Capital gains are taxed differently around the world. Switzerland is unusual in that private investors pay no capital gains tax on securities held in their own name (dividends are taxed as income, but realised price gains are not). Germany taxes them at the 25% Abgeltungsteuer, France includes them in the flat tax (30% including social contributions), Italy at 26%.
Even in Switzerland, the 'professional trader' classification can drag capital gains into taxable income. The criteria include holding period under 6 months, high turnover, use of leverage and short-term trading dominating total income. Most buy-and-hold ETF investors easily fall in the private-investor camp; day traders should review the criteria carefully.
Capital gains can be realised (sold) or unrealised ('paper'). Tax obligations arise only on realisation. Long-term wealth building therefore favours minimising turnover — selling triggers tax leakage that compounds against you. Tax-loss harvesting (selling losers to offset winners) is more nuanced in Switzerland because losses do not offset taxable income for private investors.
A Swiss investor buys 100 shares of Roche at CHF 240 (CHF 24,000) and sells five years later at CHF 290 (CHF 29,000). Capital gain: CHF 5,000, taxed at 0% if she qualifies as a private investor. The CHF 5,000 is added to her wealth subject to cantonal wealth tax.