METZINGEN, Germany — Buyout firm Permira Advisers is set to make about twice its original investment in Hugo Boss AG as it sells its remaining stake in the German retailer, according to a person with knowledge of the matter.

Permira on Monday said it will sell a 11.9 percent stake, or 8.4 million shares, in Hugo Boss. The sale will be priced from 112.5 euros to 113 euros and Permira has demand for all the shares on offer, a second person said, asking not to be identified as the transaction is private.

The sale of the stake, valued at as much as 996.2 million euros ($1.1 billion) comes on a day when Germany’s benchmark DAX Index passed 12,000 for the first time, with gains for companies benefiting from a stronger consumption trend in the country. Hugo Boss has gained 30 percent in the last 12 months.

The retailer, based in Metzingen, Germany, this month forecast 2015 profit below analysts’ predictions on cooling demand for luxury clothes and accessories in Europe and China.

Permira inherited the stake when it bought a majority holding in 2007 in Milan-based Valentino Fashion Group SpA, Hugo Boss's parent company at the time. It sold the Valentino assets to a group led by Qatari investors in July 2012.

The investor has over the last two years been cutting its holding in the fashion house. Last month it sold a 10.4 percent stake to the market, and a further 500 million euros to Italy’s Marzotto family.

A spokeswoman for Permira declined to comment.

By Ruth David, Kiel Porter, with assistance from Sarah Jones. Editors: Aaron Kirchfeld, Elizabeth Fournier, Mohammed Hadi.