The Most Common Income Tax Return Errors and How You Can Avoid Them When Filing Your Return
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The Most Common Income Tax Return Errors and How You Can Avoid Them When Filing Your Return

Many income tax return errors are caused by carelessness or failing to double check the information you enter, even with electronic filing

August 10, 2025

The 2026 tax filing season will cover your 2025 income, and the Internal Revenue Service (IRS) expects most taxpayers will file electronically. In fact, in recent years, more than 90% of all individual returns have been e-filed, whether self-prepared or completed by a tax professional. The due date for most taxpayers is April 15, 2026. Residents of Maine and Massachusetts have until April 17, 2026, due to the observance of Patriots’ Day and Emancipation Day. While modern filing systems and software catch many mistakes, a surprising number of tax returns still have errors that can delay refunds, increase the risk of audits, or cause penalties.

Key 2026 Tax Season Changes

  • Standard deduction increases – For the 2025 tax year, the standard deduction is $15,050 for single filers and married individuals filing separately, $30,100 for married couples filing jointly, and $22,550 for heads of household.
  • Retirement contribution limits – The 401(k) employee contribution limit rises to $23,500, with a $7,500 catch-up limit for those aged 50 and older. The IRA contribution limit increases to $7,500, with a $1,000 catch-up.
  • Earned Income Tax Credit (EITC) – Maximum credit for taxpayers with three or more children rises to $8,150. Income limits adjust based on filing status and number of dependents.
  • Child Tax Credit – The maximum remains $2,000 per qualifying child under age 17, with $1,700 refundable, subject to income limits.
  • Health Savings Account (HSA) limits – Contribution limits increase to $4,300 for individuals and $8,550 for family coverage, with a $1,000 catch-up for those aged 55 and older.
  • IRS enforcement updates – The IRS continues expanded use of digital notices and correspondence, so keeping your mailing address, phone number, and email current with the IRS is important.

Missing the filing deadline

Missing the deadline can cost you. If you owe taxes and file late without an approved extension, the IRS imposes a failure-to-file penalty of 5% of the unpaid taxes for each month or part of a month the return is late, up to 25%. The failure-to-pay penalty is generally 0.5% per month. Interest also accrues daily on unpaid balances. Even if you cannot pay in full, file on time and arrange a payment plan to avoid the largest penalties.

Entering incorrect Social Security numbers or personal information

Incorrect Social Security numbers (SSNs) are among the most common mistakes. Every name and SSN on your return must match exactly what is on the Social Security card. This applies to spouses and dependents. An incorrect SSN can result in denial of valuable credits like the Child Tax Credit or Earned Income Tax Credit, and can delay your refund significantly. Always double check this information before submitting your return.

Illegible or smudged information

Paper filers should ensure all printed text is clear and dark enough to read. Smudged or faint ink can cause data entry errors. Even though most people e-file, paper returns are still used by some taxpayers, and legibility is critical. If handwriting is poor, consider typing the forms or filing electronically to avoid misinterpretation by IRS staff.

Selecting multiple filing statuses

You can only choose one filing status for a given tax year. While tax software prevents multiple selections, paper filers sometimes mistakenly check more than one box. The IRS will reject or delay processing until the correct status is confirmed. Common statuses are Single, Married Filing Jointly, Married Filing Separately, Head of Household, and Qualifying Widow(er) with Dependent Child. Review the eligibility rules before filing.

Spelling errors in names

Spelling mistakes, especially in a dependent’s name, can cause rejections. The spelling on the return must exactly match the Social Security Administration records. Even minor differences, such as using a nickname, can lead to processing delays or lost tax benefits.

Math mistakes

Math errors continue to occur, particularly on paper returns. These can lead to underpayment notices or refund adjustments. Using reputable tax software or a professional preparer greatly reduces this risk, as calculations are automated. However, always review key figures, including totals for income, deductions, and credits.

Mailing to the wrong IRS address

IRS mailing addresses change occasionally. If you file by paper, always use the current address listed in the instructions for your specific form and state of residence. Mailing to an old address can delay your return by weeks. E-filing eliminates this problem entirely.

Incorrect bank account information

Routing and account numbers must be entered exactly if you want direct deposit of your refund. Even a single wrong digit can send your refund to the wrong account or cause it to be returned to the IRS. For 2026, the IRS continues to allow taxpayers to split refunds into up to three accounts, but you should verify each number before submission.

Not requesting an extension when needed

If you cannot file by April 15, 2026 (or April 17, 2026, in ME and MA), file for an extension using Form 4868 or IRS Free File. An extension gives you until October 15, 2026, to file, but it does not extend the deadline to pay taxes owed. Pay as much as possible by the April due date to minimize penalties and interest.

Missing required forms or schedules

Paper filers must attach all W-2s, 1099s, and other withholding statements to the front of the return. Attach all other schedules and forms in the sequence shown in the upper right-hand corner. Missing forms can delay processing or cause the IRS to send a request for additional documentation.

Claiming ineligible credits or deductions

Some taxpayers mistakenly claim credits or deductions they are not eligible for, such as education credits, home office deductions, or certain business expenses. Eligibility often depends on income limits, filing status, and documentation. The IRS has increased automated checks to detect ineligible claims, and improper claims can result in penalties or being barred from claiming the credit for up to ten years.

Forgetting to sign and date the return

Unsigned paper returns are considered invalid and will be returned unprocessed. Both spouses must sign a joint return. E-filed returns require a self-selected PIN or adjusted gross income (AGI) from the prior year to verify identity.

Postage problems

When mailing a paper return, use sufficient postage based on weight. Insufficient postage can result in the return being sent back, potentially causing you to miss the filing deadline.

Incorrect or missing tax payments

If paying by check, make it payable to “United States Treasury” and include your name, address, daytime phone number, SSN, tax form number, and tax year on the memo line. The IRS also offers secure electronic payment options through IRS Direct Pay and the Electronic Federal Tax Payment System.

Additional tips to avoid problems

  • Use the IRS “Where’s My Refund?” tool or IRS2Go app to track refund status instead of calling the IRS unless specifically directed.
  • Consider filing as early as possible to reduce the risk of tax-related identity theft.
  • Keep a complete copy of your return and all supporting documents for at least three years.
  • Use the latest tax software updates or IRS instructions for accurate rates, thresholds, and inflation adjustments.
  • Double check dependent information and confirm you are the correct person eligible to claim them, especially in cases of shared custody.