What the IRS Form 1040 Is and Why You File It

The 1040 is the main form you use to report your yearly income to the IRS

The Form 1040 is the federal income tax return form that most U.S. taxpayers file each year. It tells the Internal Revenue Service (IRS) how much money you earned, what deductions and credits you can claim, and how much tax you owe or should receive back. The IRS uses this form to calculate whether you paid enough tax throughout the year through paycheck withholding or estimated payments.

You file a 1040 if you are a U.S. citizen or resident alien with income from wages, self-employment, investments, or other sources. The form itself is relatively short — usually two pages — but it connects to schedules and worksheets that provide details about specific types of income or deductions depending on your situation.

Filing a 1040 is required by law if your income exceeds a certain threshold. That threshold changes each year and depends on your age, filing status, and type of income. The IRS publishes the current thresholds on its website each January.

Key Takeaways

• The 1040 is the standard form for reporting federal income tax, and most taxpayers file one each year by April 15 or the next business day.
• The form asks for your income from all sources, deductions, tax credits, and personal information, then calculates your total tax liability.
• You must file a 1040 if your income is above the annual threshold set by the IRS, which varies by age and filing status.
• The 1040 connects to additional schedules — such as Schedule C for self-employment or Schedule A for itemized deductions — depending on what income or deductions you have.
• You can file by mail, through IRS Free File if your income is below a certain level, or by paying a tax software company or tax preparer.

What information the 1040 asks for

The 1040 begins with your personal details: name, address, Social Security number, and filing status (single, married filing jointly, married filing separately, head of household, or may have access to widow or widower). You also indicate whether anyone can claim you as a dependent.

The form then has sections for income. You report wages from a W-2 job, interest and dividends, capital gains or losses, self-employment income, rental income, and other sources. Most of this information comes from documents your employer, bank, or investment company sends you — a W-2 for wages, a 1099-INT for interest, a 1099-DIV for dividends, and so on.

Next comes deductions. You choose either the standard deduction (a flat amount set by the IRS each year) or itemized deductions (specific expenses you add up yourself, reported on Schedule A). Most taxpayers use the standard deduction because it is simpler and often larger.

The form also asks about tax credits — direct reductions in the tax you owe, such as the Earned Income Tax Credit or the Child Tax Credit. Credits are more valuable than deductions because they reduce your tax dollar-for-dollar rather than reducing your taxable income.

How the 1040 calculates what you owe

The 1040 works through a series of steps. First, it adds up all your income from every source. Then it subtracts either your standard deduction or your itemized deductions to arrive at your taxable income. The IRS tax tables or tax rate schedules then tell you how much federal income tax you owe on that amount.

Next, the form accounts for any tax credits you are may have access to to. These reduce your tax liability directly. If you paid tax throughout the year via paycheck withholding or estimated tax payments, the form subtracts those payments from what you owe. If you paid more than you owe, you receive a refund. If you paid less, you owe the difference.

The final line of the 1040 shows either your refund or the amount you must pay by the filing important date, which is usually April 15.

The difference between the 1040 and other tax forms

The IRS offers a shorter form called the 1040-SR for taxpayers age 65 and older. It has the same purpose as the regular 1040 but uses larger print and slightly reorganized sections to make it easier to read. You can use either form if you are 65 or older.

The 1040-NR is for nonresident aliens — people who are not U.S. citizens and do not have a green card. It follows different rules for what income is taxable and what deductions are allowed.

Before 2018, the IRS offered forms called the 1040-A and 1040-EZ for simpler tax situations. Those forms no longer exist. Now, all taxpayers use the 1040, though the complexity of what you attach to it varies widely.

Schedules and attachments that go with the 1040

Depending on your income and situation, you attach additional forms to your 1040. Schedule C is for self-employment income and expenses. Schedule A lists itemized deductions such as mortgage interest, state and local taxes, and charitable donations. Schedule D reports capital gains and losses from the sale of stocks, real estate, or other investments.

Other schedules cover rental income (Schedule E), farm income (Schedule F), and income from partnerships or S corporations (Schedule K-1, which you receive from the business). If you have a child and claim the Child Tax Credit, you may need to fill out additional worksheets to calculate the credit correctly.

The IRS website lists which schedules you need based on your situation. Tax software typically guides you through questions and automatically includes the right schedules.

How to file your 1040

You have three main options: file by mail, file electronically through tax software, or hire a tax preparer or CPA to file for you.

If you file by mail, you print the form, fill it out by hand or using tax software, and mail it to the IRS address listed in the instructions. The IRS processes paper returns more slowly than electronic ones, and refunds take longer to arrive.

Electronic filing is faster. The IRS offers IRS Free File, a program that lets you file for free if your income is below a certain threshold (the limit changes each year). You choose from a list of IRS-approved software companies that offer free versions of their products to those who meet the income limit. If your income is above the limit, you can buy tax software from companies like TurboTax, H&R Block, or TaxAct, or you can use a tax preparer.

Tax preparers and CPAs charge a fee but handle the entire process for you. They may catch deductions or credits you missed and can represent you if the IRS has questions about your return.

important date and penalties for not filing

The important date to file your 1040 is usually April 15 of the year following the tax year. If April 15 falls on a weekend or holiday, the important date moves to the next business day. You can request an automatic extension that gives you until October 15, but an extension to file is not an extension to pay. If you owe tax, you must pay by April 15 or face interest and penalties, even if you file the extension.

If you do not file a 1040 when you are required to, the IRS can assess a failure-to-file penalty. If you owe tax and do not pay it by the important date, you face a failure-to-pay penalty plus interest on the unpaid amount. The longer the debt sits unpaid, the more interest accrues.

If you are owed a refund, there is no penalty for filing late, but you must file within three years to claim it. After three years, the IRS keeps the refund.

Frequently Asked Questions

Do I have to file a 1040 if I did not earn much money?

It depends on how much you earned and your filing status. The IRS sets an annual income threshold — for example, in 2023, a single person under 65 had to file if they earned more than $13,850. If you earned less, you are not required to file. However, if you had tax withheld from your paychecks, filing may get you a refund even though you were not required to file.

What is the difference between a refund and a tax credit?

A tax credit reduces the amount of tax you owe. A refund is money the IRS sends you because you paid more tax than you owed. Some credits are refundable, meaning if the credit is larger than your tax liability, the IRS sends you the difference as a refund. Others are nonrefundable and can only reduce your tax to zero.

Can I file a 1040 on paper, or do I have to file electronically?

You can file on paper by mail. However, the IRS processes electronic returns faster, and you receive refunds more quickly. If you use tax software, it usually costs less to file electronically than to print and mail.

What happens if I make a mistake on my 1040?

If you discover an error after you file, you can file an amended return using Form 1040-X. You have three years from the original filing date to file an amendment. If the IRS finds an error, they will contact you and explain the issue.

Do I need to keep my 1040 after I file it?

Yes. Keep a copy of your filed 1040 and all supporting documents (W-2s, 1099s, receipts for deductions) for at least three years. The IRS can audit returns up to three years old, and longer in some cases. Having your records makes it easier to respond if the IRS has questions.