductions
IRS Topic 456, Student loan interest deduction – $2,500 student loan interest
IRS: Correction to the SALT deduction amount in the 2026 Form 1040-ES – $40,400 SALT cap for 2026
IRS Tax Tip 2026-17: Tax benefits for parents and families – $2,200 Child Tax Credit, $1,700 refundable
2026 Form W-4 – 2026 charity deduction for non-itemizers

General information for tax years 2025 and 2026, not tax advice. Figures come from the IRS, SSA and state sources listed above.

Questions people ask

What is a tax write-off?

Anything that lowers your tax, most often a deduction that reduces your taxable income. A deduction saves your tax rate times its amount; a credit cuts your tax dollar for dollar.

What does write it off mean for a business?

Deducting a business expense from business income on Schedule C, which lowers both income tax and self-employment tax.

Is a tax credit better than a deduction?

Dollar for dollar, yes. A $1,000 credit saves $1,000; a $1,000 deduction saves $100 to $370 depending on your bracket.

Can I write off things if I take the standard deduction?

Yes, some. Adjustments like IRA, HSA and student loan interest, the 2025–2028 Schedule 1-A deductions, and business expenses don't require itemizing.

Related calculators

Standard vs itemized deduction calculator2025 and 2026 standard deduction vs your itemized total.AGI calculatorAdjusted gross income and taxable income, line by line.Income tax calculator2026 federal income tax, brackets, marginal and effective rate.1099 tax calculatorFreelance tax on 1099 income and how much to set aside.