Give a stream of consciousness and then the final answer. Erin is portrayed by Ellie Kemper. She is an original character, although her closest equivalent in the British version of the series would be Mel the receptionist, who appears briefly in The Office Christmas specials, as Dawn Tinsley's replacement.

Answer this question: who plays the new receptionist on the office?
This is the relevant information: Erin is portrayed by Ellie Kemper.
So, the final answer is Ellie Kemper.