Common Tax Filing Mistakes in 2026 and How to Avoid Them
Tax filing errors are more common than most people realize. Even experienced filers make mistakes that lead to delayed refunds, IRS notices, or missed savings. For the 2026 filing season, covering the 2025 tax year, certain mistakes are particularly prevalent given recent changes to reporting requirements, new deductions, and evolving rules around digital income. This guide covers the most common errors and what you can do to avoid them.[1][2]
1. Incorrect Personal Information
Entering the wrong Social Security number, misspelling a name, or using an old address are among the most frequent errors on tax returns. These mistakes can cause the IRS to reject your return entirely or delay processing. Always double-check that the names, Social Security numbers, and dates of birth for yourself, your spouse, and any dependents match what appears on Social Security cards.[1]
2. Choosing the Wrong Filing Status
Selecting the wrong filing status is a common mistake with significant tax consequences. Head of household status, for example, provides a larger standard deduction than single status, but it has specific requirements that many filers misunderstand. Similarly, married couples sometimes file separately without realizing that joint filing often produces a lower combined tax liability.[2][3]
Use the IRS interactive filing status tool at IRS.gov if you are uncertain which status applies to your situation.
3. Missing Income
All income must be reported, whether or not you received a formal tax document for it. Commonly overlooked income sources include:[1][2]
Freelance payments under $600 from a single client, which are still taxable even though no 1099-NEC is required
Income from payment apps such as Venmo, Cash App, or PayPal
Bartering income, gambling winnings, and prizes
Rental income from short-term rentals
Cryptocurrency transactions, including trades, staking rewards, and NFT sales
In 2026, the IRS has increased scrutiny of payment platform income following new 1099-K reporting thresholds that went into effect in recent years. Failing to report income that shows up on a 1099-K that the IRS also receives is a reliable way to receive a notice.[3]
4. Math Errors
Manual calculation errors are one of the most easily preventable mistakes. Simple addition or subtraction mistakes can lead to an incorrect refund, an unexpected bill, or a notice from the IRS asking for clarification. Using tax software largely eliminates this risk because the software handles all calculations automatically. If you are filing on paper, consider using a calculator and reviewing each entry twice.[1]
5. Forgetting to Sign and Date
An unsigned tax return is not a valid return. If you file on paper, both spouses must sign a joint return. Electronic returns require you to enter a self-select PIN or your prior year adjusted gross income as a digital signature. Forgetting this step delays processing and may result in your return being rejected.[2]
6. Missing or Incorrect Bank Information
If you are expecting a refund and choose direct deposit, incorrect account or routing numbers will cause your refund to be delayed or sent to the wrong account. Verify your bank information carefully before submitting. If a deposit goes to the wrong account, recovering the funds can be a lengthy process.[1][3]
7. Not Claiming Eligible Credits and Deductions
Many taxpayers miss deductions and credits they are legitimately entitled to. Common overlooked items include:[1][2]
Earned Income Tax Credit, which is overlooked by millions of qualifying filers each year
Child and Dependent Care Credit for working parents
American Opportunity Credit or Lifetime Learning Credit for education expenses
Student loan interest deduction of up to $2,500
Deduction for contributions to a traditional IRA
Saver's Credit for lower-income taxpayers who contributed to retirement accounts
Energy-efficient home improvement credits
8. Overlooking Deductions for Self-Employed Filers
Freelancers and self-employed individuals frequently miss deductible business expenses. Health insurance premiums paid out of pocket, the self-employment tax deduction, qualified business income deduction, home office expenses, and business vehicle mileage are all commonly overlooked. Each missed deduction increases your taxable income unnecessarily.[3]
9. Filing Late Without an Extension
Failing to file by the April 15, 2026 deadline without requesting an extension triggers a failure-to-file penalty of 5 percent of unpaid taxes per month, up to 25 percent. If you cannot complete your return in time, file Form 4868 by the deadline to get an automatic six-month extension. Remember that the extension applies to filing, not to payment, so estimate your tax owed and pay by April 15 to minimize penalties.[1][2]
10. Not Reporting Cryptocurrency Transactions
The IRS treats cryptocurrency as property, and every taxable event, including selling, trading, or using crypto to purchase goods or services, must be reported on your return. Receiving crypto through staking or mining is also taxable. The IRS has made crypto reporting a focus area in recent years, and blockchain transaction records make it easier for the IRS to detect unreported activity.[2][3]
11. Forgetting to Include All W-2s and 1099s
If you held multiple jobs, had multiple investment accounts, or received income from several sources in 2025, it is easy to overlook one or more income forms. Create a checklist of every income source before you start filing, and verify that you have received and included a form from each one.[1]
12. Not Keeping Records After Filing
Tax records do not become irrelevant once your return is filed. The IRS can audit returns filed within the last three years in most circumstances and up to six years if it suspects substantial underreporting of income. Keep copies of your return, all supporting documents, and any IRS correspondence for at least three years, and ideally seven years for returns involving unusual items.[2]
Conclusion
Most tax filing mistakes are preventable with careful preparation, thorough document collection, and careful review before submitting. Using reliable tax software reduces calculation errors and helps identify deductions you might otherwise miss. If your financial situation is complex, working with a qualified tax professional adds an additional layer of review that can catch errors before the IRS does.[1][2][3]
Sources
[1] IRS, Common Errors on Tax Returns, IRS.gov/newsroom
[2] IRS, Tax Time Guide, IRS.gov/newsroom/tax-time-guide
[3] CNBC, Most Common Tax Mistakes, cnbc.com
