No plot details have been revealed although the end of season three suggested the return of Sherlock's arch-nemesis Moriarty.
Starring Benedict Cumberbatch as the titular character along with Martin Freeman as sidekick Dr Watson, the show – which first aired in 2010 – is a contemporary take on the classic books by Arthur Conan Doyle.
Benedict Cumberbatch as Sherlock Holmes
At 2.21pm on Wednesday - a reference to 221B Baker St where Sherlock Holmes lives - the account tweeted: "Miss me?" , the hit drama, will return for a Special, followed by a series of three new episodes. "
Later tweets asked: "...why is Moriarty's face being broadcast on every television in the land? " in reference to the end of season three.
In April, Martin teased fans about the idea of a special episode.
"Mark Gatiss may beat me up, but there is an idea for this one-off special that's such a good idea, and as I was listening to it I thought, 'We've just got to do this'," Martin told Alan Carr during an episode of Chatty Man.
"And I don't know when we are going to be able to do it, unfortunately", he added, before continuing: "It's a fantastic, really mouth-watering idea. But I really don't know when we are going to get to do it."
Benedict Cumberbatch and Martin Freeman filming season three of Sherlock
It appears though that the production team behind the show have found the right time, and the special episode will film early in 2015. This has led many fans to suggest that it could air Christmas 2015, with season four airing in summer 2016.
Rumours have also been swirling that the one-off episode will be set during Christmas.
This also corresponds to comments made by Mark Gatiss, who has made no secret of the fact that the Yuletide story The Blue Carbuncle is among his favourite of the Sherlock Holmes adventures.