Bitcoin and tax
A (growing) overview of the relation between Bitcoin and tax.
Filing Bitcoin taxes
In countries without capital gains tax where Bitcoins are regarded as assets it seems fairly easy. You calculate the total sum of Bitcoin on December 31st and use your favorite exchange for conversion into your national currency, although it's more likely you'll have another conversion through USD.
If you're keeping your altcoins in exchanges it's relatively easy as most exchanges (at least Bter and cryptsy) are showing the total value in BTC. You can simply take this value instead of going through calculating this by hand or by going through the USD value from coinmarketcap and then again later to your national currency. It's much easier to take the BTC sums and calculate the value in your national currency afterwards.