The year of the tax return should correspond to the year on your
W-2 or
1099 forms.
If you didn't receive any
W-2 or
1099 forms (such as if you owned a business), just make sure you choose the year edition that matches with the year during which you made the income and had the expenses or deductions you're planning on entering.
If you need to file a tax return for a prior year, go to the
Prior Year page and choose the year.