The long time EastEnders favourite, played by Jessie Wallace, will make her return later in the year.
But it will be far from straight forward, with a number of "twists and turns" planned as part of a "very emotional storyline".
“Kat’s return has caused a lot of excitement, but it won’t be quite what everyone’s expecting," an insider told The Sun newspaper. “Rather than her friends and family rolling out the red carpet the residents are told she has died. It’s set to be a very emotional storyline — but that’s probably fitting for Kat.
“It won’t all be quite as it seems and the writers have some further twists and turns planned.”
EastEnders' executive producer John Yorke first announced Kat's return in December.
Jessie said: "I am thrilled to be returning to EastEnders next year and knowing what John Yorke has in store for the Slaters is incredibly exciting.
"I love Kat and Walford dearly and I cannot wait to get started - watch out Walford, Kat's coming home."
Alongside Kat, Big Mo and Jean Slater - played by Laila Morse and Gillian Wright respectively - will also be returning.
"I'm really excited to be coming back," said Laila. "It's the one question I'm constantly asked. I can't wait to see everyone and get stuck back into life in Walford."
Gillian added: "I am delighted the Slater women are to be reunited once more.
"I have always adored working alongside Lacey, Jessie and Laila and I am looking forward to being reacquainted with everyone at EastEnders again."