Cryptocurrency awarded as staking rewards is in principle taxable on the date you received the cryptocurrency in your portfolio and can use it.
As a result, you have to calculate the value of your staking rewards on the award date. The cryptocurrency awarded is taxed as personal income and you must declare the value in box 20 of your tax assessment notice (årsopgørelse).
If you retain the cryptocurrency awarded in order to make a profit on resale, this will in principle be speculation. You must therefore declare any gain or loss when you sell the cryptocurrency.
Read more about speculation here under (Calculate your transactions).
If you sell your awarded cryptocurrencies, you have to calculate whether you have made a gain or loss according to the FIFO principle, and together with your other cryptocurrency holdings.
Read more about the FIFO principle here under Calculate your transactions.
Read a relevant decision (in Danish)
Cryptostaking - rebase rewards (SKM2022.323.SR)