The regulations for which gains or losses count as private sales transactions are set out in section 23 of the Income Tax Act. For tax purposes, they are classified as other income.
Specifically, the following transactions are considered private sales transactions:
Other assets include items such as gold bars, gold coins, foreign currency, or rented transport vehicles.
Cryptocurrencies can also be the subject of a private sales transaction according to section 23 (1) no. 2 of the Income Tax Act. This means for transactions within private assets: Capital gains from the exchange or re-exchange of Bitcoins, etc. into euros or another cryptocurrency are considered taxable speculative transactions if the purchase and exchange occur within one year. A gain is (only) tax-free if it is below the allowance of 600 Euro.