The real hassle in Belgium is that crypto is treated as securities capital gains, so technically you have to declare it even for small amounts, but the thing nobody mentions is archiving EVERYTHING - every transaction on Kraken, every wallet transfer, the fees - because if the tax authorities ask questions you're going to have a nightmare reconstructing all that later. For losses, you can offset them against gains from the same year, but it's not really a free deduction like it is for other sectors. Honestly, I'd suggest checking with a Belgian accountant who specializes in crypto because it's really an area where the rules change fast and you don't want to end up in a grey zone.