Top Tax Filing Mistakes—and How to Avoid Them

Making mistakes on your tax return can cost you money. You may miss out on a larger refund than you claimed or wind up owing more taxes plus interest and penalties. You could invite an audit from the Internal Revenue Service (IRS). The best defense against results like these is a good offense: Avoid errors on your return.

Common Tax Filing Mistakes

Tax laws are complex. U.S. tax statutes and IRS regulations included more than 10 million words as of 2015, according to the Tax Foundation. The mistakes that taxpayers make on their returns tend to be fairly simple, however, even though the rules are complicated. Here are 10 of the most common and what you can do to avoid them.

1. You Blow the Basics

Confirm that your name and those of your dependents are spelled correctly and that Social Security numbers are correct. And be sure to select the correct filing status for your situation.

You could file as single if you’re unmarried but you may qualify for more favorable tax rates and other tax perks if you meet the requirements to qualify as head of household or qualifying widow(er) with a dependent child. And married couples may pay less tax overall in some cases if they file separately rather than jointly.

2. You Don’t Enter Information As It’s Been Reported

Wages, dividends, bank interest, and other income you earned that was reported on an information return such as a W-2, 1099, or K-1 should be entered carefully. These forms have also been submitted to the IRS and the government’s computers are looking for this information to match.

Contact the business that made the payment to you, such as your employer, and request a corrected form if you have to dispute what’s been reported. You can call the IRS at (800) 829-1040 to initiate a Form W-2 complaint if you don’t receive a corrected form by the end of February.

3. You Don’t Enter Items on the Correct Lines

Make sure your entries appear in the correct places when you enter them on your tax forms. Don’t put your tax-free IRA rollover on the line meant for taxable IRA distributions. Using tax software should help prevent this issue but always double check where items appear on your final return before clicking the submit button.

4. You Automatically Take the Standard Deduction

Itemizing requires more effort, receipts, and other proof than relying on the standard deduction but you could lose money by automatically taking the standard deduction. Check which alternative gives you the greater write-off. It will depend on the total of the itemized deductions you qualify for. Is it more than the standard deduction you’re entitled to claim for your filing status?

The standard deductions nearly doubled beginning in 2018 under the Tax Cuts and Jobs Act (TCJA) so itemizing is less likely to save you money, at least through 2025. The TCJA is set to expire at the end of 2025 and standard deductions are slated to fall back to their old levels beginning in 2026 unless Congress intervenes.

It never hurts to run the numbers both ways in any case. Most tax software automatically calculates which method is most beneficial for you.

5. You Don’t Take Write-Offs You’re Entitled to Take

Some may fear that a specific deduction is an audit red flag so they shy away from it. There continues to be a belief that claiming a home office deduction can trigger a tax audit. This probably isn’t true given that the IRS created a simplified deduction alternative to writing off these expenses.

It’s wise to take the deduction if you meet its tax law requirements. Most employees can’t claim it, however. You must be an independent contractor and self-employed or qualify for one of the few other exceptions. Employees generally can’t deduct unreimbursed home office expenses as a miscellaneous itemized deduction on Schedule A.

6. You Forgot Your State Healthcare Individual Mandate

The Affordable Care Act (ACA) individual mandate required that you pay a penalty fee for every month that you and/or your family lacked qualifying health coverage but it was eliminated in 2019. Some states have their own health insurance mandates, however, so be sure you know what your state requires.

Five states and the District of Columbia have health insurance mandates as of the 2024 tax year:

• California
• District of Columbia
• Massachusetts
• New Jersey
• Rhode Island
• Vermont

7. You Don’t Check for Typos

It’s easy to transpose a number or leave out a digit and this is a mistake that can distort the information you’re reporting. Say you contributed $5,200 to your individual retirement account (IRA) but you inadvertently entered $2,500 as the deduction on your return. You’ve cheated yourself out of a $2,700 deduction that will cost you $648 more in taxes if you’re in the 24% tax bracket.

8. You Make Math Mistakes 

Math errors are among the most common tax filing mistakes, according to the IRS. They can range from basic addition and subtraction to more complex calculations. Always double-check your math or use tax preparation software that does the math for you.

Check the IRS instructions if you have to enter a negative number. Some forms prefer parentheses but others use the minus symbol. This ensures that IRS computers read the negative entry correctly. Enter a loss of $500 on your return as ($500) and not -$500 if ($500) is required.

9. You Don’t Tell the IRS How to Handle Your Refund

Be proactive about what you want the government to do with your refund if you overpaid your taxes and you’re due a refund. The U.S. Treasury will send you a paper check through the mail if you don’t do anything.

Add your bank account information including your account number and the routing number to get your refund much faster. The refund will be deposited directly into your account. You can opt to split your refund into as many as three accounts or use it toward next year’s estimated taxes, as contributions to various retirement accounts, or to buy U.S. Treasury marketable securities. The instructions for Form 8888 explain your options.

10. You Make Payment Mistakes

Make sure that your payment is correctly credited to you if you owe taxes. Include Form 1040-V with your check whether filing electronically or a paper return. You can pay through the government’s free payment sites, EFTPS.gov or Direct Pay, or by credit or debit card through an IRS-approved payment provider.

You can amend your return using Form 1040-X, the Amended U.S. Individual Income Tax Return, if you made an error on it.

The Bottom Line

Always be sure to sign your tax return. It’s not valid unless you’ve signed. Keep a copy of your signed return along with proof of filing such as an acknowledgment that your e-filed return has been accepted by the IRS or a certified receipt for a paper return sent by mail.

Having this proof helps protect you from any IRS claims that you filed late or not at all. Your past tax returns will also come in handy when you file future tax returns or if you have to file an amended return.