You don't cut off a toe.... You cut the web between the toes.
Now, Havi. You can probably still toe punch them, i have seen someone toe punch full grown chickens so they could tell them from the others that resembled them, it just bled a little more is all. It's best to do it as soon as they hatch, or a few days later but a week old shouldn't hurt. Personally i don't like the toe punches, more difficult and i just use cuts through the web. Toe punches can heal up or split, splitting is a bad thing since i use cuts which then can leave the bird ending up being marked just like another bird.
I just use small scissors you'd use for trimming your nose hair, just a quick snip through the web and all is over. It usually happens too fast for the chicks to really register it and if done early enough, rarely bleeds.