What are the common tax mistakes? 10 costly errors and how to avoid them (Infographic)

• The most common tax mistakes are wrong Social Security numbers, incorrect filing status, math errors, and unreported income.
• Other frequent issues include missing signatures, incorrect bank account numbers, and overlooking valuable credits and deductions.
• E-filing with trusted tax preparation software reduces math errors, speeds up refunds, and lowers the overall error rate.  
• The “$600 rule” usually refers to information returns like Forms 1099; for 2025, Form 1099-K again uses the higher $20,000 and 200 transactions threshold, but you must still report all taxable income even if you do not receive a form.  
• To avoid common tax mistakes, double check Social Security numbers, confirm the correct filing status, match every W-2 and 1099 to your records, review bank account numbers for direct deposit, and file before the deadline.
• Using pdfFiller to organize, complete, and e-sign IRS tax forms helps businesses centralize tax documents, reduce manual data entry, and maintain compliant digital records.

What are the common tax mistakes?

When people ask “what are the common tax mistakes?”, they usually mean the recurring errors that cause delayed refunds, extra penalties, or IRS notices.

In plain language, common tax mistakes are avoidable errors on your federal income taxes, such as:

• Typing a wrong Social Security number
• Choosing the wrong filing status
• Misreporting taxable income
• Miscalculating tax credits and tax deductions
• Forgetting to sign the return
• Using wrong bank routing and account numbers for direct deposit
• Filing late or not paying enough to cover your tax liability

These tax mistakes to avoid show up year after year in IRS statistics and IRS notices. 

For B2B teams that manage many taxpayers’ documents—employees, contractors, or clients—these mistakes often start as simple document issues: missing forms, outdated templates, or inconsistent data entry. That is exactly the gap digital tools like pdfFiller aim to close by standardizing how you prepare, route, and sign tax forms.

Most common mistakes taxpayers make when filing returns

Click to enlarge the infographic

Top 10 IRS form errors people make (and how to avoid them)

Even small errors can cause big problems when it comes to your taxes. Here are the most common tax mistakes taxpayers make—and simple ways to fix them.

1. Wrong Social Security number
   One of the easiest tax mistakes to avoid—and still one of the most common. A mistyped Social Security number can cause identity mismatches and processing delays.
   Tip: Always verify each SSN against the Social Security card (for you and every dependent). If your team handles employee or contractor documents, store ID data in a secure, centralized system instead of spreadsheets or email.
2. Incorrect filing status
   Choosing the wrong filing status can change your tax bracket, standard deduction, and your final tax refund or balance due.
   Tip: Use the IRS filing status guidance or online tools to confirm whether you should file as Single, Head of Household, Married Filing Jointly, or Married Filing Separately before you submit.
3. Math errors
   Manual tax math often leads to IRS math-error notices, especially for tax calculation / other taxes and adjusted gross income / taxable income lines. Recent IRS data show more than a million math errors each year on individual returns.
   Tip: Use tax preparation software or e-filed returns that calculate totals and credits and deductions automatically.
4. Missing signatures
   An unsigned tax return is considered incomplete. The IRS treats it as if you never filed.
   Tip: Sign both the tax return and any e-file authorization forms. If you file a joint tax return, both spouses must sign—even if one spouse’s income is zero.
5. Incorrect bank information
   If your routing and account numbers are wrong, your refund or payment can be delayed or misdirected.
   Tip: Copy bank details directly from a check or your banking app, then double check them before finalizing your return.
6. Unreported income
   Side income (freelance, gig work, online sales) often gets missed. The IRS receives copies of many tax forms (such as W-2, 1099-NEC, and 1099-K) and matches them to your taxable income.
   Tip: Match every W-2, 1099, and other required forms to your records. Keep a separate log for cash payments, platform earnings, and capital losses.
7. Claiming ineligible dependents
   Claiming someone who does not meet the IRS dependent rules can trigger an IRS notice or audit.
   Tip: Review IRS dependent criteria carefully, especially for shared custody, adult children, or other relatives.
8. Missing deductions or credits
   Many taxpayers fail to claim all credits and deductions they qualify for, such as retirement contributions, education credits, or charitable contributions.
   Tip: Maintain a yearly checklist of valuable credits and common tax deductions and store proof (receipts, statements) in an organized digital folder.
9. Late filing or payment
   Filing after the filing deadline or paying late leads to penalties and interest.
   Tip: Plan ahead for tax day. If you cannot finish in time, file Form 4868 for an extension and pay as much as you can to reduce penalties.
10. Paper filing errors
    Paper returns have a higher error rate and take longer to process. By mid-March 2025, about 97% of individual returns received by the IRS were filed electronically, reflecting how strongly e-file has become the default.
    Tip: Switch to filing electronically through trusted tax software and use electronic signatures that follow ESIGN Act standards for legal validity.

What is the $600 rule?

The phrase “$600 rule” can be confusing because it is used in more than one context.

How the $600 rule works for 1099 forms

Traditionally, many businesses must issue Form 1099-NEC or Form 1099-MISC when they pay a non-employee $600 or more during the year. This applies to many contractors and vendors. That reporting rule is separate from the new 1099-K rules.

Key points:

• If you pay an independent contractor $600 or more, you generally must send them a 1099-NEC and also send a copy to the IRS.
• The contractor must report this income on their tax return as taxable income, even if the business forgets to send the form.

The $600 rule and Form 1099-K

In recent years, there has been a lot of discussion around a lower $600 reporting threshold for Form 1099-K, which reports payments from third-party apps and platforms. For the 2025 tax year, the law changed again:

• Under the One Big Beautiful Bill (OBBB), the IRS reinstated the $20,000 and 200 transactions threshold for Form 1099-K starting with the 2025 filing season.
• This means you will only receive a 1099-K if you both:
  • Have more than $20,000 in reportable payments and
  • Have more than 200 transactions through a given payment platform.

However, and this is critical:

You must report all taxable income on your return even if you never receive a 1099-K, 1099-NEC, or any other tax forms.

So, the “$600 rule” is really about when payers must report, not about when income becomes taxable. For compliance, B2B finance teams should:

• Track contractor and platform payments accurately throughout the year
• Keep copies of all 1099s and reconciliation reports in a secure document repository such as pdfFiller
• Coordinate with a tax professional when reporting rules change

What raises red flags with the IRS?

Most tax returns are processed automatically with no human review. But some patterns increase the chance that a return will be flagged or questioned.

Here are common red flags:

• Unreported or mismatched income
  • The IRS receives W-2, 1099, and 1099-K copies directly from payers and compares them to your filing. Large differences or missing forms can trigger a notice.
• Claiming dependents also claimed by someone else
  • When the same Social Security number appears on two returns as a dependent, one or both returns may be delayed or rejected.
• Very large or unusual deductions relative to income
  • For example, itemized deductions or losses that seem high for your reported income or tax bracket.
• Excessive business losses or capital losses
  • Repeated large losses, especially from side businesses with little real activity, can lead to more IRS questions.
• Inconsistent filing from prior years
  • Large unexplained swings in taxable income, filing status, or reported property taxes may prompt follow-up.
• Identity theft indicators
  • If a scammer files a fraudulent return using your SSN, the IRS may freeze related refunds while it investigates. Recent watchdog reports note that identity theft cases can take around 22 months on average to resolve.

For businesses, strong document controls reduce red flags. Use pdfFiller to standardize how staff collect W-9 forms, store prior-year returns, and prepare tax forms before they are sent to payroll, finance, or a tax professional.

What are the common tax traps?

Beyond obvious errors, there are common tax traps that quietly increase your tax burden or cause penalties.

Choosing the wrong filing status

• Filing as Married Filing Separately when a joint tax return would meaningfully reduce your combined tax liability
• Missing Head of Household when you qualify, which can lower your tax bracket and increase your standard deduction

Ignoring credits and deductions

• Not claiming tax credits such as the Child Tax Credit, education credits, or clean-energy credits
• Failing to itemize deductions when your mortgage interest, state and property taxes, and charitable contributions exceed the standard deduction

Under-withholding and surprise balances

• Not updating your W-4 after a raise, second job, or major life change
• Ending up owing more money than expected on tax day, plus penalties and interest

Poor recordkeeping

• Misplacing necessary forms from previous years
• Having no documentation for charitable contributions, business expenses, or capital losses

Real IRS filing data: why these traps matter

IRS statistics show how common calculation and reporting traps are:

• The IRS reports more than 1 million math-error notices each year on individual returns, with a large share tied to tax calculation and adjusted gross income / taxable income lines.
• IRS “get ready” guidance stresses that planning ahead—organizing tax records and understanding tax laws—reduces errors and speeds up refunds. 

When your organization handles complex tax workflows—such as employee relocations, reimbursements, or stock-based pay—these traps multiply. Centralizing your tax forms in pdfFiller helps ensure everyone is working from the same up-to-date templates and instructions.

How does e-filing reduce common tax mistakes?

Electronic filing helps many taxpayers avoid errors before the IRS ever sees the return.

IRS data for the 2025 filing season show that about 97% of individual returns received by mid-March 2025 were e-filed, and most refunds went out via direct deposit.

The benefits of e-filing

E-filing offers built-in safeguards that reduce errors, prevent rejections, and ensure faster refunds:

• Automatic math checks
  Tax software handles calculations, reducing math errors and other common mistakes.
• Field validation
  Many systems validate SSNs, account numbers, and routing numbers before submission.
• Faster refunds
  E-filed returns with direct deposit are typically processed faster than paper returns mailed with checks.
• Instant acknowledgment
  You receive a confirmation when the IRS accepts your return, which helps you plan ahead and track your financial goals.
• Better records
  Digital copies of returns and supporting documents are easier to store, search, and share securely.

For individuals who qualify, the IRS also supports free e-file options through the IRS Free File program.

Comparison: paper filing vs e-filing vs working with a tax professional

Instead of a table, here is a quick comparison list:

Paper filing

• Pros: Works without a computer; familiar to some taxpayers
• Cons: Higher error rate, slower refund, risk of lost mail, need to buy enough postage; more manual work for both taxpayer and IRS

E-filing with tax software

• Pros: Lower error rate, automatic calculations, faster refunds, built-in checks; often easier to double check entries; good for many taxpayers
• Cons: You must understand your inputs; complex issues may still require advice

Working with a tax professional

• Pros: Expert help with complex situations, planning for financial goals, strategy across prior years and future years; professional finds mistakes to avoid and valuable credits
• Cons: Higher direct cost; still requires you to collect and provide required forms

In practice, many businesses use a mix: tax software plus a tax professional, plus tools like pdfFiller to streamline how staff fill, e-sign, and store the underlying tax documents.

How can you protect your identity during tax season?

Identity theft is now one of the biggest service challenges for the IRS. Recent reports show that identity theft cases can take around 22 months on average to resolve, leaving taxpayers waiting a long time for their refunds.  

Safeguard your personal information

To reduce your risk:

• Request an IRS Identity Protection PIN (IP PIN)
  • An IP PIN is a 6-digit code that helps the IRS confirm that it is really you filing the return.
• Limit where you share your SSN
  • Do not send your Social Security number or tax forms over unencrypted email or messaging apps.
• Use secure digital tools
  • Store tax documents in a secure, access-controlled platform like pdfFiller instead of on shared drives or personal devices.
• Monitor your IRS account
  • Create an account on the IRS site and check for unexpected returns or notices.

pdfFiller supports secure document workflows with role-based access and detailed audit trails. That helps B2B organizations reduce exposure of sensitive tax data across multiple teams and regions.

How can pdfFiller help you avoid tax mistakes?

While pdfFiller cannot replace a tax professional, it can make it much easier for your team to avoid common mistakes when working with tax paperwork.

Here is how pdfFiller fits into a modern, compliant tax workflow:

• Access up-to-date IRS forms digitally
  • Work with the latest versions of Form 1040, W-9, W-4, and other tax forms directly in your browser.
  • Reduce the risk of using outdated documents or missing required forms.
• Standardize data entry
  • Create reusable templates with predefined fields (name, SSN, filing status, income, property taxes, etc.).
  • Limit free-text entry where possible to cut down on inconsistent data.
• Support compliant e-signatures
  • pdfFiller’s e-signature workflows are designed to align with U.S. ESIGN Act standards, which give electronic signatures the same legal effect as handwritten signatures in most commercial contexts.  
• Simplify collaboration with tax professionals
  • Share forms securely with your tax professional so they can review, comment, or request changes—without email attachments or version confusion.
  • Use guided signature requests to ensure all parties sign in the correct sequence.
• Create reliable audit trails
  • Track who viewed, edited, or signed each document and when.
  • This helps if you ever need to show how you prepared specific forms in prior years.
• Integrate with your broader tech stack
  • Use pdfFiller to keep tax documents aligned with HR, finance, and compliance workflows—supporting better planning for financial goals and fewer last-minute surprises during tax season.

Quick checklist: how to avoid the most common tax mistakes

Use this short, repeatable checklist each tax season:

• Gather all necessary forms (W-2, 1099, 1099-K, 1098, prior-year return) before you start
• Confirm your correct filing status using IRS tools or guidance
• Enter and double check every Social Security number and ITIN
• Match each income line to a form (no unreported income)
• Review tax deductions and tax credits to avoid missing eligible items
• Verify routing and account numbers for direct deposit
• Review math and totals, or let tax preparation software calculate them
• Sign the return and any authorization forms (both spouses on a joint return)
• File before the filing deadline, or request an extension if needed
• Store signed returns and key documents securely in pdfFiller

Final thoughts: Ready to file with fewer mistakes?

Understanding what are the common tax mistakes? is the first step. Designing a simple, repeatable process to avoid them is the second.

From wrong SSNs and math errors to unreported side income and missed valuable credits, most tax mistakes are preventable with better tools and habits. For B2B organizations that manage many tax-related documents, the risks multiply—but so do the opportunities to improve.

pdfFiller helps your teams:

• Work from current, accurate tax templates
• Standardize how information is collected and reviewed
• Capture compliant e-signatures and maintain complete audit trails

Start a free trial of pdfFiller and see how a modern, digital document workflow can help your organization avoid common tax mistakes, keep cleaner records, and move through every tax season with more confidence.

Glossary

• Adjusted Gross Income (AGI): Your adjusted gross income is your total income from all sources (wages, interest, business, etc.) minus certain adjustments, such as traditional IRA contributions or student loan interest. AGI is the starting point for many credits and deductions.
• Taxable income: This is the amount of income that is actually subject to tax after subtracting the standard deduction or itemized deductions and certain other exclusions. Your tax bracket is based on your taxable income.
• Filing status: Your filing status defines how you file your return—Single, Married Filing Jointly, Married Filing Separately, Head of Household, or Qualifying Surviving Spouse. It affects your tax bracket, standard deduction, and eligibility for some tax credits.
• Tax credit: A tax credit directly reduces the amount of taxes you owe. For example, a $500 credit usually reduces your tax liability by $500, assuming you are eligible.
• Standard deduction: A fixed dollar amount that reduces the income you are taxed on, based on your filing status. Many taxpayers take the standard deduction instead of itemizing, especially if their deductible expenses are relatively low.