Typically, the filing deadline to claim old refunds falls around the tax deadline of April 15. However, the 2020 filing deadline was pushed to May 17, due to COVID-19, making the three-year window deadline for 2020 unfiled returns May 17, 2024.
The IRS provides help filing your past due return.
For filing help, call 800-829-1040 or 800-829-4059 for TTY/TDD.