For Self Employed activities the income reported on Schedule C of your tax return would be the sales price to the customer. The price you paid to purchase the item for resale would be considered an expense and reported as Cost of Goods Sold. So if you sold an item to your customer for $18 and your price to purchase that item for resale is $15, then the net income on which you will be charged tax is $3. You will pay income tax as well as self employment tax on the net income for the business.
