We have a very specific tax law for second hand items. When selling second hand items, you don't need to charge tax on the full price, but rather on the profit amount.
Example: I bought a product at 50euro and I am now selling it for 60euro. The tax I have to charge is not 21%, based on 60euro, but 21% based on 10euro (60euro - 50euro). So my final price would be 60euro + 2,10euro = 62,10euro.