Tax on T-bills or Zero coupon bonds

are these considered capital gains and therefore no tax as private investor or is there some sort of imputed income tax? also any difference in tax treatment if sold before maturity?

As a general rule, Swiss tax practitioners consider US investments with 1099s to be taxable in the current year in CH.

Take it with a grain of salt, but I believe that income tax (for a non professional investor) are applied on the coupon and not actual gain. On top of that zero coupon bonds might be taxes on the whole value of the bond as income - so you need to be extra careful there.

In general the difference in taxing dividends vs capital gains in Switzerland makes dealing with bonds very messy, so you need to know well what you are doing or you can end up paying more taxes than real dividends.

If you sell before maturity - you probably won't pay any taxes, since it's all capital gain and not dividends. However, if the tax office sees a pattern of tax avoidance they can insist on your paying taxes on the virtual dividends that you are avoiding

This is determined based on the data-at-issuance so you should be able to answer that before you buy, last year's data also apply going forward.

The criteria is, if more than 50% of the expected annualised performance comes from capital gains it's taxed as income, regardless of your performance.

has anyone had real experience of the correct tax treatment of zero coupon bonds? and not just their thoughts (googling this seems to have no concrete answer)

eg. If I buy T-bill at $90 redeem at par $100, gain of $10. is this $10 considered capital gain and not taxed or income tax is applied?

there's another thread on this. iirc, it will be taxed as income.