If your business involves mailing items, sending invoices, or shipping products, those costs are deductible. Postage, shipping fees, courier charges, and the cost of packing materials used for business purposes are all ordinary and necessary business expenses. If you sell physical products and ship them to customers, the full cost of that shipping is deductible. Costs for a PO box used for your business also qualify. Personal shipping costs, like mailing a birthday gift or shipping items you sold through a personal garage sale, are not deductible.