Maria 2.0
But for real, im assuming just go in with a list of Mtgox Withdrawals to cash, since what do they care how much BTC i have.
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Im in USA
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For this tax return, I can define the income as pure income, and still come out okay, since I have a $300 deduction left and and pay 10% on the rest.
But the smarter way would be to setup depreciation if applicable, and subtract utility bills, since next year my expected income is going to be off the charts.
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Would it be filing as a small business?
It is unlikely that they care how much BTC you have.. it is the cashing out part that they would care about.