Social Security Retirement/Disability/Survivors benefits are reported on a form SSA-1099 and the benefits received are to be entered on a federal tax return. The benefits may be taxable depending on the amount of other income you have entered on your tax return.
However, if the Social Security benefits are the Only income to be reported on the tax return, then there is no reason or need to file a tax return.

If Social Security is your ONLY income you do not have to file a tax return.  Except----did you receive both stimulus checks?   If you did not receive them then you can file a 2020 return to use the recovery rebate credit to get the stimulus money..