The 33-year-old, who played the role for five years between 2000 and 2005, is the first in a wave of "stunning new signings" that will inject a new lease of life into the show when it's revamped over the coming months.
The announcement comes two months after producers revealed that Jeff Hordley was returning to the soap as Charity's cousin and former lover, Cain Dingle.
Cain reappears in Emmerdale in April and Charity is due to return with her five-year-old son Noah in a blaze of glory shortly afterwards, to the shock of her daughter Debbie (Charley Webb).
Speaking of her decision to reprise her role, she said: "Charity is a wonderfully complex character and an absolute joy to play. I couldn't resist the opportunity to explore a new era of Charity, Cain and Debbie and will relish seeing what she's been up to since we saw her last."
Series producer Gavin Blyth added: "It's going to be an incredibly exciting year for Emmerdale with Charity and Cain back at the heart of the action.
"This is the first in a series of new signings and intriguing characters on the horizon and we're going to delight in reminding viewers that when it comes to compelling drama and commanding characters, Emmerdale is a force to be reckoned with."
Charity first appeared in Emmerdale in March 2000 for her cousin Butch's funeral, but it later emerged that she was a prostitute on the run from the police. She quickly went on to marry millionaire Chris Tate in 2001, before having an affair with her sister-in-law Zoe.
When Chris died after drinking a poisoned glass of champagne in 2003, it soon transpired that he had committed suicide in an attempt to frame Charity for his murder.
She later went on to have a relationship with Tom King, but on their wedding day, Tom was shown some damning photos of Charity kissing Cain by Sadie, who had hired Cain to set her up.
Charity was last seen on screen in March, fleeing the village with her one-year-old Noah after exacting her revenge on Sadie King (Patsy Kensit) by having a fling with her husband Jimmy King (Nick Miles).
Atkins will begin filming and reappear on screen later in the year.