Bauer Media, which publishes magazines including Grazia, Pop and Arena Homme, is launching the website which is invitation only.
Members will be able to buy women's premium brands at lower prices for a limited period.
Each sale will be announced to members in advance via email and focuses on one specific designer brand for 48 hours only.
The website also includes articles on fashion and fashion advice.
Cocosa brand director Frances Card said: "Our brand relationships allow us to offer fantastic selection and styles to our deserving and discerning members who in turn can buy these very special pieces at very special prices."