A tax write-off is an expense you subtract from your income to lower your taxable income

When you have a tax write-off — also called a deduction — you reduce the amount of income the IRS taxes you on. If you earn $60,000 and have $10,000 in deductions, you pay tax on $50,000 instead. The tax you save depends on your tax bracket: someone in the 22% bracket saves $2,200 on that $10,000 deduction, while someone in the 12% bracket saves $1,200.

Not every expense you pay counts as a write-off. The IRS allows deductions only for certain categories: mortgage interest, state and local taxes up to $10,000 per year, charitable donations, medical expenses above 7.5% of your income, business expenses if you're self-employed, and a few others. Personal expenses — groceries, gas, clothing — do not count, even if you had to pay them.

You have two paths to deductions: the standard deduction or itemized deductions. Most people take the standard deduction, a flat amount the IRS sets each year (for 2024, it's $14,600 for single filers and $29,200 for married filing jointly). If your itemized deductions add up to more than the standard deduction, you can itemize instead and deduct each expense separately. You pick whichever is larger.

Key Takeaways

  • A tax write-off reduces your taxable income, which lowers the tax you owe; the actual tax savings depends on your tax bracket.
  • Only certain expenses count as deductions: mortgage interest, charitable gifts, medical costs above a threshold, business expenses, and state and local taxes up to $10,000 per year.
  • You can either take the standard deduction (a fixed amount) or itemize deductions (add up individual expenses), whichever gives you a larger total.
  • To claim itemized deductions, you must keep receipts and documentation for each expense and report them on Schedule A of your tax return.

Standard deduction versus itemizing: which saves you more

The standard deduction is simpler: you claim one number and move on. You do not need receipts or records. For 2024, the standard deduction is $14,600 (single), $29,200 (married filing jointly), $21,900 (head of household), and $14,600 (married filing separately). These amounts increase slightly each year for inflation.

Itemizing means adding up your individual deductions — mortgage interest, property taxes, charitable donations, medical expenses, and others — and reporting them on Schedule A of Form 1040. You itemize only if your total exceeds the standard deduction. For example, if you're single with $18,000 in itemized deductions, you itemize and deduct $18,000 instead of the standard $14,600, saving tax on an extra $3,400 of income.

Most people benefit from the standard deduction because it is high enough that their actual deductions do not exceed it. Itemizing makes sense if you have a mortgage with significant interest, live in a high-tax state, made large charitable donations, or had major medical expenses in one year. Run both numbers on your tax return software or with a tax professional to see which is larger.

Common deductions you can claim

If you itemize, mortgage interest is often the largest deduction. You can deduct interest on up to $750,000 of mortgage debt (or $375,000 if married filing separately). Property taxes on your home are deductible, but combined with state income tax, your total state and local tax deduction is capped at $10,000 per year — this limit applies whether you're single or married.

Charitable donations to may have access to organizations (churches, nonprofits, schools) are deductible if you itemize. You need a receipt or written acknowledgment from the charity. Donations of goods (clothing, furniture) are deductible at fair market value, not what you paid for them, and you should photograph the items and keep a list.

Medical and dental expenses are deductible, but only the amount that exceeds 7.5% of your adjusted gross income (AGI). If your AGI is $60,000, you can deduct medical expenses only above $4,500. This threshold is high enough that most people do not benefit unless they had a major surgery, ongoing treatment, or significant out-of-pocket costs in one year.

If you are self-employed, you can deduct business expenses: office supplies, equipment, mileage, home office rent or depreciation, professional services, and others. You report these on Schedule C. The key rule is that the expense must be ordinary and necessary for your business — not personal.

How to track and document deductions

If you itemize, keep receipts and statements for every deduction you claim. The IRS does not require you to attach them to your return, but you must have them if you're audited. For mortgage interest and property taxes, your lender and local assessor send you statements (Form 1098 for mortgage interest, property tax statements from your county). For charitable donations, keep the charity's receipt or a bank statement showing the transfer.

For medical expenses, keep receipts from doctors, hospitals, pharmacies, and insurance companies. For business expenses, keep invoices, credit card statements, and mileage logs. If you claim a home office deduction, measure the square footage and document your rent or mortgage payment and utilities.

Use a spreadsheet or tax software to organize deductions by category as the year goes on. This makes it easier to total them in December and decide whether to itemize. Many tax software programs (TurboTax, H&R Block, TaxAct) have sections to enter itemized deductions and will calculate whether itemizing or taking the standard deduction saves you more.

When bunching deductions makes sense

If your deductions are close to the standard deduction, you might benefit from bunching — timing large expenses to fall in the same tax year so your total exceeds the standard deduction. For example, if you usually have $12,000 in deductions but are planning a $5,000 charitable donation, you could make the donation in December of one year (bringing your total to $17,000, above the $14,600 standard) and skip donations the next year. This way you itemize one year and take the standard deduction the next, saving more tax overall than spreading donations evenly.

Bunching works best with charitable donations, which you control the timing of, and sometimes with medical expenses or property tax payments. It does not work with mortgage interest or most business expenses, which you cannot easily shift between years. Talk to a tax professional if your deductions are within a few thousand dollars of the standard deduction — they can model whether bunching would help.

Deductions versus credits: the difference

A deduction reduces your taxable income. A tax credit reduces your tax bill directly, dollar for dollar. A $1,000 deduction in the 22% bracket saves you $220 in tax. A $1,000 credit saves you $1,000 in tax. Credits are more valuable, but they are available only for specific situations: the Earned Income Tax Credit (EITC), the Child Tax Credit, education credits, and others.

You can claim both deductions and credits on the same return. Deductions lower your taxable income first, then credits reduce your tax. If you owe no tax after deductions, some credits (like the EITC) can give you a refund even if you had no tax withheld. Check whether you may have access to for any credits before filing — they often go unclaimed because people do not know they exist.

Frequently Asked Questions

Can I deduct my car payment or car insurance?

No, unless you use the car for business. If you are self-employed and use your car for work, you can deduct either actual expenses (gas, insurance, maintenance, depreciation) or the standard mileage rate (73 cents per mile for 2024). You must track business miles separately from personal miles.

What if I do not have a receipt for a charitable donation?

For donations under $250, a bank statement or receipt from the charity is enough. For donations of $250 or more, you need a written acknowledgment from the charity stating the amount and whether you received anything in return. Ask the charity for this letter before you file your return.

Can I deduct my student loan interest?

Yes, up to $2,500 per year, and you do not have to itemize to claim it. This is an "above-the-line" deduction, meaning it reduces your taxable income even if you take the standard deduction. Your loan servicer sends you Form 1098-E showing the interest you paid.

Do I have to itemize if I own a home?

No. Even if you own a home and pay mortgage interest and property taxes, you should compare your total itemized deductions to the standard deduction. Many homeowners still benefit from the standard deduction because the $10,000 cap on state and local taxes limits how much they can deduct.

What happens if I claim a deduction I should not have?

If the IRS audits you and finds a deduction you cannot document or that does not may have access to, they will disallow it and you will owe back taxes plus interest. If the error was unintentional, you usually avoid penalties. If it was intentional or reckless, penalties can be 20% or more of the unpaid tax. Keep good records to avoid this.