Readers can also win an array of prizes, including designer accessories created especially to mark the anniversary.
At 252 pages, the birthday issue is the biggest of the year, and advertising volume is up 9% compared to last year's October issue, say the publishers. Model Daisy Lowe guest edits in the issue's high-street special, while anniversary-themed content includes photos of the InStyle team aged ten and an interview with cover star Diane Kruger, who celebrated her own birthday on the shoot.
The ten brands offering readers £10 off purchases include Karen Millen, Nine West and Banana Republic. Readers can also win a week's worth of glam dresses showcased in a fashion shoot, and a £4,000 spree at my-wardrobe.com.
The designer accessories created just for InStyle's tenth birthday include purple ponyskin platforms by Sergio Rossi, a crystal necklace by Atelier Swarovski and a Coach bag. Readers can win the limited edition products and they will also go on sale. Meanwhile, the fashion house elite have created one-in-the-world bottle designs of their iconic scents, which InStyle is auctioning in aid of the charity Mothers4Children.
InStyle editor Eilidh MacAskill says: "I'm thrilled to be editing this tenth birthday issue. The team and I adore the fact we get to create the world of InStyle with every tweet, web story and magazine. For our birthday, we wanted to reward our readers and that's why this issue is jam packed with amazing competitions and discounts off genius brands."
Publisher Sarah Hammond adds: "InStyle is continually building as a brand and has firmly established itself in the world of fashion and beauty. Our new franchises have attracted high-profile fashion partners and we have exciting plans for the rest of the year and beyond."
InStyle's tenth birthday issue is on sale from 8 September. InStyle is supporting the issue with advertisements on www.instyle.co.uk, www.look.co.uk, www.marieclaire.co.uk, and www.nowmagazine.co.uk, while brands including Urban Outfitters and Nine West are promoting the issue to their customers.
