PORTLAND — Mattress World owner Sherri Hiner says her business collapsed under the weight of a slow economy and a $2 million tax bill from the state of Washington.

The 15-year-old Portland company is closing seven stores. Two others are independently operated.

Hiner told The Oregonian newspaper she wasn’t aware she had to collect sales taxes on mattresses delivered to Washington residents if she didn’t have a store in that state.

Washington tax officials conducted an audit of her records back to 2003 and demanded the $2 million.