You should see the year clearly noted whenever you're filing taxes. It's on each IRS form you'll file. If you're using tax software, the tax software should remind you of the tax year throughout the process. No matter whether your tax year is the same as your calendar year, you will always file taxes for the prior year. Taxes for the 2021 tax year will be filed in the 2022 tax year, regardless of how you define your tax years.