Most people have the same filing status and number of dependents as the previous year, just have W2 and 1099 income already reported to the IRS, and take the standard deduction. For most people, they can tell you what you owe. If it's wrong, you can tell them your dependents or filing status changed and get a new form. If you have a weird situation the IRS doesn't know about, you can still do your own taxes, but that's not most people.