There are different tax laws in each country, regarding digital currencies, just like stocks and commodities. The difference between stock exchanges and crypto exchanges is that most stock exchanges register the gains and losses automatically and send in the necessary information to the IRS (Different from country to country). You are bound to pay taxes on your gains, and you are able to deduct your losses. Keeping track on every trade on every exchange is close to impossible. Thankfully there are some great tools to help you.