Many tax filing mistakes are avoidable, but even a small error can delay a refund, change the tax owed, or trigger an IRS notice. A transposed digit, a missing form, or the wrong filing status is enough to cause one.
The good news is that the same errors show up year after year. Once you know what they are, you can check for them before you file.
This guide covers the mistakes that affect individual filers and the ones that catch small business owners, in one place. It ends with what a preparer actually does to prevent them. If you would rather hand the return off, see our tax preparation services.
Names, identification numbers, and bank details
Start with the simplest errors, because they are the ones that stop a return before anything else is considered. The IRS lists inaccurate names and Social Security numbers, missing signatures, and incorrect bank details among the common problems it sees.
A small data-entry mistake can reject a return or delay a refund. Check that every name and Social Security number matches the Social Security card, for you, your spouse, and every dependent. Names that changed after a marriage or divorce need to match Social Security records before you file.
Review bank routing and account numbers before requesting direct deposit. A wrong digit can send a refund to the wrong place, and recovering it is slow. Both spouses must normally sign a joint paper return, and an unsigned return is not valid.
Wage and income figures deserve the same care. Enter what the form says rather than what you remember, and check the entry against the document itself.
Filing status errors
Filing status is one of the errors the IRS names directly. Some taxpayers claim the wrong status, such as head of household instead of single (IRS). Status affects your standard deduction, your bracket, and your eligibility for several credits, so an error here changes the whole return.
Head of household has detailed requirements. You generally must be unmarried or considered unmarried, pay more than half the cost of keeping up the home, and have a qualifying person live with you for more than half the year. A special exception may apply when the qualifying person is your dependent parent. Supporting someone financially is not enough on its own.
Married couples run into a different question. Separate returns may make sense in limited situations, but the comparison can be complex. In Texas, community-property rules may require spouses filing separately to divide community income and deductions and attach Form 8958. If one spouse itemizes, the other generally must itemize too. It is worth comparing carefully rather than assuming.
Life changes are the usual trigger. A marriage, divorce, death, or a child moving out can change your correct status, and the status that was right last year may not be right this year.
How to avoid it
Re-check your status every year rather than carrying last year’s forward. If your household changed at all, work through the requirements for each status you might qualify for, or ask your preparer to compare the options.
Missed income and missing 1099s
Missing or inaccurate income is a common filing problem. The reason is simple: the agency receives copies of the same forms you do, so a missing form is easy to spot from their side.
A related mistake is filing too early. The IRS specifically warns against filing before you are certain you have received all your reporting documents, because it risks an error that causes a processing delay (IRS). W-2s and many 1099s arrive at the end of January, and some forms come later.
The income people forget tends to be the income that does not come from a main job:
- Freelance or side work reported on Form 1099-NEC.
- Business payments received through cards, payment apps, or online marketplaces, including amounts reported on Form 1099-K.
- Interest and dividends on Forms 1099-INT and 1099-DIV, including small amounts.
- Retirement or brokerage activity on Forms 1099-R and 1099-B.
- Unemployment compensation, which is generally taxable.
- Cash income that never generates a form at all, which is still reportable.
A Form 1099-K can also include amounts that are not taxable, such as gifts, repayments of shared personal expenses, or certain personal-item sales. Compare it with your records rather than reporting the gross total automatically. Business income is reportable even when no Form 1099-K arrives.
Corrected forms cause a second wave of problems. If an issuer sends a corrected 1099 after you have filed, your return no longer matches their records, and you may need to amend it.
How to avoid it
Keep a list of every income source from last year and check each one off as the form arrives. Wait until the list is complete before filing. If a form is missing, contact the issuer rather than guessing at the number.
Deduction and credit mistakes
The IRS also flags errors in figuring credits and deductions, including the Earned Income Tax Credit, the Child and Dependent Care Credit, and the standard deduction (IRS). Mistakes run in both directions. Some people claim things they do not qualify for, and others miss benefits they are entitled to.
Another mistake is itemizing when the standard deduction would produce a better result, or taking the standard deduction without comparing the available itemized deductions. Since the standard deduction rose, fewer filers benefit from itemizing, but it still pays to compare rather than default.
Missing documentation is the other half of the problem. A deduction you cannot support is a deduction you may lose if anyone asks. Charitable contributions, business use of a vehicle, and home office costs all need records behind them.
Newer provisions deserve extra care, because nobody has years of practice applying them. New forms and new rules tend to produce more errors in their first year, so check eligibility carefully rather than assuming a deduction applies to you.
2026 TAX FILING UPDATE
For the 2026 filing season, the IRS introduced Schedule 1-A for recently enacted deductions, including deductions related to tips, overtime, car loan interest, and an enhanced deduction for seniors (IRS). If any of these may apply to you, confirm the current eligibility rules before claiming them.
How to avoid it
Do not claim a credit because you heard you qualify. Check the actual requirements, keep the records that support each claim, and be especially careful with anything new. If a deduction sounds too good to be true, verify it before it goes on the return.
Small business tax mistakes
Business owners have all the individual pitfalls plus a set of their own. These are the ones that come up most.
Mixing personal and business money
Running personal spending through the business account is the root cause of many other errors. It inflates expenses, muddies your books, and makes every deduction harder to defend. A separate business account and card solves most of it.
Missing estimated tax payments
If you are self-employed or receive income without enough withholding, you may need to make estimated tax payments during the year. Check your expected balance and the IRS safe-harbor rules before deciding. Missing required payments can lead to an underpayment penalty even when you pay in full at filing, which surprises people in their first profitable year.
Weak records and missing receipts
A bank statement shows that money moved, but it may not show why. For expenses that are not self-explanatory, note the business purpose and the people or project involved. This matters most for meals, travel, vehicle use, and mixed-purpose purchases.
Home office and vehicle errors
Both deductions are legitimate and both are commonly miscalculated. A home office normally requires regular and exclusive business use. Different rules may apply to qualifying daycare facilities and spaces used to store inventory or product samples. Vehicle deductions require a record of business versus personal mileage, kept as you go rather than reconstructed later.
Worker classification
Treating an employee as a contractor is a costly error, and it is decided by the facts of the relationship rather than by the label on a contract. Our guide to worker classification covers the tests the IRS and the Texas Workforce Commission apply.
Missing the business return deadline
Business entities do not all share the individual deadline. S corporations and partnerships generally file earlier in the spring than individual returns, and missing that date can bring a penalty calculated per partner or shareholder per month. Confirm the date that applies to your entity.
Forgetting the Texas filings
Texas does not levy a personal state income tax, which leads some owners to assume there is nothing to file at the state level. Many Texas entities have annual franchise-related filing duties. An entity at or below the applicable no-tax-due threshold generally does not file a No Tax Due Report, but it may still need to file a Public Information Report or an Ownership Information Report. Required Franchise Tax Reports are generally due May 15.
Deadline and extension errors
Individual returns are generally due in mid-April. In the most recent filing season, the IRS opened on January 26, 2026 and set a deadline of April 15, 2026 for tax year 2025 returns (IRS). When the date falls on a weekend or holiday, it shifts, so confirm the date for the season you are filing in.
The biggest misunderstanding in this area is what an extension actually does. An extension gives you more time to file. It does not give you more time to pay. If you owe, the payment is still due on the original deadline, and interest and penalties can accrue from that date even with a valid extension on file.
Two smaller errors show up alongside it. People assume no refund means no need to file, when filing may still be required or beneficial. And people who cannot pay sometimes do not file at all, which is usually the worse choice, because the failure-to-file consequence is generally steeper than the failure-to-pay one.
How to avoid it
Put the deadline in your calendar with a reminder several weeks ahead. If you will be late, file the extension and pay your best estimate of what you owe by the original date. If you cannot pay in full, file anyway and ask about payment options.
How a preparer helps prevent these
Tax software can catch calculation and missing-field errors. A qualified preparer can also ask follow-up questions and help apply the rules to your situation. Neither option guarantees an error-free return.
A good preparer asks about the things you would not think to mention. A new dependent, a side business, a house sale, a move between states, or a change in marital status all affect the return, and none of them announce themselves on a form.
An experienced preparer may also recognize current-year issues that are easy to miss. Rules change, new provisions arrive, and a first year of anything tends to produce more errors.
Clean books make their work faster. When your records are current and reconciled, the preparer spends time on the return rather than on organizing your year. That may reduce the time they need, although the final fee still depends on the preparer and the complexity of your return.
Using a preparer does not remove your responsibility. Review the return before it is filed, ask about anything you do not understand, and make sure the numbers match what you know about your year.
Common questions
What happens if I make a mistake on my return?
It depends on the type. The IRS corrects some simple errors and will notify you. Other returns are rejected so you can fix and resubmit. Larger issues, such as missing income, generally bring a notice explaining what needs to change and whether more tax is due.
How do I correct a return I already filed?
Amended individual returns are generally filed on Form 1040-X. Not every error requires an amendment, so check whether one is needed before filing it, and talk to a preparer if the change is significant.
Does an extension give me more time to pay?
No. An extension moves the filing deadline, not the payment deadline. Estimate what you owe and pay it by the original date to limit interest and penalties.
I did not receive a 1099. Do I still report the income?
Yes. Income is generally reportable whether or not a form arrives. Contact the issuer for a missing form, and keep your own records so you can report the amount accurately.
How long should I keep my tax records?
Three years is a common federal retention period, but it is not universal. Employment tax records generally need at least four years, and property, bad-debt, and certain other records may need longer.
Book a free tax consultation
Tax by Lonestar prepares returns for individuals and small businesses in Allen and across Collin County.
In a free consultation, we look at your situation, flag anything that needs attention before filing, and explain what your return will involve. Contact us to set one up.
This guide is general information, not tax advice. Tax rules change and depend on your situation. For advice on your return, talk to a qualified tax professional, accountant, or CPA.
