How to file your income tax return in United States
Who must file an income tax return in United States, the tax year and deadline, what documents you need, how to file with Internal Revenue Service (IRS) and state departments of revenue, and what happens if you are late.
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Updated for 2026
Last reviewed September 2026
Who must file
In most countries, anyone with income above the tax-free amount who was not fully taxed through payroll withholding must file: the self-employed, landlords, company directors and anyone with more than one income source. Companies file their own return. Check Internal Revenue Service (IRS) and state departments of revenue's rules for employees, who are sometimes exempt or auto-assessed.
Most people with income above the standard deduction file Form 1040; self-employed people file Schedule C and pay self-employment tax once net earnings exceed $400.
Tax year and deadline
Every country fixes a tax year and a filing deadline a few months after it ends. Internal Revenue Service (IRS) and state departments of revenue publishes both. Put the deadline in your calendar with a reminder a month before, because late filing is penalised even when no tax is due.
Tax year: 1 January to 31 December.
Tax year is the calendar year; returns are due 15 April, extendable to 15 October (payment is still due in April). Estimated tax is paid quarterly.
What you need
Your EIN and login for Internal Revenue Service (IRS) and state departments of revenue's online service.
Employment income statements from each employer showing pay and tax withheld.
Your invoices, bank statements and expense records if you are self-employed.
Certificates for pension contributions, insurance, donations and other reliefs you will claim.
Last year's return, to check nothing is missed.
Filing step by step
Gather W-2s, 1099s, and business income and expense records.
File electronically with IRS Free File or tax software, or with a preparer.
Self-employed: complete Schedule C and Schedule SE.
Pay by 15 April or set up an IRS payment plan.
Employees and salary tax
Employers in United States withhold income tax from salaries under the 2025 federal, single filer bands and pay it to Internal Revenue Service (IRS) and state departments of revenue. The United States salary tax calculator shows the tax and take-home for any gross salary, which is a quick way to check your payslip before you file.
If you are late
Late returns attract a fixed penalty and late payment attracts interest, both set by Internal Revenue Service (IRS) and state departments of revenue. File even if you cannot pay in full; penalties for not filing are usually heavier than for paying late, and most authorities allow instalment plans.
Questions people ask
Do I need to file if my employer already deducted tax?
It depends on United States's rules. Some countries require every taxpayer to file, some auto-assess employees, others exempt employees with a single employer and no other income. The rule for United States is set out above.
What if I had no income?
If you are registered with Internal Revenue Service (IRS) and state departments of revenue, you may still have to file a nil return. Failing to do so is treated as a late return in many countries.
Can I file late without a penalty?
Rarely. Some authorities allow an extension if requested before the deadline. Otherwise file as soon as possible; penalties often grow with time.
Should I use an accountant?
If you are employed with no other income, the online service is designed for you. If you run a business or have foreign income or property, an accountant usually saves more than the fee.
Written from published tax-authority guidance and reviewed on 2026-09-03. Everything here is indicative rather than a ruling on your circumstances, and rules change. Confirm anything you rely on with Internal Revenue Service (IRS) and state departments of revenue before acting on it, and tell us if you find something out of date so we can correct it.
This guide explains the rules in general terms and is not tax advice for your circumstances. Confirm your position with a qualified adviser or with Internal Revenue Service (IRS) and state departments of revenue.
🇺🇸 United States
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Invoices, quotations, purchase orders, credit notes and waybills in USD, with Sales tax and the EIN on the document. Plus a Sales tax calculator and a salary tax calculator. Everything runs in your browser and nothing is uploaded.