I took a medium length passenger mission 6.5 kLy and the area I am in now had at least three Untagged systems on the route. I did not scan them and left them for someone else to do the deed. The first one was about 600 Ly from Sol and SWOILZ CM-T D4-21 is about 800 Ly (The main star is tagged but two others are not.).
Enjoy.
Enjoy.