Doctor Who Series 4 (in-universe)

Doctor Who Series 4 was the fourth of twelve series of Doctor Who available on BBC iPlayer by May 2020. (WC: The Zygon Isolation)

Behind the scenes
Turn Left (an episode which is part of the real world series four) does exist in the Doctor's universe, but there's yet to be any confirmation in any valid source that Turn Left is part of the in-universe fourth series of Doctor Who.