The 'Smile' pop singer announced on Sky News this morning that her last concert will be at London's O2 on March 7.
Speaking alongside Wayne Hemingway, Allen revealed that she would be working on the designer's Vintage At Goodwood project and her own Lucy In Disguise range.
"I'm helping Wayne out with this first of all and then I'm opening up a shop with my sister and a couple of other people and I'm really busy," she said. "I'm in the office every day, sourcing clothes and getting really excited about my new venture."
Hemingway added: "She's here to bring fashion back in. She's got a new business called Lucy in Disguise, which is about vintage clothes democratising fashion, and that's what Vintage at Goodwood is about as well. It's about bringing music and fashion back together.
"The Sex Pistols couldn't have happened without Vivienne Westwood. The swinging '60s couldn't have happened without Carnaby Street. The New Romantics couldn't have happened without the Blitz Club. Now all we seem to have is music and no wonder the music industry isn't doing so well... You cannot separate fashion and music."
Allen won the 'Giving It Back Fan Award' at last night's NME Awards.