What you need before you start filing
Before you open a tax form or software, gather the documents that show your income, deductions, and credits for the year. The IRS calls these your source documents. You will need them whether you file on paper or electronically.
For wages and salary, you need your W-2 forms from each employer — one copy for each job you held during the year. Your employer must send these to you by January 31. For self-employment income, gather receipts and records showing what you earned and what you spent. For investment income, you need 1099 forms: a 1099-INT for interest, 1099-DIV for dividends, 1099-B for stock sales, and others depending on your income type. If you received unemployment benefits, you will have a 1099-G. If you made estimated tax payments during the year, write down the dates and amounts.
If you are claiming deductions, collect receipts for mortgage interest (Form 1098), property taxes, charitable donations, and medical expenses. If you have dependents, write down their full names and Social Security numbers. If you are claiming education credits, gather documents from your school showing tuition paid. Have your prior year tax return available — it contains information you may need to reference.
Key Takeaways
- Gather all W-2 forms, 1099 forms, and receipts for deductions before you begin, because the IRS matches your return against documents your employers and financial institutions send them.
- You can file by paper using the official 1040 form and schedules, or electronically using tax software or a tax professional, and the IRS processes electronic returns faster.
- The 1040 itself is short — it asks for your name, address, filing status, and income totals — but you attach schedules that break down specific types of income and deductions.
- You must sign and date your return, and if you are married filing jointly, both spouses must sign; unsigned returns are rejected and not processed.
- The important date to file is usually April 15, but if that date falls on a weekend or holiday, the important date moves to the next business day.
Choosing between paper filing and electronic filing
You have two paths: file a paper 1040 by mail, or file electronically. Electronic filing is faster — the IRS typically processes e-filed returns within 21 days, while paper returns take six to eight weeks. The IRS also confirms receipt of an electronic return within 24 hours, so you know it arrived. Paper filing is an option if you prefer to work on paper or have a very straightforward return with no schedules.
If you file electronically, you can use free IRS-approved tax software, hire a tax professional (a CPA, enrolled agent, or tax preparer), or use a commercial tax software product that you pay for. The IRS Free File program offers free software to people whose income is below a certain threshold — check IRS.gov to see if you may have access to. If you use paid software or a professional, you will enter your information into their system, and they will file the 1040 and all schedules electronically on your behalf.
If you file on paper, you will print the 1040 form and any schedules you need, fill them out by hand or on your computer, sign and date them, and mail them to the IRS address listed in the form instructions. The address depends on your state and whether you are including a payment.
How to fill out the 1040 itself
The 1040 form has two pages. The first page asks for your personal information: your name, address, and Social Security number in the top section. You then 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 rate and which deductions you can claim. If you are unsure which status applies to you, the IRS website has a tool to help you decide.
Below that, you enter your income. Line 1 asks for wages, salaries, and tips — this is the total from all your W-2 forms, box 1. Line 2 asks for interest income, line 3 for dividends, and so on for each type of income you received. If you have self-employment income, you will fill out Schedule C first, then enter the net profit from that schedule on line 4 of the 1040. If you have capital gains or losses, you fill out Schedule D and enter the result on line 7.
You add up all your income sources and enter the total on line 9. Then you choose whether to take the standard deduction or itemize deductions. The standard deduction is a fixed amount that depends on your filing status and age — for 2024, it ranges from $14,600 for a single filer under 65 to $29,200 for a married couple filing jointly both age 65 or older. If your itemized deductions (mortgage interest, property taxes, charitable gifts, medical expenses) add up to more than the standard deduction, you itemize by filling out Schedule A. Otherwise, you take the standard deduction.
You subtract your deduction from your income to get your taxable income, then look up your tax in the tax tables provided with the form. If you have credits — the child tax credit, education credits, or others — you subtract those from your tax to get your final tax owed. If you had taxes withheld from your paychecks or made estimated payments, you subtract those too. The result is either a refund (if you overpaid) or a balance due (if you underpaid).
Attaching schedules and supporting forms
The 1040 is the main form, but most people need to attach additional schedules that break down specific income or deductions. You do not file these separately — you staple them to the back of your 1040 in the order the IRS specifies. If you file electronically, the software attaches them automatically.
Schedule A is for itemized deductions — mortgage interest, property taxes, state and local taxes, charitable donations, and medical expenses. You only file this if you itemize instead of taking the standard deduction. Schedule B is for interest and dividend income over certain thresholds. Schedule C is for self-employment income and expenses — you fill this out if you are a sole proprietor or freelancer. Schedule D is for capital gains and losses from selling stocks, real estate, or other investments. Schedule 1 is for other income sources like alimony, rental income, or prizes. The form instructions tell you which schedules you need based on your situation.
You also attach Form 8863 if you are claiming education credits, Form 2441 if you are claiming the child and dependent care credit, or Form 3468 if you are claiming energy credits. The instructions that come with the 1040 list every schedule and form you might need and tell you exactly when to use each one.
Signing, dating, and submitting your return
Your return is not valid unless you sign and date it. If you are married filing jointly, both spouses must sign. If you are filing on paper, you sign in blue or black ink on the signature line on page 2 of the 1040. If you are filing electronically, you sign using a PIN or an electronic signature method that your software or tax professional provides.
If you owe taxes, you can pay when you file using a credit card, debit card, or electronic bank transfer. The IRS also accepts payment plans if you cannot pay the full amount at once. If you are due a refund, you choose how to receive it — by direct deposit to your bank account (which is faster) or by check mailed to your address.
If you are filing on paper, mail your return to the address shown in the 1040 instructions. That address varies by state and by whether you are including a payment. Use certified mail if you want proof of delivery. If you are filing electronically, your software or tax professional submits it directly to the IRS, and you receive a confirmation number.
What happens after you file
If you file electronically, the IRS sends you an acknowledgment within 24 hours confirming they received your return. They then process it and send you a notice of assessment within 21 days if everything is correct. If you are due a refund, it is deposited into your bank account or mailed as a check. If you owe taxes and did not pay when you filed, the IRS sends you a bill with payment instructions.
If you file on paper, the IRS sends you a notice of assessment by mail after they process your return, which takes six to eight weeks. If there are errors or missing information, they send you a letter asking for clarification or corrections. Keep a copy of your filed return and all supporting documents for at least three years in case the IRS asks questions.
Common mistakes to avoid
The most common error is entering the wrong Social Security number — yours, your spouse's, or your dependents'. Double-check these before you submit. Another frequent mistake is forgetting to sign the return; unsigned returns are rejected and must be resubmitted. If you are married filing jointly, make sure both spouses sign.
Many people also forget to attach required schedules or forms. If your income includes self-employment earnings, you must attach Schedule C. If you are itemizing deductions, you must attach Schedule A. If you have capital gains, you must attach Schedule D. The form instructions list every schedule you need based on your income type.
A third common error is mismatching the income on your 1040 with the income reported on your W-2 or 1099 forms. The IRS receives copies of these forms from your employers and financial institutions, and they check that the numbers match. If they do not, the IRS sends you a letter asking for an explanation.
Frequently Asked Questions
Can I file my 1040 before I receive all my W-2 and 1099 forms?
No. You need all your income documents before you file because the IRS matches your return against the copies your employers and financial institutions send them. If you file before receiving a 1099, the IRS will contact you when the form arrives and the income does not match your return. It is safer to wait until you have every document.
What if I make a mistake after I file?
If you discover an error after filing, you file an amended return using Form 1040-X. You must file the amended return within three years of the original filing date. If the error results in a refund, the IRS processes it within 16 weeks of receiving your amended return.
Do I need to file a 1040 if my income is very low?
It depends on your filing status and income level. The IRS publishes income thresholds each year below which you do not have to file. However, if you had taxes withheld from your paychecks, you should file anyway to get a refund of the money withheld.
Can I file my 1040 on my phone?
Most tax software has a mobile app that lets you enter information on your phone, but you still need to review and sign the return before it is submitted. Some people use their phone to gather documents and take photos of receipts, then complete the filing on a computer.
What if I cannot file by April 15?
You can request an extension by filing Form 4868 before the important date. An extension gives you until October 15 to file your return. However, an extension to file is not an extension to pay — if you owe taxes, you should pay by April 15 to avoid penalties and interest, even if you have not filed yet.