Every part of your statement is wrong. 1) Selling used goods at a loss is not deductible on your tax return unless you are in the business of selling used good

Every part of your statement is wrong. 1) Selling used goods at a loss is not deductible on your tax return unless you are in the business of selling used goods. 2) Unless you are selling a lot of tangible goods (i.e., you have a business selling things), you aren't even eligible to register for sales tax in most U.S. states. 3) If tax applies to the sale of a used good in this situation, it would be a use tax that is the responsibility of the buyer to report and pay.