TL;DR Summary:
- Filing Errors Delay Refunds: Simple math errors, incorrect Social Security numbers, or misspelled legal names cause automated IRS rejections and processing delays.
- Unreported Income Triggers Audits: Omitting 1099 gig income, investment dividends, or side-hustle earnings can trigger IRS automated notice matching penalties.
- Missed Missouri Deductions: Forgetting charitable contributions, property tax credits, or local write-offs leaves money on the table.
- Penalty Risks: Missing the April 15 deadline without filing an extension incurs late-filing penalties up to 25% of uncollected tax balance.
- Professional Guidance: Working with a local CPA prevents compliance errors. Contact STL Tax or call our Gravois Road office for expert preparation.
Preparing your tax return can feel stressful. Whether you are filing an individual Form 1040, reporting self-employment income from a side business in South City, or managing business taxes across Greater St. Louis, minor oversight can lead to severe consequences.
Every year, thousands of Missouri residents face delayed refunds, unexpected tax bills, or IRS audit notices simply because of preventable filing errors.
Understanding the most common tax preparation mistakes allows you to protect your wallet and stay fully compliant with federal and state tax laws.
1. Basic Informational and Typos
The IRS relies on automated electronic scanning to verify tax returns. If the information on your return does not match official government records exactly, your tax return will be flagged or rejected immediately.
Common Informational Errors Include:
- Misspelled Legal Names: Using a maiden name after marriage or leaving off a hyphenated last name before updating records with the Social Security Administration.
- Incorrect Social Security Numbers (SSNs): Transposing digits in your SSN, spouse’s SSN, or dependent IDs.
- Banking Direct Deposit Routing Numbers: Inputting a wrong routing number can result in your refund check being mailed late or misdirected.
Local Example: If you moved from St. Charles to an apartment in Tower Grove South, filing without updating your address or ensuring your name matches your Social Security card will freeze your Missouri tax refund.
2. Math and Math-Calculation Errors
Even with modern digital tax software, manual data entries can cause arithmetic slip-ups. Incorrectly entering figures from box 1 of your W-2 or messing up standard deduction math directly alters your taxable income calculation.
The IRS will correct obvious math errors, but these corrections often result in an adjusted tax bill, interest charges, or reduced refund amounts.
3. Leaving Out Secondary Income Sources
With the rise of side hustles and digital platforms, income tracking has gotten more complex. You are required to report all taxable income, even if you did not receive an official tax form in the mail.
Frequently Forgotten Income Sources:
- Gig Economy Earnings: Rideshare driving, food delivery, or freelance contracting reported on Form 1099-NEC or 1099-K.
- Interest and Dividends: Taxable interest from local credit unions or online high-yield savings accounts.
- Crypto and Asset Sales: Selling cryptocurrency or stock holdings.
- Out-of-State Income: Earning income across state lines (such as commuting across the river to Illinois).
Case Study: A freelance graphic designer based in Maplewood failed to report $3,500 earned from short-term freelance contracts because no single client paid over $600. The IRS match program caught the discrepancy via payment processor reports, issuing a CP2000 notice requiring back taxes plus failure-to-pay penalties. Reporting all gross income prevents these automated IRS notices.
4. Overlooking Eligible Deductions and Charitable Receipts
Taxpayers frequently miss out on money they are legally allowed to keep. Failing to keep proper documentation or neglecting local Missouri credits is essentially turning down free cash.
Deductions Frequently Missed:
- Charitable Donations: Cash contributions, donated household goods to local St. Louis non-profits, or out-of-pocket volunteer expenses.
- State & Local Tax Credits: Eligible elderly or disabled residents often miss out on the Missouri Property Tax Credit (Circuit Breaker).
- Unclaimed Business Expenses: Small business owners frequently forget to track home office deductions, mileage logbooks, or professional subscriptions.
To claim write-offs safely, always keep receipts and records organized. If you get audited by the IRS or the Missouri Department of Revenue, clear records are your best protection.
5. Missing Tax Deadlines Without an Extension
The standard federal and state individual tax deadline is April 15th. Missing this deadline without submitting a formal extension request (Form 4868) leads to automatic IRS penalties.
- Failure to File Penalty: 5% of the unpaid taxes for each month or part of a month that a tax return is late (up to 25%).
- Failure to Pay Penalty: 0.5% per month on unpaid tax balance plus interest.
If you cannot file on time, submitting an extension gives you until October 15th to file your paperwork. However, an extension to file is not an extension to pay taxes owed.
Don’t Let Filing Mistakes Cost You Money
Filing your taxes accurately requires attention to detail, proper timing, and a clear understanding of federal and state tax laws.
Instead of taking risks with your tax refund or facing IRS penalties, let the experienced CPAs at STL Tax handle your tax preparation. We ensure every line item, deduction, and credit is maximized and error-free.
Call our St. Louis office today at (314) 645-1614 or schedule your tax preparation appointment online.
