What Form 1040 is and who has to file it

Form 1040 is the main federal income tax return that the IRS uses to collect tax from you and determine whether you owe money or will receive a refund. Nearly every person who earned income in the past year and meets certain thresholds files this form — either on paper or through tax software. The IRS publishes a new version each tax year with small changes to line numbers and instructions.

You must file Form 1040 if your income exceeds the filing threshold for your age and filing status. For the 2023 tax year (filed in 2024), a single person under 65 must file if they earned more than $13,850 in wages. The threshold is higher if you're 65 or older, and it varies by filing status — married filing jointly, head of household, and so on. Even if you earned less than the threshold, you may want to file anyway if you had taxes withheld from your paychecks, because filing is how you claim a refund.

Form 1040 works together with other forms and schedules. If you have investment income, you'll attach Schedule B. If you're self-employed, you'll attach Schedule C. If you have a mortgage, you'll attach Schedule A to claim itemized deductions. This guide walks you through the main 1040 itself — the core form that ties everything together.

Key Takeaways

  • Form 1040 has two pages: page 1 collects your personal information and income, and page 2 shows tax, credits, and your refund or amount owed.
  • You must enter your Social Security number or ITIN exactly as it appears on your Social Security card, and use the same spelling of your name on every tax document.
  • Income lines include wages from W-2 forms, interest and dividends, capital gains, and self-employment income — each goes on its own line in a specific order.
  • Tax credits like the Earned Income Tax Credit and Child Tax Credit reduce your tax dollar-for-dollar and often produce refunds even when you owe no tax.
  • The form ends with your refund amount or the balance due, and you sign and date it before sending it to the IRS or filing electronically.

Page 1: Personal information and income

The top of page 1 asks for your name, address, and Social Security number (or Individual Taxpayer Identification Number if you don't have a Social Security number). Write your name exactly as it appears on your Social Security card — if your card says "Robert" but you go by "Bob," use "Robert." Mismatched names are a common reason the IRS rejects returns or delays refunds. Your address should be your home on December 31 of the tax year you're filing for, even if you've moved since then.

Below that, you'll select your filing status: Single, Married Filing Jointly, Married Filing Separately, Head of Household, or may have access to Widow(er). Your filing status determines your tax brackets and standard deduction amount. If you're married, filing jointly usually produces a lower tax bill than filing separately, but there are exceptions — for instance, if one spouse has large medical expenses or business losses. If you're unsure, calculate both ways or speak with a tax preparer.

The income section starts with line 1a: wages, salaries, and tips. Copy this number from box 1 of your W-2 form. If you have more than one W-2, add them together. Line 1b asks for any Alaska Permanent Fund dividends — most people leave this blank. Line 2 is interest income from savings accounts and bonds; line 3 is may have access to dividends and capital gains. If you have self-employment income, line 4 is where you enter the net profit from Schedule C. Lines 5 through 9 cover other income types like capital gains, IRA distributions, and rental income. Most people with straightforward jobs leave these blank.

Page 1 continued: Standard deduction and taxable income

After you've entered all your income, you reach the standard deduction. The standard deduction is a fixed dollar amount the IRS lets you subtract from your income before calculating tax. For 2023, the standard deduction was $13,850 for single filers, $27,700 for married filing jointly, and $20,800 for head of household. The IRS raises these amounts each year for inflation. You can find the current year's standard deduction on the IRS website or in the Form 1040 instructions.

If you own a home with a mortgage or have large medical bills, you might benefit from itemizing deductions instead of taking the standard deduction. Itemized deductions go on Schedule A and include mortgage interest, property taxes, charitable donations, and medical expenses above a threshold. Most people take the standard deduction because it's simpler and larger than their itemized total, but you should calculate both to be sure.

Once you've entered your standard deduction (or calculated your itemized deductions on Schedule A), you subtract it from your total income to find your taxable income. This is the number the IRS uses to calculate your federal income tax.

Page 2: Tax, credits, and refund

Page 2 starts with your tax calculation. You'll use the tax tables or tax calculation worksheet in the Form 1040 instructions to find your federal income tax based on your taxable income and filing status. Many people use tax software to do this automatically. Once you have your tax amount, you enter it on line 12.

Next comes the credits section. Tax credits are different from deductions: a deduction reduces your income, but a credit reduces your tax dollar-for-dollar. The Earned Income Tax Credit (EITC) is the largest credit for working people with low to moderate income. If you have children, the Child Tax Credit gives you $2,000 per child under 17. The Child and Dependent Care Credit helps if you paid for daycare so you could work. Other credits include the American Opportunity Credit for education expenses and the Saver's Credit for retirement contributions. You calculate most credits on separate worksheets or schedules, then enter the total on line 24 of Form 1040.

After credits, you calculate your total tax and any additional taxes (like self-employment tax if you're self-employed). Then you enter any federal income tax that was withheld from your paychecks during the year — this comes from box 2 of your W-2 forms. If you made estimated tax payments as a self-employed person, you add those too. The difference between your total tax and your total payments is your refund or the amount you owe.

Common mistakes to avoid

The most frequent error is entering income on the wrong line. Wages go on line 1, not line 4 (self-employment). Interest goes on line 2, not line 3 (dividends). If you put a number on the wrong line, your return may be rejected or your refund delayed. Double-check the source of each income item before you enter it.

A second common mistake is forgetting to sign and date the form. The IRS will not process an unsigned return. If you're married and filing jointly, both spouses must sign. If you're using a tax preparer, they sign as the preparer, but you still sign as the taxpayer.

A third mistake is mismatching your name or Social Security number across forms. If your W-2 says "Jennifer Marie Smith" but you write "Jennifer M. Smith" on your 1040, the IRS computer may not match them. Use the exact spelling and format on every document. The same applies to your Social Security number — if you transpose a digit, the IRS won't connect your income to your return.

Finally, many people forget to attach required schedules. If you have self-employment income, you must attach Schedule C. If you itemize deductions, you must attach Schedule A. If you have capital gains or losses, you must attach Schedule D. The Form 1040 instructions list which schedules you need based on your situation.

Filing your completed form

Once you've filled out Form 1040 and any required schedules, you have two options: file electronically or mail a paper copy. Electronic filing is faster, more accurate, and produces a refund in 21 days or less if you choose direct deposit. Most tax software handles electronic filing for you. If you mail a paper return, use the address listed in the Form 1040 instructions for your state — do not send it to a local IRS office. Paper returns take 4 to 6 weeks to process.

Keep a copy of your completed return and all supporting documents (W-2s, 1099s, receipts, bank statements) for at least three years. The IRS can audit returns from the past three years, and you'll need these documents to prove your numbers if they ask.

Frequently Asked Questions

Do I have to file Form 1040 if I had taxes withheld but earned less than the filing threshold?

No, you're not required to file, but you should. If you had federal income tax withheld from your paychecks and you earned less than the threshold, you likely overpaid and are owed a refund. Filing is the only way to claim it. The IRS does not automatically refund overpaid tax.

What's the difference between a W-2 and a 1099, and where do they go on Form 1040?

A W-2 is issued by an employer and reports wages you earned as an employee. A 1099 is issued by a client or business and reports income you earned as an independent contractor or from investments. W-2 wages go on line 1 of Form 1040. Self-employment income from a 1099-NEC goes on Schedule C, and the net profit from Schedule C goes on line 4 of Form 1040. Interest and dividend 1099s go on lines 2 and 3.

Can I file Form 1040 if I'm married but my spouse doesn't want to file?

You can file as Married Filing Separately, but this usually results in a higher tax bill and disqualifies you from many credits. If your spouse has no income and no tax liability, they don't have to file, but you can still file as Married Filing Jointly if you have their Social Security number and permission. Consult a tax preparer if your situation is complex.

What happens if I make a mistake on Form 1040 after I file it?

If you discover an error after filing, you can file an amended return using Form 1040-X. You must file the amended return within three years of the original filing date to claim a refund, or within two years of paying the tax, whichever is later. The IRS will also contact you if they find an error during processing.

Do I need to file Form 1040 if I'm a dependent on my parents' return?

It depends on your income. If you're claimed as a dependent and your earned income exceeds the standard deduction for a dependent (which is lower than for an independent person), you must file. For 2023, a dependent with only wages must file if they earned more than $13,850, but the threshold is lower if they also have unearned income like interest. Check the Form 1040 instructions for the exact threshold for your situation.