What a tax write-off actually is

A tax write-off is an expense you subtract from your income before calculating how much tax you owe. The IRS calls this a deduction. When you deduct $1,000, you reduce your taxable income by $1,000 — which means you pay tax on less money overall.

The difference between a write-off and a tax credit is important: a write-off lowers your income, while a tax credit directly reduces the tax you owe. A $1,000 deduction might save you $200 or $300 in taxes depending on your tax bracket. A $1,000 credit saves you exactly $1,000 in taxes.

You can only deduct expenses that the IRS allows. The IRS publishes lists of what counts — medical bills over a certain threshold, mortgage interest, charitable donations, business expenses, and others. If an expense is not on the IRS list, you cannot deduct it, even if it feels like it should count.

Key Takeaways

  • A tax write-off reduces your taxable income, which lowers the total tax you owe, but the savings depend on your tax bracket.
  • You can only deduct expenses the IRS specifically allows — common ones include mortgage interest, charitable donations, medical costs above a threshold, and business expenses.
  • Most people use the standard deduction (a fixed amount set by the IRS each year) rather than itemizing individual deductions.
  • To claim a deduction, you must keep receipts and records; the IRS can ask you to prove any deduction you claim.
  • Self-employed people and business owners can deduct more types of expenses than wage earners, including home office costs and vehicle mileage.

Standard deduction versus itemizing

The IRS gives you two paths: take the standard deduction or itemize. The standard deduction is a flat dollar amount that changes each year. For 2024, it is $14,600 for single filers and $29,200 for married couples filing jointly. You do not have to prove anything — you just subtract that amount from your income.

Itemizing means you add up all your individual deductions (mortgage interest, property taxes, charitable donations, medical expenses, and so on) and use that total instead of the standard deduction. You only itemize if your total deductions exceed the standard deduction. Most people do not itemize because their deductions do not add up to more than the standard amount.

If you itemize, you must keep records of every deduction. The IRS does not ask for them when you file, but if you are audited, you have to produce receipts, bank statements, or other proof that the expense happened and was deductible.

Common deductions for wage earners

If you work for an employer and receive a W-2, your deduction options are limited. You can deduct mortgage interest and property taxes on your home (up to $750,000 of mortgage debt and $10,000 in state and local taxes combined). You can deduct charitable donations to registered nonprofits. Medical expenses that exceed 7.5% of your adjusted gross income can be deducted.

Student loan interest up to $2,500 per year is deductible even if you do not itemize — this is called an "above-the-line" deduction. Contributions to a traditional IRA (up to $7,000 in 2024, or $8,000 if you are 50 or older) are also deductible above-the-line if your income is below certain thresholds.

Most other expenses — work clothes, commuting costs, job training — are not deductible for wage earners. The rules changed in 2017 and have not shifted back.

Deductions for self-employed people and business owners

If you are self-employed or own a business, you can deduct far more. You can write off the cost of supplies, equipment, rent or mortgage on a workspace, utilities, internet, phone bills, insurance, vehicle mileage (you deduct either actual mileage at the IRS rate or a standard mileage rate — 67 cents per mile in 2024 for business use), and wages you pay employees.

You can also deduct a portion of your home if you use part of it exclusively for business. This is called the home office deduction. You calculate it either by the simplified method (multiply your office square footage by $5 per square foot, up to 300 square feet) or by tracking actual expenses like rent, utilities, and depreciation.

Business meals and entertainment are partially deductible — 50% of meal costs if you are discussing business, though the rules tightened after 2017. Professional services like accounting and legal fees are fully deductible. The key rule: the expense must be ordinary and necessary for your business to operate.

What you need to keep as proof

The IRS does not require you to send receipts with your tax return, but you must keep them for at least three years in case of an audit. For large deductions or if you are self-employed, keep records for at least six years. The IRS can go back further if it suspects fraud.

What counts as proof depends on the deduction. For charitable donations under $250, a bank statement or receipt from the charity is enough. For donations over $250, you need a written acknowledgment from the charity. For medical expenses, keep the bill and proof of payment. For business expenses, keep receipts, invoices, and mileage logs.

If you lost a receipt, a credit card statement showing the charge can sometimes substitute, though it is weaker proof. For mileage, keep a log showing the date, destination, business purpose, and miles driven. A single entry in a notebook is not enough — the IRS wants contemporaneous records, meaning you wrote them down at the time, not months later.

How deductions affect your tax bracket

The amount you save from a deduction depends on your tax bracket. The U.S. uses a progressive tax system: different portions of your income are taxed at different rates. In 2024, single filers pay 10% on income up to $11,600, then 12% on income from $11,601 to $47,150, and so on up to 37% on income over $578,100.

If you are in the 22% bracket and you deduct $1,000, you save $220 in federal tax. If you are in the 12% bracket, you save $120. This is why a deduction is worth less to lower-income people than to higher-income people — the math is built into the system.

State and local taxes work the same way. If your state income tax rate is 5%, a $1,000 deduction saves you $50 in state tax on top of the federal savings.

Deductions you cannot claim

The IRS does not allow deductions for personal expenses, even if they feel work-related. You cannot deduct commuting costs, work clothes (unless they are specialized like a police uniform), haircuts, gym memberships, or tuition for a degree that qualifies you for a new career. You cannot deduct the cost of raising children, pet care, or home repairs.

Fines and penalties are not deductible. Gambling losses can only offset gambling winnings, not other income. Gifts to individuals are not deductible (gifts to registered charities are). Political donations are not deductible. Life insurance premiums are not deductible.

The rule of thumb: if it is a personal living expense, it is not deductible. If it is an ordinary and necessary business expense, it usually is.

Frequently Asked Questions

Can I deduct my home internet if I work from home?

Only if you are self-employed or own a business. If you work for an employer, you cannot deduct internet or other home office expenses. If you are self-employed, you can deduct a portion of your internet bill proportional to the percentage of your home used for business — for example, if your office is 10% of your home's square footage, you can deduct 10% of your internet bill.

What if I do not have a receipt for a deduction?

A credit card statement or bank statement showing the charge can work as backup proof, though it is weaker than a receipt. For large deductions, the IRS prefers the original receipt. If you genuinely lost it, document what you remember and keep the statement. If audited, explain what happened — the IRS sometimes accepts reasonable explanations, but there is no may provide.

Can I deduct my car payment?

No. You can deduct mileage driven for business purposes at the IRS standard rate (67 cents per mile in 2024), or you can deduct actual expenses like gas, insurance, and maintenance if you track them. You cannot deduct the car payment itself or depreciation unless you own a business and use the actual expense method rather than mileage.

Do I have to itemize to get any deductions?

No. Some deductions are "above-the-line," meaning you can claim them whether you itemize or take the standard deduction. Student loan interest, IRA contributions, and educator expenses are above-the-line. Most other deductions require you to itemize, which only makes sense if your total deductions exceed the standard deduction.

What happens if I claim a deduction I am not supposed to?

If the IRS audits you and finds a deduction you cannot prove or are not allowed to claim, you have to pay back the tax you saved plus interest. If the IRS determines you were careless, you may owe a penalty on top of that. If it looks intentional, the penalty is higher. Keep good records to avoid this situation.