The alcoholic mother-of-three was seen leaving the village to live with her sister and her daughter Lacey (Georgia Bourke) in scenes which screened on E4's first look screening of the soap on November 7.
Carli, 39, tweeted: "I'm so sorry I couldn't tell you all!!!" and thanked fans for their farewell messages.
Martha left on a high after helping to save psycho killer Will Savage's hostages and bring him to justice.
Carli told Digital Spy: "I absolutely loved working with all the Kanes - every scene was a treat, particularly the emotional ones as they are all such wonderful actors.
"I was originally only meant to be in Hollyoaks for a few episodes, so to be asked to stay for two years was a blessing.
"Hollyoaks is going from strength to strength and I shall be watching the Soap Awards next year to see how many awards we get. I shall now enjoy a little time at home with my daughters baking cakes."
Martha was introduced to Hollyoaks in early 2012 as the mother of Ash and Callum, who were both recently killed off.
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