@gentlemand how does the taxman find about these trades if the person doesnt disclose it?, or do taxmen get inputs from the exchanges regarding these transaction can you clarify this part?.
It varies from country to country but the IRS in America has contacted exchanges asking for user details and the British equivalent will soon as well.
You may well be fine not disclosing anything but there's no telling what the future holds. One day there might be software that links you to everything you've ever done in cryptoland in less than a second and spits out a bill.