Taris comes at a different time for the republic than for the empire.
For the republic it's the 16 to 20 planet, the first after the capital planet.
For the empire it comes much later.
Edit: I'm already dreading the next time I have to go through Taris.
It's rakghouls everywhere. Rakghouls Rakghouls Rakghouls.
Go there and get this stuff. Why? Rakghouls.
Go here and kill these pirates. Why? Rakghouls.
Go buy these bagels and eat them. Why? Rakghouls.
I HATE RAKGHOULS!
LOL I was just looking at the the planets wondering if I spelled the planet name wrong or something.