good question, but that's a misconception (one of the reasons I started looking at crypto seriously haha). Depending on what kind of asset crypto is defined as in your country, you might actually have to be able to prove not only the amount you put in and took out, but also every trade you've done. I don't have my references at hand and would love to give you more info, but the main thing I got from my research is that you can still get taxed. But if you're bringing less than 10k eur/usd into your account at a time you'll be fine (doesn't ring any alarms at the bank).
Other misconception, crypto is actually traceable. Because every transaction is immutably recorded on the blockchain it makes it even more transparent. That said, it is some work to retrieve that data, but easier than with conventional funds. Obviously cryptos like XMR and DASH work differently for that very reason.
Here's a good post by @nanzo-scoop with some good thoughts and cautions about taxes and crypto.
https://steemit.com/cryptocurrency/@nanzo-scoop/vlog-lets-talk-about-the-elephant-in-the-cryptocurrency-room-taxes
Good luck!