UPDATE 2-Saks offers up to $100 million in common stock

* Offers up to $100 mln in common stock

* Will use proceeds to pay down debt, and corporate use

* Shares flat after hours (Adds details on debt and shares outstanding)

SEATTLE, Sept 29 (Reuters) - Saks Inc (SKS.N) is offering up to $100 million in common stock, the upscale store operator said in a regulatory filing on Tuesday, and its shares fell 4.6 percent in after-hours trade.

The company, known for selling designer brands, said it would use proceeds from the offering to pay down debt and for general corporate purposes.

Saks said in the filing with the U.S. Securities and Exchange Commission that it had roughly 138.3 million shares of common stock outstanding as of Sept. 28, and long-term debt and lease obligations of about $662.9 million as of Aug. 1.

Saks, with 53 Saks Fifth Avenue stores and 54 OFF 5th stores, has been cutting costs and inventory to offset a decline in luxury goods sales.

Saks shares, up about 64 percent so far this year, fell in after-hours trading to $6.84 before returning to $7.17, where they had closed on the New York Stock Exchange. (Reporting by Aarthi Sivaraman in Seattle; Editing by Gary Hill)