As the April 15 tax filing deadline approaches, many individuals rush to file their taxes, often making simple yet costly mistakes. According to a report by GOBankingRates, these errors can lead to losses ranging from $500 to $2,000 annually. One major mistake is thinking about taxes only once a year, which can cause taxpayers to miss out on valuable deductions and credits. On average, Americans overpaid about $3,200 in federal taxes last year due to lack of planning. Another common error is failing to track deductions properly, such as donations and medical expenses, which can only be claimed if there is adequate proof. Additionally, incorrect reporting of investment income, particularly from stock options or restricted stock units, can increase capital gains taxes. Freelancers and those with side incomes must also be aware of quarterly estimated tax payments to avoid penalties. Lastly, basic errors like typos and miscalculations can delay refunds and lead to IRS notices. The good news is that all these mistakes can be avoided with careful planning and attention.