Does Witch Bolt deal the added 1d12 damage on the turn that it’s cast?

Assuming that Witch bolt is cast at 1st level and hits the target would the target take 2d12 damage in that turn because its the beginning of the spell’s duration and

"on each of your turns for the duration, you can use your action to deal 1d12 lightning damage to the target automatically."

or does it take effect the turn after you cast it?