These crypto tax articles become less and less relevant in the coming tax year as people are going to be filing losses, not gains. I expect headlines like “How to make sure you add up your crypto losses to the full amount”
I'm no expert, but from what I understand, you can't deduct losses from regular currency deposits, either.
Here is a decision from the Supreme Administrative Court in a case where someone had converted 460 000 EUR to USD and later converted them back to EUR with a loss of 30 000 EUR and wanted to deduct the loss from their capital gains tax (Finnish): http://www.kho.fi/fi/index/paatoksia/vuosikirjapaatokset/vuo...
It was denied as there is no clause in the Income Tax Act allowing such a deduction.
Tax Administration guidance (Finnish): https://www.vero.fi/syventavat-vero-ohjeet/ohje-hakusivu/489...
Income Tax Act (Finnish): https://www.finlex.fi/fi/laki/ajantasa/1992/1992153