Tax Filing Checklist for 2027: Documents, Deadlines and Mistakes to Avoid

Tax season for the 2026 tax year opens in late January 2027, and the filing deadline for most people is Thursday, April 15, 2027. Gathering your paperwork early makes filing faster and helps you catch missing forms before the IRS does.

Income documents

• Form W-2 from each employer (due to you by February 1, 2027).
• Form 1099-NEC or 1099-K for freelance, gig or platform income. Report all self-employment income, even without a form, and use the self-employment tax calculator to estimate what you owe.
• Form 1099-INT and 1099-DIV for bank interest and dividends.
• Form 1099-B for stock, fund and crypto sales. Check the cost basis and the holding period; the capital gains tax calculator shows how short- and long-term gains are taxed.
• Form 1099-R for retirement account distributions and SSA-1099 for Social Security.
• Form 1099-G for unemployment benefits or state tax refunds.

Deductions and credits

• Form 1098 for mortgage interest, plus property tax bills, if you might itemize. Most people take the standard deduction: $16,100 for single filers and $32,200 for married couples filing jointly in 2026.
• Form 1098-E for student loan interest (up to $2,500 deductible).
• Form 1098-T for tuition, used for education credits.
• Records of IRA and HSA contributions. You can contribute to an IRA for 2026 until the April 15, 2027 deadline.
• Childcare provider names, tax IDs and amounts paid, for the child and dependent care credit.
• Charitable donation receipts if you itemize.

Key dates

An extension gives more time to file, not to pay. Pay what you expect to owe by April 15 to avoid interest and penalties.

Common mistakes that delay refunds

• Typos in Social Security numbers or bank routing numbers.
• Missing a 1099. The IRS gets a copy and will send a notice.
• Choosing the wrong filing status; head of household gives a larger standard deduction than single if you qualify.
• Forgetting to sign, or to include both spouses’ signatures on a paper joint return.
• Claiming credits without the required forms, such as the Earned Income Tax Credit, which can hold refunds until mid-February.

Estimate before you file

Run your numbers through the income tax calculator to see whether to expect a refund or a balance due, and adjust your W-4 for next year using the paycheck calculator. For brackets and examples, see 2026 tax brackets explained.