There is no advantage, from a tax perspective, to writing off inventory as opposed to donating it.
Either way you handle it, you will receive a deduction via cost of goods sold (COGS), for the cost of the inventory.
When you enter your inventory purchases and ending inventory, TurboTax makes the calculation of "COGS cost" for the year based on these numbers and you beginning inventory. If you do not include the cost of the items donated, written off, or expired in your ending inventory, these items will automatically be included in COGS.
Note: You will not include the cost of these items as "donations" or "write downs" separately on your schedule C.
