The biggest tax mistakes to avoid include missing filing deadlines, entering incorrect Social Security numbers or banking information, and failing to report all income sources. Other critical errors involve choosing the wrong filing status, miscalculating math, overstating deductions, and filing too early before all documents are received.
Avoid These Common Tax Mistakes
Contributions to pension or retirement plans — such as to 401(k)s and IRAs — are either not taxed when they are received but are taxed when withdrawn from accounts, or for Roth-style plans, contributions are taxed when received and are tax-free at the time of withdrawal.
Business titans tend to take their compensation as shares in publicly traded companies and privately held businesses, as well as investments in “pass-through” companies with special tax rules.
Many business expenses are 100% deductible, including advertising, employee wages, rent, supplies, and certain business meals like company parties or meals for the public, while personal deductions like student loan interest or charitable donations (depending on the type) can also be fully deductible for individuals. The key is that the expense must be "ordinary and necessary" for your trade or business or meet specific IRS criteria, often differentiating from the 50% rule for client meals.
Common Tax Deductions You Can Claim Without Receipts
The "20k rule" refers to the traditional IRS threshold for reporting income from payment apps and online marketplaces on Form 1099-K: over $20,000 in gross payments AND more than 200 transactions in a calendar year. While a law (the American Rescue Plan) temporarily lowered the threshold to $600, recent legislation, the One Big Beautiful Bill Act (OBBBA) (OBBBA), has reinstated the $20,000/200-transaction rule for tax years starting in 2025, providing relief for casual sellers and gig workers.
Reporting cash payments
A person must file Form 8300 if they receive cash of more than $10,000 from the same payer or agent: In one lump sum. In two or more related payments within 24 hours. For example, a 24-hour period is 11 a.m. Tuesday to 11 a.m. Wednesday.
You generally need to file a U.S. federal tax return if your gross income for Tax Year 2025 (filed in 2026) is above a certain threshold, which varies by filing status and age, for instance, $15,750 for single filers under 65, while self-employed individuals must file if they earn $400 or more in net earnings. Thresholds increase for married couples and those 65 or older, but you might still need to file to claim a refund or refundable credits even if below the income limit.
The IRS uses a combination of automated and human processes to select which tax returns to audit. Not reporting all of your income is an easy-to-avoid red flag that can lead to an audit. Taking excessive business tax deductions and mixing business and personal expenses can lead to an audit.
Common traps include taxes on Social Security benefits, Medicare surcharges, required minimum distributions (RMDs), real estate sales and estimated quarterly tax payments. With some knowledge, though, you can more effectively steer clear of these potential pitfalls.
Federal tax law offers several opportunities to lower your taxable income:
You can write off common expenses like student loan interest, retirement contributions (IRA/401k), self-employed health insurance, and business-related costs (home office, mileage, supplies) if you're an employee or self-employed, but itemizing deductions for things like medical expenses (over 7.5% AGI), mortgage interest, and charitable donations only pays off if it exceeds the Standard Deduction. Self-employed individuals have many more write-offs, including professional dues, business meals, and equipment, but always keep meticulous records.
The $20,000 limit under the measures applies on a per asset basis, so small businesses can instantly write off multiple assets. Assets valued at $20,000 or more can continue to be placed into the small business pool and depreciated at 15% in the first income year and 30% each income year after that.
The IRS allows taxpayers to deduct up to $3,000 of realized investment losses ($1,500 if married filing separately) against ordinary income each year. This deduction applies only to losses in taxable investment accounts and must be realized by December 31st to count for that tax year.
Expensing an item may bring in more money in the short term, but once you have expensed it, it does not qualify for write-offs on future tax returns. Depreciating an asset may result in less money upfront, but could result in fewer taxes owed in the future.
The IRS doesn't have a specific dollar limit for hobby income; instead, it focuses on profit motive: if you intend to make a profit, it's a business, but if it's for fun, it's a hobby, and you must report all income but can't deduct losses. Key is that you report all hobby income on Form 1040 as "other income," and if net earnings from self-employment are $400 or more, you owe self-employment tax, even if it's a side gig. The main difference from business is that you can't deduct hobby expenses (under current law) and must report all profits.