Tax filing mistakes range from minor typos that delay processing to more significant errors that trigger an audit or a missed refund. Most fall into a fairly predictable set of categories, which makes them worth checking for specifically before submitting a return.

Simple data entry errors

An incorrect Social Security number, a misspelled name that doesn't match Social Security Administration records, or a wrong bank account number for direct deposit are all common and entirely avoidable errors that can delay processing or, in the case of a wrong bank account, send a refund to the wrong place. Double-checking these specific fields before submitting is a simple, worthwhile habit.

Choosing the wrong filing status

Filing status (single, married filing jointly, married filing separately, head of household) affects both the standard deduction amount and tax bracket thresholds significantly. Head of household status, in particular, has specific eligibility requirements that are sometimes missed or, alternatively, incorrectly claimed by taxpayers who don't actually qualify — worth reviewing the specific requirements rather than assuming.

Missing a 1099 form because it arrived by mail after e-filing already began, or because it never arrived and wasn't followed up on, is one of the more common reasons the IRS later flags a return for a discrepancy.

Forgetting income from all sources

Freelance income, interest from a savings account, dividend income, or a side gig payment platform report can all generate a 1099 form, and forgetting to include income reported on a 1099 the IRS also received is a common trigger for a discrepancy notice later, since the IRS cross-references reported income against submitted returns.

Missing deductions and credits

Failing to claim eligible deductions or credits doesn't trigger an audit, but it does mean overpaying — common missed items include certain educator expenses, student loan interest, retirement contribution credits for lower and middle incomes, and energy-efficiency home improvement credits, all of which are sometimes overlooked simply because the taxpayer didn't know they existed.

Math errors and outdated software

Manual math errors are less common now with tax software handling calculations, but using outdated software or forms from a prior tax year (with different limits and brackets) can introduce errors that look like simple math mistakes but actually stem from using the wrong year's rules.

Missing the filing deadline (or the extension deadline)

Filing late without requesting an extension, or requesting an extension but forgetting that an extension to file is not an extension to pay any tax owed, are both common and costly mistakes — an extension moves the filing deadline but generally still requires an estimated payment by the original deadline to avoid penalties and interest.

Not keeping adequate records

Claiming deductions or credits without retaining supporting documentation (receipts, mileage logs, donation records) creates real risk if the return is later reviewed or audited — the IRS generally recommends keeping tax records for at least three years, and longer in certain situations involving significant underreported income or claimed losses.

Try thisBefore submitting a tax return, create a simple checklist: confirm all W-2s and 1099s received match what's entered, confirm personal information matches Social Security records exactly, confirm direct deposit bank details are correct, and confirm the filing status genuinely fits your situation. Running through this list takes a few minutes and catches the majority of common errors.

This article covers general categories of common tax mistakes, not specific tax advice for an individual situation — a tax professional or reputable tax software can provide guidance specific to a particular year's tax law and an individual's complete financial picture.