For an S corporation - do I have to physically dispose of the inventory to write it off?

I plan to write down some obsolete inventory by taking it out of inventory and letting the expense flow through COGS.  My question is do I have to physically remove, donate, destroy the inventory to write it off or can I keep it and hope to sell it in the future.  We are an S Corporation.  Also, can you point me to the IRS publication that addresses this issue. Thanks!