What is Selling Short Against The Box?

Selling short stock that is actually owned by the seller but held in the box, meaning it is held in safekeeping. The seller borrows securities needed to cover as the stock in the box may be inaccessible, or the seller may not wish to disclose ownership. The traditional motive for this transaction was to defer capital gains taxes. However, this method became infeasible under the Taxpayer Relief Act of 1997.