eBay charges sales tax according to the law of each state that requires them to do so. They determine if an item is taxable or not based on the first (or only) category that the item is listed in. So for example, if a sports jersey is listed under a Clothing category, then it won't be taxable if clothing isn't taxable in your state. But if it is listed under Sporting Goods or Collectibles, and those items are taxable, then it will be taxable.
If you think an item is not in the correct category, you can ask the seller to change it. If you feel you have been charged tax on a non-taxable item, you can ask your state to refund it, or you can deduct it from the Use Tax that you have to pay on non-taxed purchases.
Many states require that sales tax be charged on the shipping as well as the purchase price.
https://www.avalara.com/us/en/learn/whitepapers/shipping-handling-sales-tax.html
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The following states usually consider charging shipping that is part of an order a taxable activity, regardless of whether sales tax is part of the price or not:
Arkansas, Connecticut, District of Columbia, Florida, Georgia, Hawaii, Indiana, Kansas, Kentucky, Michigan, Minnesota, Mississippi, Nebraska, New Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Pennsylvania, South Carolina, South Dakota, Tennessee, Texas, Vermont, Washington, West Virginia, Wyoming.
All online marketplace facilitators are required to charge sales tax the same way, eBay is no different.
