Quote from: raulillo on February 17, 2016, 10:08:00 PM

Case A) Let's say I buy BTC mit EUR today (February 2016), and immediately buy an altcoin with them. I keep them in a safe (coldwallet) and eventually cash them back to BTC in, let's say November 2016. Ideally I'll have quite some more BTCs than at the beginning. When can I cash them back to EUR free of tax? Still February 2017 or November 2017?

I would handle it like this (I try it to explain by an example):
You bought 1 BTC for 100 . Bought an Altcoin for 1 BTC on Feb 2016, sell the Altcoin on November 2016 for 1,1 BTC.
You didn´t hold them longer than one year.

If the price is still the same..

earning - buyprice = profit
1,1 BTC * 100 - 1 BTC * 100 = 10 Euro profit

It gets funny if the BTC price rises to 150 Euro / BTC, but here im not sure
Case A)
1,1 BTC * 150 - 1 BTC* 100 = 65 profit -> new buyprice for 1,1 BTC 165 Euro
or
Case B)
0,1 BTC * 150 = 15 profit -> New Buyprice = 1,0 BTC for 100 + 0,15 for 0 = new buyprice for 1,1 BTC 100 Euro

You got the BTC on Nov 2016 so you must wait until Nov 2017 to sell them.

Quote from: raulillo on February 17, 2016, 10:08:00 PM

Case B) Similar to B, but instead of keeping the altcoin safe in a coldwallet, I'm trading with them for months long. Eventually converting to/from BTC/altcoin(s) back and forth. In November 2016 I decide I've won/lost enough and want to trade back to EUR. Which date would make this taxfree? February or November 2017?

After each trade with full amount of btc the "free-Tax"-Timer resets.

You must provide them everything, if you hold the coins for over one year. Then its enought to show them your BTC-Wallet with the date of deposit. If you trade them you can try to send them the summary of your trading in one sheet with your profit / loss. But maybe they wanna see each trade @ an excel-sheet.

This is my opinion, handle with care