US Individual Income Tax Return

Who Files Form 1040

Every US citizen, resident alien, and (in some cases) nonresident alien who meets the IRS filing thresholds for the tax year. Variants include 1040-SR for taxpayers age 65+ and 1040-NR for nonresident aliens.

What Form 1040 Reports

Form 1040 is the master individual return and is supplemented by schedules: Schedule A (itemized deductions), Schedule B (interest and dividends), Schedule C (self-employment), Schedule D (capital gains), Schedule E (rentals and pass-through K-1 income), Schedule SE (self-employment tax), and others. The return calculates total income, AGI, taxable income, tax liability, refundable and nonrefundable credits, and the resulting refund or balance due.

Key Deadlines

• April 15: annual filing deadline (or next business day if it falls on a weekend or holiday)
• Six-month automatic extension available via Form 4868 (extension of time to file, not to pay)
• October 15: extended deadline for filers who submitted Form 4868

Common Mistakes

• Forgetting to report 1099 income because no form was issued (you still owe tax)
• Missing the home office deduction or vehicle deduction for self-employed work
• Filing the wrong status: head of household vs single is a frequent IRS audit trigger
• Skipping estimated tax payments and incurring underpayment penalties

Best Practices

• Reconcile your prior-year refund or balance against the current return so any old underpayment penalty does not surprise you.
• Run the standard deduction versus itemized calculation both ways, especially after a SALT cap change, a paid-off mortgage, or a high-medical-expense year.
• Save digital copies of every W-2, 1099, K-1, and 1099-B before you file. CP2000 responses are dramatically easier when source documents are already in one folder.
• Compare adjusted withholding plus estimates against safe-harbor (100 percent of last year tax, or 110 percent if AGI exceeded 150K) to avoid Section 6654 penalties.
• Always file electronically with direct deposit. Paper returns add 6 to 8 weeks to refund timing and increase mismatch errors.

Source: Official Form 1040 information at IRS.gov