Would'nt dare to do that myself. I know people who have been working, get paid in cash and put it into the bank and have had to repay the amount of cash that the tax would cost. If that happens it would be good if you also could prove that you've sold BTC and not been doing illegal stuff.

I would talk to the bank and pay the amount of tax just to be on the safe side, dont want to get in trouble with the government.....but i may just be a coward.