5. Wrong Forms Determining which form(s) you need to file can be even more confusing than the math. The IRS suggests you use the simplest form that fits your situation—which is true most of the time. The more complicated forms also offer more ways to take deductions and that could increase your refund or lessen what you owe.
6. Wrong Filing Status Using the wrong filing status can affect your entire return and could even amount to fraud. The good news is that you can file an amended return if you realize your mistake after you’ve sent your forms.
7. Missed Deductions Even if you file the most basic tax return, you may qualify for deductions on things like student loan interest or adult education. This is where it pays to do your homework. Or at least use filing software like TurboTax which can alert you to possible deductions.
Read Related: Where to Turn for Free Tax Help