You have to file a tax return because you’re probably a taxpayer. The IRS considers taxable income as all income from whatever source derived, including gains realized, unless otherwise excluded.
To prepare your taxes on your own, you’ll need to assemble the correct paperwork. That includes all of those forms that have been coming in from various sources.
When you begin tallying your income earned for the year, you will eventually end up with your “gross” income from all sources.
If you work as an employee, your employer will send you a Form W-2 in the mail and possibly electronically. This documents all the details related to your pay, deductions, and other elections made during the tax year.
Aside from having certain types of income, the IRS awards better taxation preferences. You have two levers to lower your taxable income: tax deductions and tax credits.