I purchased a pre-owned phone on Swappa to use temporarily. After a few months, I resold it on the same platform for a price that was $20 less than what I had paid for it. However, I am confused as to why I am being charged sales tax for a second-hand item. I am not a business or professional seller, and I sold the phone for a lower price than what I originally paid. From what I have researched online, it seems that sales tax is not required in my situation. I am considering consulting with a CPA firms to get further clarification on this matter.