Tax Filing and Compliance — United States
The US operates a self-assessment tax system where individuals are responsible for filing annual tax returns. Employers withhold estimated taxes from paychecks, and annual returns reconcile withholding with actual tax liability. Electronic filing is standard and covers federal and state returns.
Tax Filing and Compliance
The US operates a self-assessment tax system where individuals are responsible for filing annual tax returns. Employers withhold estimated taxes from paychecks, and annual returns reconcile withholding with actual tax liability. Electronic filing is standard and covers federal and state returns.
Who Must File
Must file if gross income meets or exceeds the standard deduction amount. Even if below threshold, file to claim refundable credits (EITC, CTC) or recover withheld taxes.
Self-employed individuals must file if net self-employment income is $400 or more. Must pay self-employment tax (Social Security + Medicare) in addition to income tax.
Self-employed, freelancers, and those with significant non-wage income must make quarterly estimated payments (Form 1040-ES). Due April 15, June 15, September 15, January 15.
US citizens and Green Card holders must file regardless of where they live or earn income. Automatic 2-month extension for those living abroad (to June 15).
Filing Deadlines 2027 (for 2026 tax year)
Form 1040 due by April 15. Taxes owed must be paid by this date even if requesting an extension. Late filing penalty: 5% per month, up to 25%.
File Form 4868 for automatic 6-month extension to file (not to pay). Any estimated tax owed must still be paid by April 15 to avoid penalties and interest.
Most states follow the April 15 federal deadline. Some states (e.g., Hawaii, Delaware) have different dates. Extension rules also vary by state.
FinCEN 114 due April 15 with automatic extension to October 15. Required if aggregate value of foreign financial accounts exceeds $10,000 at any point during the year.
Key Tax Forms
Annual wage and tax statement from each employer. Shows gross wages, federal/state tax withheld, Social Security and Medicare taxes. Due to employees by January 31.
1099-NEC (freelance income), 1099-INT (interest), 1099-DIV (dividends), 1099-B (brokerage sales), 1099-DA (crypto). Due by January 31 or February 15.
Main individual tax return filed with IRS. Includes schedules for self-employment (C), capital gains (D), rental income (E), and itemized deductions (A).
Reports income and expenses from sole proprietorship or freelancing. Net profit flows to Form 1040 and is subject to both income tax and self-employment tax.
After Filing
Refunds processed within 21 days for e-filed returns. Direct deposit fastest. Paper returns take 6-8 weeks. Track status at irs.gov/refunds or IRS2Go app.
If you owe: pay via IRS Direct Pay (bank account), credit/debit card, check, or installment agreement (Form 9465). Penalties and interest accrue on unpaid balances.
IRS audits less than 1% of returns. Higher audit rates for high income ($1M+), self-employed, and returns with large deductions. Keep records for at least 3 years.
If you discover an error after filing, file Form 1040-X within 3 years of original filing date. Can claim missed deductions or credits retroactively.
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Social Security & Medicare (FICA)
The US social insurance system is funded through FICA (Federal Insurance Contributions Act) taxes, covering Social Security (retirement, disability, survivors) and Medicare (healthcare for 65+). Contributions are mandatory for all W-2 employees and self-employed individuals. The system is funded jointly by employees and employers.
02Tax Deductions and Credits
The US tax system offers two paths for deductions: the standard deduction or itemized deductions. Tax credits directly reduce tax owed and are generally more valuable than deductions. The OBBBA (2025) made permanent most deduction provisions from the 2017 Tax Cuts and Jobs Act.
03How Your Tax is Calculated
US federal income tax is calculated progressively using marginal rates. Tax is withheld from paychecks throughout the year and reconciled when you file your annual return. State income taxes (where applicable) are calculated separately.
04Capital Income & Investment Taxation
The US taxes capital gains and investment income separately from ordinary income, with preferential rates for long-term holdings. The 3.8% Net Investment Income Tax (NIIT) applies to high earners. The US has a federal estate tax but no wealth tax.
05Special Features of the US Tax System
The US tax system has unique features that distinguish it from most other countries: citizenship-based taxation, a complex federal-state-local structure, extensive retirement savings incentives, and no national VAT or sales tax.