Home Bitcoin mining with solar energy in Spain: taxation
Mining = economic activity (if habitual): Requires self-employment registration (autónomo), declare income as business income, deduct expenses.
Mining income: Each BTC mined = business income at market value when received. Same price = acquisition cost for future sales.
Deductible expenses (as autónomo): ASIC/GPU depreciation, electricity consumption (mining portion), self-employment fees, maintenance.
Solar energy: Electricity production cost = deductible. Excess sold to grid = additional taxable income.
Occasional mining: May qualify as capital gain (not business activity) — frontier not clearly defined by AEAT.
kointax correctly classifies mining income as business activity income.