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 key rule: the IRS only lets you deduct expenses that are ordinary and necessary for earning income or that the tax code specifically allows. You cannot deduct personal expenses like groceries or car payments. You can deduct business supplies, mortgage interest, or charitable donations because the tax code says those count.

Most people use one of two paths: the standard deduction (a flat amount set by the IRS each year) or itemized deductions (adding up individual expenses). You pick whichever gives you the bigger tax break.

Key Takeaways

  • A tax write-off reduces your taxable income, which lowers the total tax you owe — it does not give you a refund by itself.
  • You can either take the standard deduction (a fixed amount) or itemize deductions (list specific expenses), but not both.
  • Common deductions include mortgage interest, property taxes, charitable donations, medical expenses above a threshold, and business expenses if you are self-employed.
  • Keeping receipts and records is the only way to prove a deduction if the IRS asks questions later.
  • The standard deduction changes every year and varies by filing status, so it may be larger than your itemized deductions.

Standard deduction versus itemizing

The standard deduction is a single number the IRS sets each year. For 2024, it ranges from $14,600 (single filers) to $29,200 (married filing jointly), but these amounts change annually. You subtract this one number from your income and move on — no receipts needed, no list required.

Itemized deductions mean you add up individual expenses: mortgage interest, property taxes, charitable donations, medical costs, and others. You report these on Schedule A and subtract the total from your income. Itemizing only makes sense if your total deductions exceed the standard deduction for your filing status.

Example: if you are single and the standard deduction is $14,600, but your mortgage interest, property taxes, and charitable donations add up to $18,000, you itemize. If they add up to $12,000, you take the standard deduction instead. Most people take the standard deduction because it is simpler and often larger.

Deductions for homeowners

If you own a home, you can deduct mortgage interest (the interest portion of your monthly payment, not the principal) and property taxes paid to your state or local government. These are among the most common itemized deductions.

There is a cap: your total deduction for state and local taxes (SALT) — which includes property tax, income tax, and sales tax combined — cannot exceed $10,000 per year. This limit has been in place since 2017 and applies whether you are married or single.

You cannot deduct homeowners insurance, mortgage principal, HOA fees, or home repairs and maintenance. You also cannot deduct property taxes on a second home or investment property using the same rules — those follow different rules depending on how you use the property.

Deductions for self-employed people and business owners

If you run a business or are self-employed, you can deduct ordinary and necessary business expenses. This includes office supplies, equipment, software subscriptions, vehicle mileage (at the IRS rate, which changes yearly), home office space, professional fees, and advertising.

The IRS defines "ordinary" as common in your industry and "necessary" as helpful to your business. You cannot deduct personal expenses even if you use them sometimes for work. A home office deduction requires that you use a specific room or area exclusively for business — not a kitchen table you also eat at.

Self-employed people report business income and expenses on Schedule C, then calculate a profit or loss. You can deduct half of your self-employment tax (Social Security and Medicare tax) on your main tax return. Keep receipts and mileage logs because the IRS asks for proof more often with business deductions than with other types.

Charitable donations and medical expenses

Donations to may have access to charities — religious organizations, nonprofits, schools, and others recognized by the IRS — are deductible if you itemize. You need a receipt or written acknowledgment from the charity for donations of $250 or more. For smaller donations, a bank record or receipt from the charity is enough.

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 only deduct medical expenses above $4,500. This high threshold means most people do not benefit from this deduction unless they had major medical events that year.

may have access to medical expenses include doctor and dentist visits, prescription medications, medical equipment, and some travel costs to receive care. They do not include cosmetic procedures, over-the-counter medications (with rare exceptions), or health club memberships.

Education-related deductions and credits

The student loan interest deduction lets you deduct up to $2,500 of interest paid on federal or private student loans, even if you do not itemize. This is a deduction "above the line," meaning it reduces your income before you choose between standard and itemized deductions.

The tuition and fees deduction allows up to $4,000 off your taxable income for may have access to education expenses at an accredited school. You cannot claim this and a tax credit (like the American Opportunity Credit) for the same student in the same year — you have to pick one.

Tax credits are different from deductions: a $1,000 credit reduces your tax bill by $1,000, while a $1,000 deduction reduces your taxable income. The American Opportunity Credit and Lifetime Learning Credit are credits, not deductions, and they often provide more tax savings than the deduction.

Deductions you might overlook

Unreimbursed employee business expenses used to be deductible, but that changed in 2017 and remains suspended. If your employer does not reimburse you for work supplies or travel, you generally cannot deduct those costs anymore.

Gambling losses are deductible, but only up to the amount of gambling winnings you report. If you won $500 at a casino and lost $800, you can deduct $500 in losses — not the full $800.

Tax preparation fees and fees paid to a tax professional are deductible if you itemize, though this deduction has been suspended in recent years. State and local income taxes paid (including estimated tax payments) count toward your $10,000 SALT cap if you itemize.

Record-keeping and common mistakes

The IRS does not require you to attach receipts to your tax return, but you must keep them for at least three years in case of an audit. For business deductions, keep receipts, invoices, mileage logs, and bank statements. For charitable donations over $250, keep the written acknowledgment from the charity.

A common mistake is deducting personal expenses disguised as business expenses. A home office must be used exclusively for business. A vehicle must be used primarily for business, and you track mileage separately from personal driving. The IRS scrutinizes these deductions more closely than others.

Another mistake is claiming deductions you are not may have access to to claim. You cannot deduct both the standard deduction and itemized deductions in the same year. You cannot deduct an expense twice. You cannot deduct a loss on the sale of a personal home (though you can exclude up to $250,000 in gain if you meet ownership and use tests).

Frequently Asked Questions

Can I deduct my car payment?

No. Car payments are not deductible for personal use. If you use your vehicle for business, you can deduct either actual expenses (gas, insurance, repairs, depreciation) or the standard mileage rate set by the IRS each year. You track business miles separately and deduct only that portion.

What if I donate items instead of money to charity?

You can deduct the fair market value of donated items — clothing, furniture, household goods — if you itemize and donate to a may have access to charity. You need a receipt from the charity listing what you donated. For items worth over $500, you must file Form 8283 with your tax return.

Do I need to itemize to deduct student loan interest?

No. Student loan interest is an "above the line" deduction, meaning you can claim it whether you take the standard deduction or itemize. The maximum deduction is $2,500 per year, and your income must be below a certain threshold to claim the full amount.

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

Only if you are self-employed and use a portion of your home exclusively for business. You calculate the percentage of your home used for business and deduct that same percentage of your internet bill. If you are an employee, you cannot deduct it.

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

If the IRS audits you and finds a deduction you cannot support with receipts or that does not may have access to, they will disallow it and you will owe back taxes plus interest. Penalties may explore if the error was intentional. Keep records for at least three years to avoid this situation.