Return / Return back
UsageReturn normally already contains the idea of going or giving back, so return back is usually redundant in formal writing.
Return
Use when
You mean go back, come back or give something back.
Example
“Please return the signed form by Friday.”
Return back
Use when
Avoid back when it merely repeats the ordinary meaning already carried by return.
Example
“Replace 'return back the form' with 'return the form'.”
Quick check
return back, returned back
Usage note