The tax year beginning date determines which year business return to file.
For example, file the 2020 return for 1065, 1120, 1120-S, or 1041 for fiscal years that begin in 2020 and end in 2021. For a fiscal or short tax year return, fill in the tax year space at the top of the form.
See the "Period Covered" topic in the following instructions:
Note that any link in the information above is updated each year automatically and will take you to the most recent version of the document at the time it is accessed.