Where does it say 'You Are Already Enlightened'? I've heard Zen Buddhism characterised by the notion of 'Everyone is already enlightened'. Is that correct? - does Zen Buddhism actually say that and if so can someone give a reference to a text where it actually says that or something like it.

Many thanks as always
It's a basic Mahayana doctrine, important in other schools as well as Zen. 


  Hongaku is an East Asian Buddhist doctrine often translated as
  "inherent", "innate", "intrinsic" or "original" enlightenment... It is
  first mentioned in the Awakening of Faith in the Mahayana scripture.


https://en.wikipedia.org/wiki/Hongaku

Wikipedia also says it can be traced back to sayings of the Buddha in the Anguttara Nikaya: https://en.wikipedia.org/wiki/Buddha-nature#Earliest_sources